Automobile Ride, Handling, and Suspension

Automobile Ride, Handling, and Suspension Design

With Implications for Low-Mass Vehicles

When carried to the extreme, today's emphasis on automobile mass reduction has significant implications for vehicle ride and suspension design. We therefore review traditional automobile suspension systems and offer comments on the special considerations of suspension systems of extremely low-mass passenger cars.

The ride and handling characteristics of an automobile center on the characteristics of the tires. Tires are the vehicle's reaction point with the roadway. They manage the input of forces and disturbances from the road, and they are the final link in the driver's chain of output commands. Tire characteristics are therefore a key factor in the effect the road has on the vehicle, and in the effectiveness of the output forces that control vehicle stability and cornering characteristics. The tire's basic characteristics are managed by the system of springs, dampers, and linkages that control the way in which tires move and react to disturbances and control inputs.

The bounce and steering movements of the wheels provide for a variety of simultaneous needs. They provide steering input for directional control, they compensate for (or utilize) body roll to improve cornering ability, and they move vertically in response to roadway irregularities in order to smooth out the ride and maintain adhesion. Wheels are connected to the sprung mass through linkages and are therefore affected by the rolling and pitching movements that occur about the suspensions system's reaction centers. The mechanical requirements for directional control, cornering forces, and ride comfort are continuously changing according to roadway and driving conditions. The suspension and steering linkages are designed to allow the wheels to move as needed to meet the dynamic requirements of various combinations of events. However, the designer is normally constrained by mechanical conflicts between structural members, the engine and drivetrain, and other components that also must fit into the vehicle. Consequently, errors in geometry are common, and the actual suspension system often falls short of the ideal in a variety of ways.

Ride Comfort

The quality referred to as "ride comfort" is affected by a variety of factors, including high frequency http://www.rqriley.com/suspensn.html (1 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension vibrations, body booming, body roll and pitch, as well as the vertical spring action normally associated with a smooth ride. If the vehicle is noisy, if it rolls excessively in turns, or lurches and pitches during acceleration and braking, or if the body produces a booming resonance, occupants will experience an "uncomfortable ride."

The ride quality normally associated with the vehicle's response to bumps is a factor of the relatively low frequency bounce and rebound movements of the suspension system. Following a bump, the undamped suspension (without shocks) of a vehicle will experience a series of oscillations that will cycle according to the natural frequency of the system. Ride is perceived as most comfortable when the natural frequency is in the range of 60 to 90 cycles per minute (CPM), or about 1 Hz to 1.5 Hz. When the frequency approaches 120 CPM (2 Hz), occupants perceive the ride as harsh. Consequently, the suspension of the average family sedan will have a natural frequency of about 60 to 90 CPM. A high-performance sports car will have a stiffer suspension with a natural frequency of about 120 to 150 CPM (2 to 2.5 Hz).

Originally, human sensitivity to ride frequency was believed to be associated with the natural oscillations of an adult human body during a walking gait. An adult walks at the rate of about 70 to 90 steps per minute (frequency), and the torso moves up and down about 2 inches (amplitude) with each step. Early designers therefore attempted to constrain vehicle oscillations to those limits, the ride was indeed comfortable, and the theory was therefore believed to be correct. Today, our information about human sensitivity to vibrations is more sophisticated. We know that amplitude affects human sensitivity to frequency, and that there are some frequencies that are especially uncomfortable. For example, a frequency in the range of 30 to 50 CPM will produce motion sickness. The visceral region of the body objects to frequencies between 300 and 400 CPM. The head and neck regions are especially sensitive to vibrations of 1,000 to 1,200 CPM (18 to 20 Hz). These are the types of vibrations that are likely to emanate from the tires or from axle hop. Longitudinal oscillations are sensed primarily in the torso. Surprisingly, humans are most uncomfortable with longitudinal vibrations in the 60 to 120 CPM range (the region of greatest comfort for vertical vibrations). Discomfort from longitudinal disturbances occur when the vehicle pitches or when the seats lean rearward at a higher-than-normal angle.

The perception of ride quality is degraded by virtually any disturbance experienced by the occupant. Human sensitivity varies according to the nature of the disturbance. Consequently, a "good ride" depends on the overall design of the vehicle, rather than just the design of the suspension system. To produce a comfortable ride, the high-frequency vibrations of wind and drivetrain noise must be minimized and properly isolated, and the suspension must be set in appropriate rubber mountings to isolate high-frequency roadway-induced vibrations. However, the natural frequency of the suspension system is still considered the cornerstone of a comfortable ride.

The static deflection rate of the suspension determines its natural frequency. Static deflection is the rate at which the suspension compresses in response to weight. Other factors, such as the effects of damping (shocks) and system friction, alter the natural frequency of the suspension system. However, the primary determinate is the undamped static deflection rate. If this rate is used in calculations,

http://www.rqriley.com/suspensn.html (2 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension results will likely be very close to the actual value needed for a smooth ride.

The static deflection rate of the suspension is not the same as the spring rate. Springs are located inboard of the wheels where they are normally subjected to the mechanical advantage of the suspension linkages. Static deflection is related to the distance the sprung mass (essentially the body) moves downward in response to weight. A static deflection of 10 inches in response to a weight equal to that of the sprung mass will produce a natural frequency of 1 Hz. A 5 inch deflection produces a 1.4 Hz frequency, and a 1 inch deflection results in a 3.13 Hz frequency. The natural frequency of a suspension can be determined by a simple formula expressed as follows:

NF = Natural Frequency in Cycles Per Minute (divided by 60=Hz).

SD = Static Deflection in Inches.

Implications of High Payload-to-Vehicle Weight Ratio

As vehicle mass is reduced, the payload-to-vehicle weight ratio naturally increases, which has trickle- down effects throughout the vehicle. An extremely low mass automobile, in the order of 1,000 pounds or less, for example, will have an unusually high payload-to-vehicle weight ratio.

Variations in payload affect the natural frequency of the suspension. The critical damping force also varies with load. Over-damping (above 100 percent) dramatically reduces ride quality. In order to avoid over-damping at light loads, some degree of under damping is usually accepted at the fully- laden weight. Also, a passive suspension in combination with a high payload-to-vehicle weight ratio require a relatively high static deflection rate (a stiff suspension) in order to avoid undesirable effects on vehicle ride height. Ride height refers to the height of the body at a given load. It is important to keep ride height variations within predetermined limits in order to maintain headlight dip angle, provide adequate suspension stroke, and to provide an appropriate ground clearance. Load naturally affects the standing height of the vehicle. As load increases, the vehicle rests lower on its suspension, and at lighter loads it rests higher. Heavy loads in the luggage compartment can affect the pitch of the vehicle.

The importance of a high payload-to-vehicle weight ratio becomes more apparent when the effect of payload on a standard sedan is compared to the effect of the same payload on a hypothetical ultralight vehicle. For example, a standard sedan of 3,500 pounds curb weight and a natural frequency of 1.2 Hz will rest 0.7 inch lower with the weight of two, 175 pound occupants aboard. The same static deflection rate in a 1,000-pound vehicle will cause the body to rest 2.45 inches lower with an equal, two-occupant load. A deflection of this magnitude will cause significant changes in the geometric relationship of suspension components. With a single occupant load, such a suspension would also

http://www.rqriley.com/suspensn.html (3 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension allow the body to list to one side. In order to equal the payload-induced deflection of the large car, the 1,000 pound vehicle must have a static deflection rate of 2 inches, which will result in a relatively stiff, sports-car-like ride of 2.2 Hz natural frequency. Consequently, an ultralight vehicle with a relatively high ratio of payload to vehicle weight will also have a relatively stiff ride. A self-leveling suspension and active damping could improve the suspension characteristics, but at higher cost and increased mass.

Payload variations can also have a much greater effect on the center of gravity of a low mass vehicle. Payload typically comes in human packages ranging from about 125 to 200 pounds each. A two- occupant load would therefore represent roughly one-third of the curb weight of a 1,000-pound vehicle. The same load amounts to only 10 percent of the curb weight of a 3,500 pound automobile. The effect of payload variations on center of gravity therefore becomes increasingly more significant as vehicle weight is reduced. Target handling characteristics of an extremely low mass vehicle should be based on the fully-laden weight.

The Ratio of Sprung to Unsprung Weight

Unsprung weight includes the mass of the tires, brakes, suspension linkages and other components that move in unison with the wheels. These components are on the roadway side of the springs and therefore react to roadway irregularities with no damping, other than the pneumatic resilience of the tires. The rest of the mass is on the vehicle side of the springs and therefore comprises the sprung weight. Disturbances from the road are filtered by the suspension system and as a result are not fully experienced by the sprung weight. The ratio between sprung and unsprung weight is one of the most important components of vehicle ride and handling characteristics.

Unsprung weight represents a significant portion of the total weight of the vehicle. In today's standard- size automobile, the weight of unsprung components is normally in the range of 13 to 15 percent of the vehicle curb weight. In the case of a 3,500 pound vehicle, unsprung weight may be as high as 500 pounds. A 500 pound mass reacting directly to roadway irregularities at highway speeds can generate significant vertical acceleration forces. These forces degrade the ride, and they also have a detrimental effect on handling.

Early pioneers believed that the primary job of the suspension system was to absorb bumps and smooth out the ride. Today we understand that an equally important function of the suspension is to keep the tires in contact with the road. This is not as easy as it might appear to be. When a tire encounters an irregularity the resulting forces tend to reduce contact pressure and therefore degrade adhesion. Obstacles impart a vertical acceleration to tires that increases in proportion to the forward speed of the vehicle and the size of the obstacle. The greater the accelerated mass (unsprung weight) the greater the kinetic energy. In a sense, a raised obstacle throws tires away from the roadway. A depression causes the surface to rapidly drop away leaving the tire to follow along when inertia can be overcome by the downward pressure of the springs. Both occurrences reduce the tire's contact- pressure and tires can actually become airborne if the forces are great enough.

http://www.rqriley.com/suspensn.html (4 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension The forces generated by roadway irregularities (bumps) must be overcome by the springs in order to keep tires in contact with the road. The force of the springs comes from the compressive load imposed by the weight of the vehicle. The lighter the vehicle, the less compressive force is available, and the easier it is for the vertical motion of the wheels to overcome the inertia of the sprung mass and transfer motion to it as well. The ideal combination occurs when the ground pressure is maximized and inertial forces are minimized by a high sprung-to-unsprung weight ratio. A high ratio keeps the tires more firmly in contact with the road, and it also produces the best ride.

The sprung-to-unsprung weight ratio is particularly important to the design of extremely low mass vehicles. The necessarily higher suspension frequency produces a rougher ride, which can be accentuated by smaller tires typical of smaller cars. Smaller diameter tires react more violently to bumps and potholes. Their reduced radius causes them to move deeper into depressions and climb more quickly over obstacles. The higher acceleration rates are offset to a large degree by the reduced mass of the smaller tires. Tests have shown, however, that smaller tires do in fact produce a rougher ride, even though they are lighter. With smaller, lighter vehicles, it is even more important to keep the ratio of sprung to unsprung weight as high as possible in order to reduce the undesirable effects of smaller tires.

When the ratio of payload to vehicle weight is exceptionally high, the fully laden weight provides the most valid basis for comparison. For example, the curb weight of Urbacar was only 650 pounds, which at the typical large-car ratio would have provided for a total unsprung mass of less than 100 pounds. At 23 pounds each just for the tire/wheel assemblies (exclusive of brakes, axles and suspension linkages), it is easy to see that Urbacar was far off the mark. However, the two-up weight of Urbacar was approximately 1,000 pounds. Using the two-up weight of both vehicles, the 500 pound unsprung mass of the 3,500 pound car (3,850 lb with two occupants) equates to a 130 pound unsprung mass for Urbacar, which is more in line with the actual weight of the components.

Regardless of the perspective, every component of the unsprung mass must be more closely scrutinized in low mass vehicles in order to keep unsprung weight to an absolute minimum. The advantages for the designer in this regard are that a low mass vehicle will impose significantly lower structural demands on components, and the lower operating speeds result in greatly reduced unsprung acceleration forces.

Cornering Dynamics

According to Newton's First Law, a moving body will continue moving in a straight line until it is acted upon by a disturbing force. Newton's Second Law refers to the balance that exists between the disturbing force and the reaction of the moving body. In the case of the automobile, whether the disturbing force is in the form of a wind-gust, an incline in the roadway, or the cornering forces produced by tires, the force causing the turn and the force resisting the turn will always be in balance.

Vehicle "feel" and handling characteristics have to do with the way in which the vehicle's inertial forces and the cornering forces of the tires act against each other. The magnitude and vector of the http://www.rqriley.com/suspensn.html (5 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension

inertial forces are established by the vehicle's weight and balance. In a turn, angular acceleration results in a force that is centered at the vehicle center of gravity and acts in a direction away from the turn center. The ability to overcome these forces and produce a controlled, stable turn depends upon the combined characteristics of the suspension and tires. The job of the suspension system is to support, turn, tilt and otherwise manage the tires and their relationship to the vehicle and the ground in a way that will maximize their capabilities.

The Tires In A Turn

At relatively low speeds (parking lot maneuvers) the vehicle turns according to the geometric alignment of the wheels. The wheels roll in the direction they are heading, and the vehicle turns about the point established by a projection of the front axles intersecting a projection of the rear axle. As speed increases, the actual turn center moves forward due to the slip angle of the tires. Click on Figure 1 below to retrieve a drawing that illustrates the location of the turn center.

Figure 1: Vehicle Turn Center (5k)

Slip angle is related to the lateral load or cornering force of the tire. As lateral loads increase due to higher cornering speeds, tires creep to the outside of the turn and therefore move in a direction that is different from their heading. The difference between the tire's heading and the direction of travel is called the slip angle.

Vertical load on the tires has an effect on the lateral cornering force generated at a given slip angle. In general, cornering force increases as the vertical load increases, but the increase is not proportional to the load. The tire's ability to develop cornering force, in relation to its vertical load, is known as its "cornering coefficient". Tire cornering coefficient declines as vertical load increases. However, the inertial forces of a vehicle in a turn increase in proportion to the increase in weight. Consequently, tires that are more lightly loaded can handle greater g-loads during turns, which is a feature that is especially relevant to the handling characteristics of low mass vehicles. The graph in Figure 2 shows the relationship between vertical load and cornering coefficient (click on the link to retrieve the image). The coefficient is determined by the percentage of rated load that is represented by the actual vertical load imposed on the tire. The graph in Figure 3 provides another way to view the relationship between slip angle, vertical load, and lateral cornering force.

Figure 2: Tire Cornering Coefficient (5k)

Figure 3: Tire Cornering Forces (5k)

Another cornering force comes from the tire's camber angle. When a tire rolls at a camber angle it generates a lateral force in the direction in which it is leaning. The lateral force is known as "camber thrust". The thrust produced by camber angle is much less than the force produced by slip angle. However, it can be a significant component of the total forces that contribute to vehicle handling

http://www.rqriley.com/suspensn.html (6 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension characteristics.

Oversteer and Understeer

The weight bias of the vehicle determines its inherent oversteer/understeer characteristics. A vehicle that is heavier at the front will tend to understeer and one that is heavier at the rear will oversteer. A vehicle in which the weight is equally distributed between the front and rear axles tends to exhibit neutral steer characteristics. Although the inherent understeer/oversteer characteristics of a vehicle are determined by its weight distribution, the design of the suspension and the selection of wheel and tire size can enhance or moderate those characteristics.

Understeer results when the slip angle of the front tires is greater than the slip angle of the rear tires. A greater steering angle is then required in order to maintain the turn. When the steering angle reaches full lock and the turn cannot be maintained, the vehicle drifts to the outside. In an understeer condition, the driver is attempting to negotiate a turn, but the vehicle mushes ahead refusing to cooperate. Oversteer produces just the opposite condition.

During oversteer, the slip angle of the rear tires is greater than the front. Consequently, the turn-rate increases on its own and the driver therefore reduces the steering angle to compensate. During severe oversteer, the steering angle may reach full lock in the opposite direction while the vehicle continues on into the turn. The vehicle is then said to "spin out." A vehicle that understeers is considered safer in the hands of the average driver.

An obvious solution to the negative effects of understeer and oversteer would seem to be that cars ought to be designed for neutral steer. Neutral steer is the theoretical ideal in which the slip angle of front and rear tires increase in unison throughout the range of steering angles. Unfortunately, the factors that influence vehicle dynamics are not so precisely manageable. With the slightest encouragement, a car with neutral steer characteristics can easily cross over into an oversteering condition. Consequently, designers prefer to create some degree of understeer in order to avoid oversteer.

Tuning the Suspension of a Completed Vehicle

When the suspension is designed, certain handling characteristics are targeted. However, mechanical compromises, errors, or limitations of the art may result in a vehicle that does not handle precisely as intended. Even after the vehicle is finished, the suspension can be tuned for different cornering characteristics. The variables available for tuning the suspension include changes in tire and rim size, tire inflation pressure, and the stiffness and location of the anti-roll bar.

The anti-roll bar is essentially a transverse-mounted torsion bar designed to reduce body-roll during turns. It exerts no influence on the suspension when wheels bounce in unison. If vertical movement on one side exceeds the vertical movement on the other, the anti-roll bar exerts an opposing force. Along

http://www.rqriley.com/suspensn.html (7 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension with its primary function of reducing body-roll, the anti-roll bar will also reduce the combined cornering force and the adhesion limits of the side-by-side tires that are being acted upon. Consequently, the location and stiffness of the bar can be modified to influence the oversteering or understeering characteristics of the vehicle.

An oversteering tendency will be reduced by locating the anti-roll bar at the front where it will reduce the cornering force and adhesion of the front tires. If the vehicle understeers, the anti-roll bar should be located at the rear. If an anti-roll bar is already required at both ends of the vehicle to achieve adequate roll stiffness, use an anti-roll bar of greater stiffness/diameter at the end of the vehicle where reduced cornering force is desired, and use a less-stiff/smaller-diameter bar at the other end.

Changing the tire's inflation pressure has a more limited effect on handling characteristics. Inflation pressure influences the slip angle of the tire. A softer tire will require a greater slip angle in order to achieve equal cornering forces. Also a lower inflation pressure will cause the tire to reach its limit of adhesion at lower g-loads. Consequently, increase the inflation pressure at the end of the vehicle requiring greater cornering forces (greater adhesion). Reduce the inflation pressure for reduced adhesion and cornering forces.

Tire/wheel size is another important variable. Larger diameter tires tend to ride more smoothly, and they also develop greater cornering forces. However, installing larger tire to improve cornering is not always practical. Larger tires can cause clearance problems if the vehicle was not design for them, and they also affect suspension geometry. An alternative approach would be to install the same tires on wider rims. This provides a wider cross-sectional base for the tires and thereby improves cornering. Wider tires also aid in cornering, but at the expense of a rougher ride. Tires with a lower aspect ratio (low profile tires) develop significantly greater cornering forces and therefore can be used to improve the handling of a vehicle with marginal handling characteristics. Within limits, varying tire-size, rim- width and inflation-pressure can adjust cornering forces to achieve the desired overall performance.

The Effect of Polar Moment of Inertia

The moment of inertia has to do with a body's resistance to angular acceleration. Polar refers to the ends. Consequently, the polar moment of inertia of a vehicle is related to the mass that is located near the front and rear. The effect of polar mass can be experienced by rotating a dumbbell back-and-forth around a central axis. The weight concentrated at the ends makes the barbell resist changes in direction. A ball of equal weight will reverse directions with little effort because the mass is concentrated at the center. Most passenger cars are designed with a relatively high polar moment of inertia. The engine is located over the front or rear axle and the fuel and luggage are located at the opposite end. The center of the vehicle is hollow to provide room for the occupants.

A low polar moment of inertia results in a vehicle with more responsive handling, but it also produces a more choppy ride. A vehicle with high polar mass is less nimble, but it offers a smoother ride. Sports cars tend to have a low polar moment of inertia for nimble handling, and they also tend to ride more roughly than passenger cars. Normally, a good balance between ride and handling can be http://www.rqriley.com/suspensn.html (8 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension achieved. The designer does not have to decide between one or the other extreme.

Rollover Threshold

At the most fundamental level, a vehicle's rollover threshold is established by the simple relationship between the height of the center of gravity and the maximum lateral forces capable of being transferred by the tires. Modern tires can develop a friction coefficient as high as 0.8, which means that the vehicle can negotiate turns that produce lateral forces equal to 80 percent of its own weight (0.8 g) before the tires loose adhesion. The cg height in relation to the effective half-tread of the vehicle determines the L/H ratio which establishes the lateral force required to overturn the vehicle. As long as the side-force capability of the tires is less than the side-force required for overturn, the vehicle will slide before it overturns. This analysis is useful for comparing the rollover propensity of various vehicles, as shown in Table T-1. Under dynamic conditions, however, a vehicle's rollover threshold is a more complicated issue.

Table T-1

ROLLOVER THRESHOLD COMPARISON

Vehicle Type cg Height (inches) Tread (inches) Rollover Threshold (lateral g-load)

Sports Car 18-20 50-60 1.2-1.7

Compact Car 20-23 50-60 1.1-1.5

Luxury Car 20-24 60-65 1.2-1.6

Pickup Truck 30-35 65-70 0.9-1.1

Passenger Van 30-40 65-70 0.8-1.1

Medium Truck 45-55 65-75 0.6-0.8

Heavy Truck 60-85 70-72 0.4-0.6

Rapid onset turns impart a roll acceleration to the body that can cause the body to overshoot its steady- state roll angle. This happens with sudden steering inputs, it occurs when a skidding vehicle suddenly regains traction and begins to turn again, and it occurs when a hard turn in one direction is followed by an equally hard turn in the opposite direction (slalom turns). The vehicle's roll moment depends on the vertical displacement of the center of gravity above its roll center. The degree of roll overshoot depends upon the balance between the roll moment of inertia and the roll damping characteristics of the suspension. An automobile with 50 percent (of critical) damping has a rollover threshold that is nearly one third greater than the same vehicle with zero damping. http://www.rqriley.com/suspensn.html (9 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension

Overshooting the steady-state roll angle can lift the inside wheels off the ground, even though the vehicle has a high static margin of safety against rollover. Once lift-off occurs, the vehicle's resistance to rollover rapidly diminishes, which results in a condition that quickly becomes irretrievable. The roll moment of inertia reaches much greater values during slalom turns wherein the forces of suspension rebound and the opposing turn combine to throw the body laterally through its roll limits from one extreme to the other. The inertial forces involved in overshooting the steady-state roll angle can exceed those produced by the turn-rate itself.

Tripping is another cause of rollover in an otherwise rollover-resistant vehicle. Tripping occurs when a vehicle skids against an obstacle, such as a curb. In this case, the lateral speed of the vehicle is suddenly arrested and extremely high momentary loads are imposed across the vehicle's center of gravity. If the load spike exceeds the vehicle's rollover threshold, rollover will occur.

Figure 4: Rollover Caused by Tripping (9k)

The nature of these conditions and the resulting forces are difficult to predict in real-world conditions. Consequently, the best design for rollover protection will include adequate roll damping and the greatest possible static margin of safety against rollover.

The Relationships of Steering Axis Inclination, Caster, Camber, and Pivot Radius In Front Suspension Systems

The geometric relationships of the front wheels would be relatively simple if it were not for the fact that they also steer the vehicle. Once the wheels take on the job of steering, the dynamic requirements and the angular relationships become much more complicated. With early beam axles, the steering movements were provided by the kingpin. The first kingpins were aligned perpendicular to the ground and as a result, steering movements were very simple; a wheel steered around its axis just like a door swings on a hinge. However, a suspension with a perpendicular kingpin has no self-aligning characteristics, and the slightest bump at one wheel can impart significant steering inputs. Consequently, the perpendicular kingpin was discarded very early on. Thereafter, the kingpin was attached to the axle at an angle so the swivel line projected outboard and forward toward the ground plane. The lateral tilt is known as the steering axis inclination and the longitudinal tilt is called the caster angle.

Steering Axis Inclination

Steering axis inclination refers to the lateral tilt of the axis around which the wheel rotates when it is steered. By leaning the steering axis inboard at the top (or outboard at the bottom) the swivel-line is projected much nearer the tire centerline at ground level. That reduces directional disturbances caused when the tire encounters an obstacle. If the steering axis meets the ground inboard of the tire centerline, an obstacle will cause the wheel to steer outboard. If the steering axis projects outboard

http://www.rqriley.com/suspensn.html (10 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension past the tire centerline, an obstacle will create a steering input toward the inside. A steering axis that meets the ground at the tire centerline eliminates the steering inputs of obstacles, but it also eliminates the "feel" of the road.

The distance the steering axis is offset from the tire centerline is called the "pivot radius". Cars are normally designed with a positive pivot radius (the tire centerline is outboard of the swivel-line at ground level) in order to provide a feel of the road. However, if the pivot radius is too great, obstacles can then produce uncomfortable steering inputs that, in the extreme, can cause loss of control.

Figure 5: Pivot Radius (5k)

Other requirements of the suspension system, as well as mechanical conflicts between components, may prevent the designer from locating the steering axis projection appropriately close to the tire centerline. Wheels can then be set at a slight positive camber angle to move the contact patch inboard toward the swivel line.

Steering axis inclination is responsible for most of the self-centering force of the steering system. The steering axis of passengers cars normally leans inboard 10 to 15 degrees. The incline places the swivel- line the wheels off-plane with the ground. As a result, a steering movement in either direction moves the wheels downward and lifts the vehicle upward. The weight of the vehicle therefore produces a resultant that keeps wheels aligned to the vehicle heading.

Figure 6: Effects of Steering Axis Inclination (5k)

Caster Angle

Caster angle introduces a new element. The caster angle refers to the longitudinal inclination of the steering axis. It creates a self-centering force that is somewhat different from the one created by the lateral steering axis inclination. A positive caster is established when the steering axis meets the ground ahead of the center point of the contact patch (a point directly under the axle). Most passenger cars have a positive caster on the order of 0 to 5 degrees. A positive caster causes the wheel to trail behind the steering axis. When the vehicle is steered, the caster angle develops an opposing force that tends to steer the vehicle out of the turn. Click on Figure 7 to retrieve a drawing of caster angle.

Figure 7: Caster Angle (5k)

Another effect of caster angle is that it causes the camber angle to change when the wheels are steered. When the vehicle is steered, the inside wheel progresses into a positive camber and the outside wheel progresses into a negative camber. Considered independently of steering axis inclination, the effect of caster in a turn is to drop the side of the vehicle on the outside of the turn and to raise it on the inside of the turn.

http://www.rqriley.com/suspensn.html (11 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension Camber Effects

Camber is the lateral inclination of the wheel. If the wheel leans out at the top, away from the vehicle, it has a positive camber angle. With a negative camber angle, the wheel leans inward at the top. Camber-changes occur when the body leans during a turn and when the wheels move vertically through jounce and rebound. A wheel set at a camber angle produces "camber thrust," which is a lateral force generated in the direction of the lean. The magnitude of camber thrust is substantially less than the forces generated by slip angle (direction in which the tire is rolling). Bias ply tires produce significantly greater camber thrust than do radial tires.

Figure 8: Camber Thrust (5k)

As a general rule, the vehicle will handle well if the camber angle meets certain criteria. At the fully laden ride height, the front wheels should assume a zero or slightly positive camber angle. During jounce, as the wheel moves upward through its arc, camber should progress to a negative angle in relation to the vehicle. The purpose of the negative camber angle is to maximize cornering forces by keeping the outside tire upright or at a slightly negative camber angle as the body leans to the outside of the turn. The second purpose of negative camber is to minimize lateral movement, or tire scrubbing, at the contact patch.

When wheels move through the arc prescribed by the suspension linkages, they may be dragged laterally inboard and outboard as they move up and down. Lateral movement causes a scrubbing action at the contact patch, which reduces adhesion and shortens tire life. Severe lateral scrubbing can also cause a condition known as "bump-steer." A suspension system with a large scrubbing action will cause the vehicle to veer to one side when adhesion or vertical wheel movement is not equal at both side-by-side wheels. Ideally, the camber angle will change during jounce enough to compensate for the suspension-induced lateral movement at the hub. Camber change should also compensate for body roll to keep the outside wheel from lean away from the turn. Tire scrubbing (changes in the tread) should be minimized by good suspension design, and camber changes should be minimal as well.

Figure 9: Wheel Movements During Bounce (6k)

Consideration of camber angle has traditionally emphasized the front wheels. With the proliferation of independent rear suspension systems, the effects of camber angle have become just as important at the rear of the vehicle. Rear wheel camber changes can augment cornering forces, and they can influence the balance between oversteer and understeer.

Steering Geometry

The idea of steering the front wheels around separate axes was invented in 1817 by a Munich carriage builder named Lankensperger. His agent, a fellow by the name of Rudolph Ackerman, took out an English patent on the invention. Later in 1878, a French carriage builder, Charles Jeantaud, introduced http://www.rqriley.com/suspensn.html (12 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension a refinement known as the "Jeantaud Diagram" which provided a more precise prediction of the correct geometry. Today, Lankensperger's invention, along with Jeantaud's refinements, is usually referred to as "Ackerman Steering."

An important requirement for wheels steered around separate axes is that the inside front wheel must turn at a sharper angle than the outside wheel. This is due to the fact that the inside wheel moves through a smaller arc. The difference between the inside and outside steering angles progressively increases as the wheels are turned more sharply (higher lock angles). At the low steering angles typical of highway speeds, differential steering is relatively unimportant. Figure 10 illustrates the geometry of Ackerman Steering.

Figure 10: Ackerman Steering (5k)

Books on chassis design explore the subject in great detail and provide the graphical and analytical data required to determine length and inclination of steering knuckles, both ahead of and behind the wheels. Calculations can be quite involved and must take into account a host of variables in linkage and suspension system layouts. Several years ago, Walter Korff worked out a table that applies to simple beam axles with the steering knuckles behind the kingpin axes. Since the results of most calculations must be graphically verified, one could use Mr. Korff's table as a starting point, then adjust the angles to remove real-world errors.

Table T-2

STEERING KNUCKLE ANGLE (Retrieve Figure 10 for Angle X illustration)

Wheelbase Tread Wheelbase Tread Angle X Angle X (inches) (inches) (inches) (inches)

100 42.5 100 60 90 38 90 54 72 degrees 66 degrees 80 34 80 48 70 30 70 42

100 45 100 62.5 90 40.5 90 56 71 degrees 65 degrees 80 36 80 50 70 31.5 70 44

http://www.rqriley.com/suspensn.html (13 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension

100 48 100 64 90 43 90 57.5 70 degrees 64 degrees 80 38.5 80 51 70 33.5 70 45

With independent suspension systems, each front wheel is steered individually by a separate link. This arrangement introduces important new geometric relationships. The links of a simple rack and pinion steering assembly must be of the correct length and correctly located. If the geometric relationships are not correct, bumps can produce steering inputs. In general, the steering linkage should be located near, and parallel with, the lower suspension link, as shown in Figure 11. The rate of differential steering is affected by the for-to-aft location of the steering box in relation to the steering knuckles, as well as by the steering knuckle angular offset.

Figure 11: Steering Link Relationship(5k)

Front Suspension Systems

The two types of front suspension systems that account for nearly all vehicles in production today are the double A-arm and the MacPherson strut. There are also a few variations that have not worked well in large-car applications, but may offer new possibilities with low mass vehicles.

Beam Axle

The beam axle is a familiar design but it is no longer considered appropriate for automobile application. It is strong and inexpensive, and as a result, it is ideally suited to heavy trucks and smaller utility vehicles. The advantages of the design include its simplicity, low cost, and rugged layout, as well as a naturally high roll center which reduces body roll in turns. The disadvantages have to do with its performance. A bump at one wheel is transferred across to the other wheel. In addition, the gyroscopic forces of both wheels work together to induce shimmy, and the design results in greater unsprung weight and a rough ride.

The Double A-Arm Suspension System

The upper and lower A-arm suspension has been the predominate system of U.S. cars for nearly half a century. Early versions had two parallel A-arms of equal length which resulted in wheels that leaned outboard in turns. The design also caused excessive tire scrubbing because of the large variation in tread-width as the wheel moved off the neural position. When the concept of unequal length A-arms was developed, designers were given a new design tool that provided almost infinite control over the movements of the wheels. Today, handling characteristics are limited only by the limits of tire performance and the basic weight and balance of the vehicle, not by the mechanical limitations of the suspension system.

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The unequal length, non-parallel A-arm system allows the designer to place the reaction point of the wheel at virtually any point in space. The actual position of that point (virtual reaction point) is controlled simply by moving the inboard connection of the upper and lower A-arms up or down, or closer together or farther apart. For example, moving the inboard connection points farther apart moves the reaction point farther way until it reaches infinity when the arms are parallel. If the inboard connection points are moved still farther apart, the reaction point then flips to the other side and assumes a position in space some distant to the outside of the wheel.

A line projected from the bottom of the wheel to the virtual reaction point establishes the vehicle roll center at the point of intersection with the vertical centerline of the vehicle. The height of the roll center is therefore controlled by varying the inboard connection points of the upper and lower A-arms as needed to vary the height of the virtual reaction point (see Figure 12).

Figure 12: Upper and Lower A-Arm Suspension (6k)

Anti-dive is another feature that is easily designed into the double A-arm suspension. Vehicles with a soft ride tend to dive when braking. This is due to the weight transfer toward the front of the vehicle. The tendency to dive on braking can be partially alleviated by tilting the upper A-arm as shown in the drawing in Figure 13.

Figure 13: Anti-Dive Design (5k)

The MacPherson Strut

The MacPherson strut front suspension system was invented in the 1940's by Earl S. MacPherson of the Ford Motor Company. It was introduced on the 1950 English Ford and has since become one of the predominate suspensions systems of the world. This simple system utilizes the piston rod of the built-in telescopic shock absorber to also serve as the kingpin axis. Normally, a coil spring is mounted over the strut assembly, in which case, a thrust bearing at the top of the spring prevents spring wind- up during turns. The lower link may be in the form of an ordinary A-arm. More commonly, a narrow transverse link (sometimes called a track rod) locates the lower end of the strut in the transverse direction and a separate member called a radius rod locates the assembly in the longitudinal direction. However, the anti-roll bar can serve as the longitudinal link and thereby eliminate the separate radius rod.

The advantages of the MacPherson strut include its simple design of fewer components, widely spaced anchor points that reduce loads, and efficient packaging. From a designer's viewpoint, its disadvantages include a relatively high overall height which tends encourage a higher hood and fender line, and its relatively limited camber change during jounce. A disadvantage on the consumer level is the comparatively high cost of servicing the shock absorber.

A small camber change during jounce and rebound is characteristic of the strut design. The vehicle http://www.rqriley.com/suspensn.html (15 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension roll center is controlled by raising or lowering the inboard anchor point of the transverse link, and by varying the steering axis inclination.

Figure 14: The MacPherson Strut (4k)

Both Urbacar and Urba Electric utilized a specially designed miniature MacPherson that did not suffer as badly from the tall shock-tower syndrome of existing designs. Another interesting concept utilizes a flat spring as the transverse link. The idea of replacing a suspension link with a leaf spring has been tried in a variety of configurations. Difficulties have centered on the high longitudinal loads imposed caused by braking, and the limited deflection characteristics typical of leaf springs. However, the lower loads typical of low mass vehicles, along with the greater control over spring characteristics provided by composite spring designs, offer an opportunity for a new look at unconventional suspension systems.

Figure 15: Modified MacPherson for Three Wheel Car (7k)

Rear Suspension Systems

Designers have traditionally invested a great deal of effort in front suspension design. Often, the rear axle was simply hung in place and the driving was left to the front. Things have changed in the last couple of decades. Rear suspension design has become just as sophisticated as the front. In fact, the design variations are probably greater at the rear. Rear suspension systems can be divided into three basic categories:

● Dead Axles, such as the one-piece beams at the rear of front-wheel-drive vehicles ● Live axles with the final drive incorporated. ● Independent suspension systems.

Dead Rear Axle

The dead rear axle comes in a variety of configurations. Every layout of the powered rear suspension system becomes a dead axle layout when power is not transferred to the wheels. The rear wheels are not considered as steering wheels. As a result, even the beam axle is a more docile layout when the axle is used at the rear in an unpowered configuration. The most popular dead rear axles include the beam axle and the trailing arm and semi-trailing arm suspensions.

One-Piece Live Axle

The live rear axle is similar to the beam front axle or the dead rear axle, except that it is subjected to the torsional loads involved in transmitting power to the road. The design is rugged, simple, and relatively inexpensive, but its high unsprung weight results in a poor ride. The rear axle is not involved in steering so the disadvantages are somewhat less troublesome than those experienced with http://www.rqriley.com/suspensn.html (16 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension the beam front axle. However, unsprung weight is very high and as a result the design produces a rougher ride and is very susceptible to wheel hop and tramp.

The traditional live axle of older American cars is the Hotchkiss drive. The Hotchkiss drive is distinguished by its semi-elliptical leaf springs that also serve as the suspension links. Difficulties with the Hotchkiss drive have to do with its limited ability to transfer torque, its high interleaf friction and high unsprung weight, and the imprecise location of the rear axle assembly. Consequently, it is difficult to achieve a good ride and to appropriately manage the torsional loads of braking and power transfer. Braking and acceleration transfer high torsional loads to the axle, which can rotate off plane due to the flexibility of the springs.

Figure 16: Hotchkiss Rear Axle (4k)

Designers have attempted to overcome the limitations of the live axle by replacing the leaf springs with coil springs and locating the axle with linkages of various configurations. Such systems do improve cornering performance, as well as smooth out the ride. When linkages are introduced, control is also gained over the dive and squat characteristics associated with acceleration and braking.

The Swing Axle

Ride and handling are greatly improved when the wheels can respond independently to disturbances. The swing axle design is the most simple way of achieving an independent rear suspension. Its simple design utilizing the drive axle as the transverse link and the inboard universal joints as the suspension axis was responsible for its early attractiveness. With swing axles a disturbance on one side is not transferred to the opposite wheel as it is with a solid axle. Ride and handling are therefore improved. The first swing-axle design to gain wide popularity in the U.S. was the immortal VW Beetle. When the Beetle was introduced into the U.S., its fully independent suspension system represented a significant step forward in suspension design. However, swing axles do suffer from characteristic limitations and as a result the design is rarely used on modern cars.

Swing-axles produce large changes in camber and tread during bounce, and the design can become unstable in turns due to the "jacking" effect. Setting the wheels at a negative camber can reduce the tendency to jack. However, too much negative camber can also produce a vehicle with a vague, mushy feel of directional instability. Slings under the axles or zee brackets can be designed to limit downward travel and thereby avoid wheel tuck-under. A correctly designed swing axle suspension works reasonably well, but its undesirable characteristics can never be fully overcome.

Figure 17: Swing-Axle Rear Suspension (9k)

Trailing Arm and Semi-Trailing Arm Suspensions

With trailing arm and semi-trailing arm suspensions the wheels are free to bounce independently.

http://www.rqriley.com/suspensn.html (17 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension Each wheel moves up and down around the axis of a trailing or semi-trailing arm. The difference between the two designs is that the axis of the trailing arm is at right angles to the vehicle centerline whereas the semi-trailing arm axis angle inboard and toward the rear. Both configurations are popular for either powered or non-powered rear suspension systems.

If the rear wheels are powered, the final drive is mounted in a fixed location and each wheel is driven by an axle half-shaft. Each half-shaft is equipped with an outboard and inboard universal joint to accommodate angular variations during bounce. Half-shafts also have a telescopic action to accommodate the variation in final drive-to-wheel distance as wheels move up and down. Rear end lift during braking is countered by the downward component at the leading end of the arms.

Body roll produces camber and toe changes in the semi-trailing arm design. Consequently, camber thrust and modest slip-angle forces can combine to produce steering inputs as the body rolls to the outside of the turn. Roll-steer effects are at a minimum when the arm axis is parallel to the ground and increase when the inboard end is raised or the outboard end is lowered. The degree of camber change depend primarily on the distance to the instantaneous center. The instantaneous center is normally located no closer than the centerline of the opposite wheel. A closer location will produce wheel movements that emulate the swing-axle, along with the negative attributes of tuck-under and unfavorably large camber change.

Figure 18: Trailing Arm and Semi-Trailing Arm Rear Suspension (9k)

Strut and A-arm Rear Suspensions

The rear suspension system can emulate the design of the MacPherson strut or the upper and lower A- arm front suspension system. At the rear, a MacPherson style suspension is referred to as a "Chapman strut", or simply a "strut" suspension. The geometry, mechanical layout, and wheel travel characteristics are essentially the same, except the strut rear suspension does not steer (at least in the traditional sense). Upper and lower A-arm systems come in a variety of unique configurations. Designs sometimes utilize the drive axles as suspension links, such as with the Jaguar and Corvette rear suspension systems.

Suspension Guidelines for Extremely Low Mass Vehicles

Extremely low mass vehicles are often penalized by poor suspension design. Just the opposite approach is necessary in order to bring out the natural handling capabilities of a low mass vehicle. Whereas a high mass vehicle has greater inherent stability, a low mass vehicle has greater inherent agility and handling precision. These natural characteristics can be degraded by poor design, or they can be enhanced by good design. Use the following general guidelines with low mass vehicles.

● Use the fully-laden weight for performance and handling calculations. ● Keep unsprung weight to a minimum. Consider a simplified suspension design, and use

http://www.rqriley.com/suspensn.html (18 of 19) [9/6/2002 08:02:09] Automobile Ride, Handling, and Suspension lightweight alloys or plastic composites for springs and structural members. ● Keep the center of gravity as low as possible. Correct cg location is especially important in low mass vehicles, and even more so in three wheel designs. ● The center of gravity should be ahead of the wheelbase mid-point of a four wheel platform, and no farther than 35 percent of the wheelbase from the side-by-side wheels of a three wheeler. ● The tread should be as wide as possible and the wheelbase as long as possible within the constraints of the vehicle package. Locate wheels at each of the extreme corners of the vehicle. ● Use a fully independent suspension, and keep the contact patch location stable (minimal lateral movement). ● Eliminate suspension and steering geometry errors. Go the extra mile for precession. ● Establish the roll center according to the vehicle cg. If the cg is extremely low, the roll center may be at, or near ground level. The roll moment should be lower for extremely low mass vehicles. ● Roll stiffness is essential for a low mass vehicles. If the vehicle understeers, place the anti-roll bar at the rear. If it oversteers, place the anti-roll bar at the front. ● For increased traction, use wider rims and/or wider tires. ● A torsionally rigid platform (frame) is essential for precise handling characteristics. ● At freeway speeds, aerodynamic effects will be an important consideration, and aerodynamic effects increase as weight decreases. Consequently, the aerodynamic center of pressure should be as close as possible to the vehicle center of gravity. Eliminate lift, keep ground clearance minimal, angle the body slightly downward at the front.

More Information

● Three-Wheelers in Automotive Application.

● Mr. Riley's Book: Alternative Cars in the 21st Century: A New Personal Transportation Paradigm

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Robert Q. Riley Enterprises is a full service product design and development consultancy. Robert Q. Riley, the firm's founder and President, is an industrial designer and mechanical engineer with over 20 years experience in all phases of product design, development, and commercialization. Satisfied clients include corporate clients such as 3M Company and B. Braun Medical Industries, development firms such as Transit Innovations, and individual inventors and entrepreneurs. Our new product development strategy centers on efficient use of resources and an enterprising approach to development tasks. Our excellence comes from years of experience with start-up operations where innovative solutions and efficiency with human and financial resources is essential.

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Welcome to the DIY corner of our website where you'll find some of the world's most Click Image for Info exciting projects that you can build from plans. Our projects are designed to the highest quality standards. Most of our plans were first distributed exclusively by either Popular Mechanics, Mechanix Illustrated, or Home Mechanix magazine, and nearly 500,000 are in the hands of satisfied enthusiasts around the world. Click on an image in the left margin for more information about a project. You can place your order online using a credit card, or order by fax, phone, or mail using the order form at the bottom of this page. Click on the Guaranteed Badge for details about our quick shipment and money-back guarantee.

Scientific

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Gluhareff Pressure Jet Engine is a fully throttleable jet engine available in 20-lb, 40-lb, 80-lb, and 130-lb thrust sizes. Plans include technical and engineering details, step-by-step assembly instructions, and construction drawings. Price: Standard Plans Package - $75; Deluxe Plans Package - $150. Click on the image for more information and details on the contents of jet engine plan sets. Order Jet Engine Plans.

Cars, Three-Wheelers, EVs & Hybrid

Tri-Magnum is a high-performance three-wheel sports car. It was introduced in Mechanix Illustrated magazine, and today, it's our most popular design. Plans include 13 large drawings and a photo-illustrated book. Price: $95. Order Tri-Magnum Plans.

Doran is the result of six years of development and testing. Build this high-performance three wheel sports car for either gasoline or electric power. Scale drawings and instructions are bound together in the 8-1/2 x 11 inch construction manual. Price: $49. Order Doran Plans.

Centurion achieves 128-mpg fuel economy on its diesel engine. It appeared in Mechanix Illustrated magazine and in the movie Total Recall. Plans include 13 large drawings and a photo-illustrated book. Price: $95. Order Centurion Plans.

Trimuter is a record-holder with over 30,000 plans distributed. It accepts either battery-electric or ICE power. It appeared in Mechanix Illustrated magazine and in the movie Total Recall. Plans include 12 large drawings and a photo-illustrated book. Price: $95. Order Trimuter Plans.

Town Car is a series hybrid-electric vehicle. It appeared in Mechanix Illustrated magazine and in the movie Total Recall. This new edition of the plans includes 12 drawings and a large photo-illustrated book. Price: $95. Order Town Car Plans.

Urba Electric was the test bed for proving out the CVT speed control system for EVs. It was featured in Mechanix Illustrated magazine. Plans include 14 http://www.rqriley.com/plans.html (2 of 7) [9/6/2002 08:03:13] Plans for building cars, vans, three-wheelers, hovercraft, EVs, hybrids, boats, subs and more

large drawings and a booklet. Price of plans: $75. Order Urba Electric Plans.

UrbaCar tops 60 mph and delivers 55 mpg fuel economy. It was featured in Mechanix Illustrated magazine. Plans include 10 large drawings and a booklet; available in both CAD and printed formats. CAD Plans - $75; Printed plans - $95; both formats - $150. Order UrbaCar

UrbaTrike cruises at 55 mph and runs 50 miles on its eight 6-volt golf car batteries. It was featured in Mechanix Illustrated magazine. Plans include 10 large drawings and a 22-page booklet. Price: $65. Order Urba Trike Plans.

Vans - Campers

Phoenix expands tent-trailer style into a large camper. It was featured in Popular Mechanics and Mechanix Illustrated magazines. It also appeared in the movie Total Recall. Plans include 11 large drawings and a photo-illustrated booklet. Price: $85. Order Phoenix Van Plans.

Boonie Bug is a VW-van-based minivan. It was featured in Popular Mechanics magazine, and it appeared in the movie Total Recall. Plans include nine large drawings and a booklet. Price of plans: $65. Order Boonie Bug Plans.

MiniHome is built on a VW Bug chassis and has compact motorhome-style facilities for four. It was featured in Mechanix Illustrated magazine. Plans include ten large drawings and a 17-page booklet. Price: $55. Order MiniHome Plans.

Budget Camper fits long-bed American pickups. It was featured in Mechanix Illustrated magazine. Plans include seven large drawings and a 12- page booklet. Price of plans: $45. Order Budget Camper Plans.

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Ground Hugger XR2 carbon fiber recumbent bicycle is our latest design. A landslide of orders made it our most popular project, even before plans were released. It's also the winner of the 2001 Australian World Solar Cycle Challenge (B-Class). Plans include five large drawings and a full- size 34 x 60 inch template sheet, plus a 60-page construction manual. Price: Standard Package - $75. Deluxe Package (with CD-ROM) - $100. Order Ground Hugger XR2 Plans

Ground Hugger is the design on which the new XR2 is based. It is one of the most thoroughly proven recumbent designs around. It was featured in Popular Mechanics magazine. Plans are available on CAD in electronic format, and as printed drawings. Plans include four large drawings and a 12-page booklet. Price: CAD - $35; printed - $39; both CAD and printed - $55. Order Ground Hugger Plans. Hovercraft

Pegasus is a hovercraft for youngsters designed as an educational father/son project. It was featured in Popular Mechanics magazine. Plans include six large drawings and a 32-page, photo-illustrated book with hovercraft principles of operation. Price: $35. Order Pegasus Plans.

Tri-Flyer is a three-place, high-performance hovercraft that can top 80 mph. Plans include seven large drawings and a 60-page, photo-illustrated book with hovercraft principles of operation. It was featured in Popular Mechanics magazine. Price of plans: $45. Order Tri-Flyer Plans.

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HydroRunner is a high-performance personal watercraft using an outboard engine. It was featured in Popular Mechanics magazine. Plans include six large drawings and a 36-page, photo-illustrated book. Price of plans: $39 Order HydroRunner Plans.

AquaSub is a one-man sports submarine that operates in the near-surface environment. The interior is dry, so no scuba gear is needed. It was featured in Mechanix Illustrated magazine. Plans include 10 large drawings and a booklet describing step-by-step how to build it. Price of plans: $45. Order AquaSub Plans

Surf Sailer is a combination sailboat, motor boat, paddle board, and surfboard. It was first used as a life-saving device on the beaches of Israel. Later, Popular Mechanics magazine featured the plans-built version. Plans include six large drawings and a 14-page booklet. Price of plans: $39. Order Surf Sailer Plans.

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Super Spa can be built either fully in-ground or above ground. Plans give complete instructions for building a custom designed deck and spa. Featured in Home Mechanix magazine. Plans include four large drawings and a 34-page, photo-illustrated book. Price of plans: $35. Order Super Spa Plans.

Old Hickory smoke cooker imparts old fashioned smoke-cooked flavors to food, and it almost cooks by itself. Plans include two large drawings and a photo- illustrated booklet showing step-by-step how to build it. Price of plans: $19. Order Old Hickory Plans.

Books

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Alternative Cars in the 21st Century: A New Personal Transportation Paradigm, by Robert Q. Riley (Society of Automotive Engineers, 1994): A review of transportation's role in the world's energy and environmental problems, along with a technology review of alternative transportation options. Heavily illustrated with graphs, tables, and photos of alternative cars designs, both actual and proposed. Hardbound, 396 pages. Price: 39.00. Order Book

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Plans are in AutoCAD's DWF format. Download the free WHIP! plug-in to view, pan, zoom, and print the drawings from within your web browser. Mini-Flyer is a simple-to-build hovercraft powered by a leaf blower. You can build this fun and educational project in less than a day. Plans include 2-D CAD drawings and a 3-D model.

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http://www.rqriley.com/download.html (1 of 3) [9/6/2002 08:03:23] Free Plans, Software and Information

Hovercraft Lift Calculator: Calculates airflow, power, platform pressure, fan diameter, number of blades, and more. Rhinoceros 3-D NURBS modeler for Windows. Your free copy of Rhino works indefinately to view, pan, rotate, zoom, and render 3-D models. Only the "save" function becomes dissabled on expiration. Requires Pentium processor, 32 MB ram, and 15 MB disk space. Runs under Windows 95, 98, and NT. Click here for more info.

3-D Models of Our DIY Projects: View models using the Rhino demo (see above), or import them into other 3-D programs. Click link to see available models. Free background images of your favorite project for your Windows desktop. Clicking on the link takes you to a download page with thumbnails of available desktop images. Each image is available in three different resolutions to fit the most common monitor settings.

Get a copy of WinZip to compress files so they take up less disk space, and unpack compressed files downloaded here. For Windows only. Click the image to install Autodesk's WHIP! plug-in. WHIP! lets you view, pan, zoom, and print DWF CAD drawings from within your web browser. After installing WHIP! and loading a drawing, right-click anywhere on the drawing to display the navigation menu. Requires Netscape 4.05 or later, or MS Internet Explorer 4.01 or later running under Windows 95, 98 or NT 4.0.

How-To Information

● One-Off Construction Using Fiberglass Over Urethane Foam is a hands-on, photo- illustrated review of how it's done. ● Licensing and Insuring Homebuilt Vehicles explains how to be sure your creation meets regulations, and how to get it insured. ● How to Develop, Protect, and Market New Product Ideas is a must-read for inventors and entrepreneurs. ● How to Develop New Products describes the organization and flow of activities in a new product development project. ● Lean Machine: A Case Study of the Evolution of a Design takes you step by step though the development of a home gym system.

Technical Papers

http://www.rqriley.com/download.html (2 of 3) [9/6/2002 08:03:23] Free Plans, Software and Information

● Different Roads: Personal Mobility in the 21st Century is a comprehensive presentation on design options for future personal mobility. ● Automobile Design: Year 2010 and Beyond reviews likely directions in future car design. ● Three Wheel Cars: The Factors That Determine Handling and Rollover Characteristics

● Automobile Ride, Handling, and Suspension Design provides an overview of suspension systems and the factors that determine ride and handling. ● Electric and Hybrid Vehicles: The Benefits, Challenges, and Technologies reviews EV technologies and design practices. ● Transportation's Impact on Energy and the Environment looks at the world's energy and environmental problems, and possible solutions. ● The Role of Appearance Models and Mockups: A Case Study of the ARRIS Design explains the value of appearance models in product design. ● The Power of Design. Visionary design alone can create new products, new appeals, and new markets.

http://www.rqriley.com/download.html (3 of 3) [9/6/2002 08:03:23] Become an Affiliate or a Vendor and make extra profits.

Join Our Affiliate or Vendor Program

Link to This Site and Receive Commissions or... We Sell Your Product

If you have a related website, or you have build-it- yourself plans or related products, you can make extra profits by participating in one of our programs.

Click Image for Details Affiliate Program Link to This Site and Make Commissions

Install a link to this site and make commissions on sales from your link. Here Click Link for... are the highlights:

Getting Started ● You put a banner on your site and make comissions on sales. Sample Report ● Your customers click through to a special gateway page that directs them Agreement to the build-it-yourself plans area. Application Form ● You make comissions even if your customer purchases at a later date.

This program will To become an affiliate, review the Affiliate Program Agreement, then fill out the become active in Application Form (see links to left). Once your application is approved, you will January 2002. be contacted with details on how to install the link and track your sales.

Vendor Program We Sell Your Product

http://www.rqriley.com/partners.html (1 of 2) [9/6/2002 08:03:26] Become an Affiliate or a Vendor and make extra profits.

Click Link for... There are two ways to become a vendor:

Instructions & Rules ● We sell your plans or related products, or.... Agreement ● We prepare plans, then publish and sell plans to your project. Application Form To submit your product(s), review the Vendor Program Instructions & Rules and This program will the Agreement, then fill out the Application Form and submit your product. You become active in will be contacted after your application has been reviewed. January 2002.

Retail CD-ROMs Distributors & Retailers

Do-it-yourself goes high-tech with this brand new line of interactive CD-ROMs. Click Link for... Simple to use CD-ROMs elevate do-it-yourself to the level of professional design studios. Includes 2-D and 3-D CAD files, and built-in utilities for CD-ROM Info viewing, panning, rotating, rendering, printing, and measuring 3-D CAD models on an ordinary PC. Click on CD-ROM Info to the left for more details.

http://www.rqriley.com/partners.html (2 of 2) [9/6/2002 08:03:26] Robert Q. Riley Enterprises Information for the Press

Press Room

Background Information, Technical Papers, and CMYK Images for the Press

Welcome to the Press Room. Check here for CMYK images, news releases, technical information, quotes, and the latest developments at Robert Q. Riley Enterprises.

News Releases

Build-It-Yourself Goes High-Tech. Advanced 3-D CAD technology for build-it-yourselfers in a new line of plans-built February 07, 2000 projects on CD-ROM. Featured in the March 2000 issue of Wired magazine. Supplemental on-line information.

Release Archives

CMYK Images for the Media

http://www.rqriley.com/press.html (1 of 4) [9/6/2002 08:03:38] Robert Q. Riley Enterprises Information for the Press

To download images NOW, fill out form and press "Submit." Click image for larger preview

Image Download Form Name: Firm: 4.4 x 2.9 x 300ppi 5 x 3.3 x 300 ppi E-mail:

Phone: For use in (prospective feature/story):

5.4 x 4 x 300 ppi Press "Submit" to go to the download page. 2.4 x 2.8 x 300ppi

Additional Images Available on Request (media only) Image files vary in size from 0.5 to 2.5 MB Click image for larger preview Image Request Form Check desired images

Name: AquaSub 1 AquaSub 2 Town Car 1 Firm: E-mail: Phone: For use in (prospective feature/story):

Trimuter 1 HydroRunner 1 Pegasus

Press "Submit" to send your request. Selected images will be sent via e-mail. IMPORTANT CMYK images for the media only.

http://www.rqriley.com/press.html (2 of 4) [9/6/2002 08:03:38] Robert Q. Riley Enterprises Information for the Press

Trimuter 2 HydroRunner 2 G8-2 Jet

Technical Papers and Speeches Different Roads: Personal Mobility in the 21st Century is a comprehensive review of design option for future personal mobility. It was presented April 20, 2000 at the Northwest Alternative Fuels and Transportation Conference "Transportation 2000: Options for a New Millennium" Portland, Oregon Transportation Challenges of the 21st Century reviews the factors driving today's search for new automobile technology. It was presented by Robert Q. Riley on September 7, 1999 at the Museum of Modern Art in New York City, launching MoMA's day-long symposium on future car design (held in conjunction with the Different Roads: Automobiles for the Next Century exhibit). Automobile Design: Year 2010 and Beyond was presented at the J. D. Power & Associates Power Train Seminar in Troy Michigan on May 22, 1997 by Robert Q. Riley. The presentation reviews likely directions in automobile design. The Power of Design examines the impact of a product's design and its implied messages, and how packaging can have a powerful effect on consumer acceptance and expectations of new technologies.

Electric and Hybrid Vehicles reviews the state of the art of EV technology, and the most likely direction of future EV design. Energy Consumption and the Environment explores transportation energy use, its environmental impact, and possible options for the future. More Technical Papers In The News - Quotes Wired Magazine, March 2000: Wired magazine reports on the new line of CD-ROMs under development at Robert Q. Riley Enterprises. The Ambassador Magazine, August 1999: TWA's in-flight publication, features the Robert Q. Riley Enterprises website and plans-built vehicles. New York Times, May 19, 1999: In a feature in The New York Times entitled Even in Cleaner-Running Machines, Looks Will Count, writer Joseph Giovannini quotes Robert Q. Riley on his views about future automobile design.

EV Progress, January 15, 1998, reports on Robert Q. Riley's participation in the 1998 Washington Auto Show.

http://www.rqriley.com/press.html (3 of 4) [9/6/2002 08:03:38] Robert Q. Riley Enterprises Information for the Press

Quotes & Quotations: A collection of quotes and quotations. News Archives Company Information

Robert Q. Riley Enterprises Founded: 1986 P.O. Box 12294 Business: Design Consultancy Scottsdale, AZ 85267-2294 Phone: 480-951-9407 Fax: 480-368-2739

President/Owner Webmaster Robert Q. Riley Elusha Abdurakhmanov Biographical Sketch [email protected]

Media Contact Executive Assistant Robert Q. Riley Debi Kaiser [email protected] [email protected]

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http://www.rqriley.com/images/fig-14.gif [9/6/2002 08:03:53] An Urban Runabout Powered by a 12 kW Industrial Engine

UrbaCar

An Urban Runabout Powered by a 12 kW Industrial Engine

UrbaCar was featured on the cover of Mechanix Illustrated magazine in April, 1975, and started a build-it-yourself car boomlet that would last nearly ten years. The original prototype was powered by a 12 kW (16 hp) single cylinder industrial engine mounted in the rear. It delivered a top speed of 95 km/h (60 mph) and fuel economy in the order of 23 km/l (55 mpg). The design featured removable gull-wing doors and a 10 gallon fuel tank that would hold enough gasoline for nearly 965 km (600 mi).

UrbaCar tips the scales at a mere 295 kg (650 lb). Because its minimal curb weight, the small 12 kW (16 hp) engine still gives it a power-to-weight ratio about equal to that of the early VW Beetle. The simple drive train uses a continuously variable transmission (CVT), which transfers power to an oil-bath chain drive and then through a differential to the rear wheels. A standard automotive starter motor drives the car in reverse. The integral power train (engine, transmission, and final drive mounted on a sub-frame) is suspended from the rear of the chassis at four points using soft rubber mounts. This allows for easy removal of the drive package, and it effectively isolates vibrations.

Ultimately, UrbaCar went through three generations of improvements and nearly reached production in Kitchener, Ontario. Plans offered here are for the previously unpublished and vastly improved production chassis. A non- functional UrbaCar is on display at the American Museum of Science and Energy at Oak Ridge, Tennessee.

UrbaCar's body is built of FRP/urethane foam composite. For more information on the body construction method, click on One-Off Construction Using FRP/Urethane Foam Composite. Click on the images to the left to view large images.

For maximum compatibility, CAD plans are supplied in AutoCAD R12 level dxf

http://www.rqriley.com/u-car.html (1 of 3) [9/6/2002 08:03:58] An Urban Runabout Powered by a 12 kW Industrial Engine format on 3-1/2-inch disks. Other formats available on request include AutoCAD R14, R13 and R12 level dwg files.

Specifications Length: 116-inch (2946 mm) Engine: Kohler 16 hp@3600 rpm Width: 55 inch (1397 mm) Transmission: CVT Height: 48 inch (1219 mm) Fuel Capacity: 10 gallon F. Track: 49 inch (1244 mm) Seating: Two, side-by-side R. Track: 51 inch (1295) Fuel Cons: 55 mpg/23 km/l Weight : 650 lbs (295 kg) Range: 550 mi/885 km Max. Speed: 60 mph/95 km/hr

Plans Include...

10 - 24 x 36 inch drawings

36-page book

Price of Plans...

CAD: $75

Printed: $95

Both CAD & Printed: $150

http://www.rqriley.com/u-car.html (2 of 3) [9/6/2002 08:03:58] An Urban Runabout Powered by a 12 kW Industrial Engine Order Online or by Phone, Fax, or Mail

To Order Plans

● Online: Click on Order UrbaCar Plans to access the online Order Form.

● Toll Free Order Line: 1-800-230-2855 (USA only, weekdays 8:00 am to 6:00 pm MST). Note: For technical and other phone inquiries, please use our direct number: 480-951-9407.

Robert Q. Riley Enterprises P.O. Box 12294 Scottsdale, AZ 85267-2294 24-Hour Secured Fax Order Line: 480-368-2739 Toll-Free Order-Line: 1-800-230-2855 Technical Questions: 480-951-9407

http://www.rqriley.com/u-car.html (3 of 3) [9/6/2002 08:03:58] A Classic EV Design With Advanced Features

Urba Electric...

A Classic EV Design With Advanced Features

Urba Electric was introduced on the cover of Mechanix Illustrated magazine in February, 1977, long before the automotive world began thinking about manufacturing electric cars. Urba Electric's introduction was a landmark in EV development for a number of reasons. First, the car was ahead of its time simply by having been built at a time when EVs were considered non-starters by car makers. Second, MI readers collectively purchased over 20,000 sets of plans, which sent a strong message about public enthusiasm for EVs. Third, it was designed and built outside the automotive industry, and its development was entirely financed with private funds. And finally, although the car's 48-volt battery pack was little more than a copy of those used in golf cars, Urba Electric utilized cutting-edge composite technology in its construction, and it pioneered an innovative new concept in EV speed control and power system strategy. The car's technical innovations inspired engineers at Delco to purchase a set of plans and build one for testing. The Delco car later became known as GM's Drive I.

Urba Electric's main technology breakthrough was embodied in the Electromatic Drive Transmission. This ingenious and patented electronically controlled continuously variable transmission (CVT) let the motor run at a steady speed while the transmission's shift-position provided control over the car's speed from zero through 60 mph. The accelerator pedal was hooked to a device that varied a low-voltage shift-position signal to the CVT. This caused the shift-position to track the degree of depression of the accelerator pedal. As the accelerator pedal was depressed, the CVT smoothly upshifted causing the car to accelerate in unison. Meanwhile, the compound-wound dc motor ran at a constant speed - its most efficient speed. For regenerative braking, the driver simply let up on the accelerator pedal, causing the CVT to downshift to a lower ratio. Downshifting at cruising speeds forced the motor to spin faster, which reversed the direction of current flow and delivered a charge to the battery (due to counter emf) as it slowed the car. No traditional electronic speed control was necessary.

Urba Electric's chassis is not from an existing car. Instead, it was designed from

http://www.rqriley.com/urba-e.html (1 of 4) [9/6/2002 08:04:02] A Classic EV Design With Advanced Features scratch in order to keep weight down and efficiency up. The battery pack is arranged in a reverse "T" much like the battery pack of GM's EV1. Half of the car's eight 6-volt batteries occupy the space in a tunnel that runs between driver and passenger, and the other half runs transversely just behind the passenger compartment. The frame is made of rectangular steel tubing. A jackshaft coupled to a differential with a simple chain drive makes up the final drive, which is contained in a sealed oil-bath housing and suspended from the frame at the rear. The body is made of FRP/foam composite.

Today, the Electromatic Drive Transmission is no longer available, and plans include a substitute voltage-stepping speed control system and timing belt drive to the jackshaft, along with drawings of the original setup. With the low cost of today's power electronics, it is best to discard the voltage-stepping speed control in favor of a modern transistor chopper controller. Also, the trend today is toward much higher system voltages. Urba Electric's performance and efficiency would be enhanced by upgrading to a higher voltage. The most simple way is to switch to12-volt batteries. But in reality, anyone building this classic design should consider adding more batteries as well.

Urba Electric plans provide a technical insight into one of the most innovative and cutting-edge EV designs of the period. But building her today is not quite the paint-by-number project that it was when plans were first introduced - mainly because of the need to substitute new components where the ones specified in the plans have been phased out or replaced by newer hardware.

Specifications Length: 130 inches Width: 53-1/2 inches Height: 43 inches Front Track: 50 inches The car's speed and Rear track: 50-1/2 inches regenerative braking Wheelbase: 72 inches are controlled by System Voltage: 48 Volts the ingenious, electronically Motor: Jack & Heinz #G23 aircraft generator controlled Controller: Contactor controller Electromatic Drive Maximum Speed: 60 mph Transmission. Range: 60 miles Body Construction: Fiberglass/Foam composite It can achieve 60 mph on a battery pack that is virtually identical to those used in golf cars.

http://www.rqriley.com/urba-e.html (2 of 4) [9/6/2002 08:04:02] A Classic EV Design With Advanced Features

Range is about 60 miles on its diminutive 48-volt battery pack.

Order Online or by Phone, Fax or Mail

Plans Include...

14 - 17 x 22 inch drawings

32-page book

Price... $75

To Order Plans

● Online: Click on Order Urba Electric Plans to access the online Order Form.

● Toll Free Order Line: 1-800-230-2855 (USA only, weekdays 8:00 am to 6:00 pm MST). Note: For technical and other phone inquiries, please use our direct number: 480-951-9407.

Robert Q. Riley Enterprises P.O. Box 12294 Scottsdale, AZ 85267-2294 24-Hour Secured Fax Order Line: 480-368-2739 Toll-Free Order-Line: 1-800-230-2855 Technical Questions: 480-951-9407

http://www.rqriley.com/urba-e.html (3 of 4) [9/6/2002 08:04:02] A Classic EV Design With Advanced Features

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http://www.rqriley.com/images/fig-18.gif [9/6/2002 08:04:06] Three-Wheel Vehicle Handling Characteristics

Three Wheel Cars

Primary Factors That Determine Handling & Rollover Characteristics

by Robert Q. Riley with tilting three-wheeler contribution by Tony Foale

The idea of smaller, energy-efficient vehicles for personal transportation seems to naturally introduce the three wheel platform. Opinions normally run either strongly against or strongly in favor of the three wheel layout. Advocates point to a mechanically simplified chassis, lower manufacturing costs, and superior handling characteristics. Opponents decry the three-wheeler's propensity to overturn. Both opinions have merit. Three-wheelers are lighter and less costly to manufacture. But when poorly designed or in the wrong application, a three wheel platform is the less forgiving layout. When correctly designed, however, a three wheel car can light new fires of enthusiasm under tired and routine driving experiences. And today's tilting three-wheelers, vehicles that lean into turns like motorcycles, point the way to a new category of personal transportation products of much lower mass, far greater fuel economy, and superior cornering power.

Inherently Responsive Design

Designing to the three-wheeler's inherent characteristics can produce a high-performance machine that will out corner many four-wheelers. A well designed three-wheeler is likely to be one of the most responsive machines one will ever experience over a winding road. Superior responsiveness is primarily due to the three-wheeler's rapid yaw response time.

Yaw response time is the time it takes for a vehicle to reach steady-state cornering after a quick steering input. A softly sprung four-wheeler will have a yaw response time of about 0.30 seconds, and a four wheel sports car will respond in about half that time. A well designed three-wheeler can reach steady-state cornering in as little as 0.10 seconds, or about 33 percent quicker than a high- performance four wheel car.

Quick steering response has nothing to do with the number of wheels or how they are configured. It is

http://www.rqriley.com/3-wheel.html (1 of 5) [9/6/2002 08:04:11] Three-Wheel Vehicle Handling Characteristics a byproduct of reduced mass and low polar moment of inertia. A typical three-wheeler is lighter and has approximately 30 percent less polar moment than a comparable four wheel design.

Rollover Stability of Conventional Non-Tilting Three-Wheeler

A conventional, non-tilting three wheel car can equal the rollover resistance of a four wheel car, provided the location of the center-of-gravity (cg) is low and near the side-by-side wheels. Like a four wheel vehicle, a three-wheeler's margin of safety against rollover is determined by its L/H ratio, or the half-tread (L) in relation to the cg height (H). Unlike a four-wheeler, however, a three-wheeler's half- tread is determined by the relationship between the actual tread (distance between the side-by-side wheels) and the longitudinal location of the cg, which translates into an "effective" half-tread. The effective half-tread can be increased by placing the side-by-side wheels farther apart, by locating the cg closer to the side-by-side wheels, and to a lesser degree by increasing the wheelbase. Rollover resistance increases when the effective half-tread is increased and when the cg lowered, both of which increase the L/H ratio.

A simple way to model a three-wheeler's margin of safety against rollover is to construct a base cone using the cg height, its location along the wheelbase, and the effective half-tread of the vehicle. Maximum lateral g-loads are determined by the tire's friction coefficient. Projecting the maximum turn-force resultant toward the ground forms the base of the cone. A one-g load acting across the vehicle's cg, for example, would result in a 45 degree projection toward the ground plane. If the base of the cone falls outside the effective half-tread, the vehicle will overturn before it skids. If it falls inside the effective half-tread, the vehicle will skid before it overturns. To see a drawing showing a base-cone illustration of single front wheel (1F2R) and single rear wheel (2F1R) vehicles, click on: Single Front & Single Rear Wheel Comparison (23k).

The single front wheel layout naturally oversteers and the single rear wheel layout naturally understeers. Because some degree of understeer is preferred in consumer vehicles, the single rear wheel layout has the advantage in this department. Another consideration is the effect of braking and accelerating turns. A braking turn tends to destabilize a single front wheel vehicle, whereas an accelerating turn tends to destabilize a single rear wheel vehicle. Because braking forces can reach greater magnitudes than acceleration forces (maximum braking force is determined by the adhesion limit of all three wheels, rather than two or one wheel in the case of acceleration), the single rear wheel design has the advantage on this count as well. Consequently, the single rear wheel layout is usually considered the superior platform for a high-performance consumer automobile. But much depends on the details of the design.

Tilting Three-Wheelers (TTWs)

Tilting three-wheelers, vehicles that lean into turns like motorcycles, offer increased resistance to rollover and much greater cornering power - often exceeding that of a four wheel vehicle. And designers are no longer limited to a wide, low layout in order to obtain high rollover stability. Allowing the vehicle to lean into turns provides a much greater latitude in the selection of a cg http://www.rqriley.com/3-wheel.html (2 of 5) [9/6/2002 08:04:11] Three-Wheel Vehicle Handling Characteristics location and the separation between opposing wheels.

Consider that a motorcycle has no side-by-side wheels, yet it does not overturn when going around corners. A motorcycle negotiates turns by assuming a lean angle that balances the vector of forces resulting from the turn rate. The rider leans the motorcycle into the turn so it remains in balance with the forces that are acting on it. As long as the motorcycle's lean angle matches the vector of forces in a turn (resultant), it will not overturn. In order to stay in balance with turn forces under all possible conditions, however, a motorcycle must be able to lean at an angle of 50- 55 degrees before any part of the machine contacts the ground.

Three and four wheel vehicles can also be made to lean into turns. But with tilting vehicles equipped with side-by-side wheels, other physical and geometric realities come into play. For example, a vehicle having a wide body may contact the ground even at moderate lean angles, which will make it impossible to stay in balance with turn forces at the upper extremes. In addition, the greater the separation between the side-by-side wheels, the greater the wheel movement at equivalent lean angles. The movement of the side-by-side wheels can become excessive even at relatively small angles of lean in vehicles having a track approaching that of conventional automobiles. And the mechanical challenges of accommodating steering, bounce, and tilting, along with the angular limitations of CV joints on powered axles, places additional limitations on the lean angle of tilting multi-track vehicles. As a result, much of the recent work on tilting suspension systems has concentrated the three wheel platform. The Project 32 Slalom (1F2R) and the Mercedes F300 Life-Jet (2F1R) are excellent examples of modern tilting three wheel designs.

Free-Leaning versus Active Lean Control

Tilting three-wheelers can be free-leaning and controlled by the rider, just like ordinary motorcycles. However, if the mechanical limit of lean is less than is necessary to balance turn forces under all possible conditions, then some form of active (forced) lean control must be used to account for turns that exceed the lean limit. This is usually accomplished by hydraulic or electro-mechanical actuators operating on signals from an electronic control unit (ECU). Normally, the ECU processes signals from sensors that monitor lateral acceleration, vehicle yaw and lean angle, steering angle, and other relevant factors, then provides control output to the lean actuators. Another advantage of active lean control is that the operator is no longer required to balance the vehicle, as when operating a motorcycle. With active lean control, the vehicle is driven just like an ordinary automobile, and the lean control system takes care of the rest.

Rollover Threshold of TTWs

The rollover threshold of a TTW is determined by the same dynamic forces and geometric relationships that determine the rollover threshold of conventional vehicles, except that the effects of leaning become a part of the equation. As long as the lean angle matches the vector of forces in a turn, then, just like a motorcycle, the vehicle has no meaningful rollover threshold. In other words, http://www.rqriley.com/3-wheel.html (3 of 5) [9/6/2002 08:04:11] Three-Wheel Vehicle Handling Characteristics there will be no outboard projection of the resultant in turns, as is the case with non-tilting vehicles. In a steadily increasing turn, the vehicle will lean at greater and greater angles, as needed to remain in balance with turn forces. Consequently, the width of the track is largely irrelevant to rollover stability under free-leaning conditions. With vehicles having a lean limit, however, the resultant will begin to migrate outboard when the turn rate increases above the rate that can be balanced by the maximum lean angle. Above lean limit, loads are transferred to the outboard wheel, as in a conventional vehicle.

Tony Foale, author of Motorcycle Chassis Design, explains the behavior of an all-leaning-wheels TTW in terms of a virtual motorcycle wheel located between the two opposing real wheels. In a balanced turn, the resultant remains in line with the virtual motorcycle wheel. But in turns taken above the limit of lean, the resultant projects to the outside of the virtual wheel (vehicle centerline), according to the magnitude of turn forces in excess of those at lean limit. It's also important to note that the vehicle cg moves inboard as the vehicle leans into a turn.

When calculating the rollover threshold of a TTW having a lean limit, one must consider the inboard migration of the cg due to the angle of lean, the outboard projection of forces at the friction limit of the tires, and the traditional relationships between the cg height, the effective half-tread (at lean limit), and the wheelbase.

TTWs With Only One Leaning Wheel

Another interesting category of TTWs includes vehicles having only a single leaning wheel, such as the Lean Machine developed at General Motors in the late '70s and early '80s. GM's Lean Machine is a 1F2R design wherein the single front wheel and passenger compartment lean into turns, while the rear section, which carries the two side-by-side wheels and the powertrain, does not lean. The two sections are connected by a mechanical pivot.

The rollover threshold of this type of vehicle depends on the rollover threshold of each of the two sections taken independently. The non-leaning section behaves according to the traditional base cone analysis. Its length-to-height ratio determines its rollover threshold. Assuming there is no lean limit on the leaning section, it would behave as a motorcycle and lean to the angle necessary for balanced turns. The height of the center of gravity of the leaning section is unimportant, as long as there is no effective lean limit.

The rollover threshold of a vehicle without an effective lean limit will be largely determined by the rollover threshold of the non-leaning section. But the leaning section can have a positive or negative effect, depending on the elevation of the pivot axis at the point of intersection with the centerline of the side-by-side wheels. If the pivot axis (the roll axis of the leaning section) projects to the axle centerline at a point higher than the center of the wheels, then it will reduce the rollover threshold established by the non-leaning section. If it projects to a point that is lower than the center of the side-

http://www.rqriley.com/3-wheel.html (4 of 5) [9/6/2002 08:04:11] Three-Wheel Vehicle Handling Characteristics by-side wheels, then the rollover threshold will actually increase as the turn rate increases. In other words, the vehicle will become more resistant to overturn in sharper turns. If the pivot axis projects to the centerline of the axle, then the leaning section has no effect on the rollover threshold established by the non-leaning section.

In vehicles of this type that have a limit on the degree of lean, rollover threshold would be calculated as with an all-tilting-wheels vehicle operating at or above its limit of lean. In this case, the cg height of the leaning section would have an important effect on the behavior of the vehicle as a whole. Once a tilting vehicle reaches its limit of lean and locks against its limit stops, it can be analyzed as a non- tilting vehicle having the geometric configuration of the tilting vehicle at lean limit.

The front-to-rear incline of the roll axis of the leaning section is an important consideration with this type of vehicle. With free-leaning designs, the roll axis should project to the ground at the front (leaning) wheel. This is done to avoid a roll/lean couple, which could result in roll inputs during acceleration and braking. This is not as important in vehicles equipped with active lean control.

More Information

● Automobile Ride, Handling, and Suspension Design

● Mr. Riley's book: Alternative Cars in the 21st Century

● Trimuter Information Page

● Tri-Magnum Information Page

● Doran Information Page

● Transit Innovations' Project 32 Slalom Information Page

http://www.rqriley.com/3-wheel.html (5 of 5) [9/6/2002 08:04:11] Alternative Cars in the 21st Century

Alternative Cars in the 21st Century: A New Personal Transportation Paradigm

Robert Q. Riley

Published by Society of Automotive Engineers

By year 2030, the transportation sector will need 2-1/2 times more energy, just to keep up with expanding demand for motorized transportation. If trends are projected to year 2100, transportation will be consuming 20 times more energy, or four times more than is totally used by the world today. Cars will then have to be 20 times cleaner just to match the present burden their energy consumption places on the environment. Alternative Cars in the 21st Century: A New Personal Transportation Paradigm, published by the Society of Automotive Engineers (SAE), explores the paradigm shift necessary for designers, manufacturers and consumers in order to create a sustainable and environmentally friendly transportation system. According to the author, Robert Q. Riley, "nothing short of a holistic new approach will have much affect. Alternative cars as well as alternative energy sources are inevitable. Car makers are now investing vast sums to find new solutions, and the search for alternative fuels and power systems will ultimately reshape the automobile itself." Because most of an automobile's energy is consumed to transport itself, smaller cars designed specifically for urban and commuting trips are one of the most promising options. Studies show that such cars could slash the nation's fuel consumption by 50 percent and increase traffic flow in congested urban areas by as much as 70 percent. "It is already possible to build marketable and safe alternative cars that can exceed 100-mpg fuel economy, and the landscape is literally exploding with new technologies," said Riley. Practical battery-electric cars and fuel cell cars that run on hydrogen extracted from water or methanol are on the horizon. A new method of storing natural gas at low pressure on activated carbon could make it possible to refuel cars, boats and even lawn mowers from a standard residential gas line. Alcohol fuels made from plants and wood waste may soon be as inexpensive as gasoline. And a new high-speed flywheel module that fits into the space of a standard electric car battery can contain five times more energy than the battery it replaces. Today's accelerated search for new technologies comes from environmental, energy, and population forecasts. "If you add up the numbers and project them into the future, you end up with an

http://www.rqriley.com/alt-car.html (1 of 3) [9/6/2002 08:04:15] Alternative Cars in the 21st Century impossible set of conditions," said Riley. Approximately 400 million cars already exist, and by 2020 there will be over one billion cars in the world. In 100 years, most of the world will be industrialized, energy consumption will be 10 times greater, the environment will be overloaded, and the planet will have been stripped of its resources. The book's subtitle, A New Personal Transportation Paradigm, refers to the new mind-set and emerging technologies that will lead the design of future cars. "Future cars will be far different because of what we now know about the environmental harm and economic peril of unbridled energy consumption," said Riley. "And for those who enjoy fine machines, cars will also be better." Alternative Cars in the 21st Century: A New Personal Transportation Paradigm explains in layman's terms what can be done to improve fuel economy, and it reveals the latest information on electric cars, alternative fuels, advanced car designs, and new technologies that could make car crashes a thing of the past.

Chapters Include

● Private Cars Under Siege ● Personal Transportation Vehicles for the 21st Century ● The Technology of Fuel Economy ● Alternative Fuels ● Electric and Hybrid Vehicles ● Three-Wheel Cars ● Safety and Low-Mass Vehicles ● Alternative Cars in Europe

Reviews - Feedback

" A compelling book on the future of the automobile." Society of Automotive Engineers.

"As a former journalist and as an author, I have a profound respect for the power of the written word. As we look forward toward the beginning of a new century, new ideas, new perspectives, and new approaches to our society need and deserve careful attention." Vice President Al Gore

"We face an interesting dilemma as we attempt to reconcile the 'American dream' of open roads and automobiles, with environmental, economic, and safety concerns. Your insightful account of where we stand and where we need to go will be of great value as we face the transportation challenges of the next century." Senator Jon Kyl.

"In contrast to the typical book about future transportation, Riley's 'Alternative Cars in the 21st Century' turns out to be a gold mine of genuine technical information and insights on which the reality of the future will be based. He clearly conveys the key

http://www.rqriley.com/alt-car.html (2 of 3) [9/6/2002 08:04:15] Alternative Cars in the 21st Century tradeoffs in the systems engineering of a wide range of personal mobility devices -- treating safety, regulations, styling, and market forces as well as the technology of vehicle dynamics, propulsion, materials, efficiency, etc. I strongly recommend it for both professional and amateur." Dr. Paul MacCready, Chairman of the Board, AeroVironment, Inc..

"This study fills a void and describes many actual and proposed minicars of various sizes...Heavily illustrated with many photographs of old, new, and future small cars, and a very interesting review of the state of the art." J. C. Comer, emeritus, Northern Illinois University CHOICE (Association of College and Research Libraries).

Ordering Information

Price: $39.00, plus shipping charges (calculated by the Order Form according to destination). • Shipments to U.S. destinations go by Priority Mail. • Shipments to destinations outside the U.S. go by Surface Mail (Allow 4 - 6 weeks delivery). • Arizona residents, add 7.1% sales tax.

Order Alternative Cars in the 21st Century

http://www.rqriley.com/alt-car.html (3 of 3) [9/6/2002 08:04:15] LINKS...

LINKS....

To other resources on the Internet

Scroll Down

Alternative/Sustainable Energy

● The American Hydrogen Association: The American Hydrogen Association (AHA) is a non-profit association of individuals and institutions who are dedicated to the promotion of inexpensive, clean and safe hydrogen energy systems.

● David Rezachek's Home Page: This site contains information on renewable energy, efficient energy use, electric and hybrid vehicles, the environment, and more. You will also find many links to other related resources on the Internet.

Alternative Vehicles/Transportation Systems

● Ford Motor Company Hybrid Electric Vehicle program: This link takes you to the Ford HEV website. Get the latest information on Ford's hybrid electric vehicle program.

● Innovative Transportation Technologies: This very comprehensive site reviews more than 30 transportation technologies; some operational, some under development, and some conceptual. A must-visit site for anyone interested in innovative transportation alternatives.

● USCAR PNGV Page: The Partnership for a New Generation of Vehicles (PNGV) is a joint effort between the federal government and the U.S. automotive industry to establish global technical leadership in the development and production of affordable, fuel-efficient, low-emissions vehicles that meet today’s performance standards. Established on September 29, 1993, the alliance draws on the resources of seven federal agencies, the national laboratories, universities, suppliers and the United States Council for Automotive Research (USCAR), a cooperative, pro-competitive research effort between Chrysler Corp., Ford Motor Co., and General Motors. This is a page maintained on USCAR's website.

Global Warming and Climate Change

● United Nations Environmental Programme (UNEP): This site has the latest information on global warming and climate change. For a series of fact sheets on the causes and impacts of global warming and climate change, click on the "Climate Change" heading in their sidebar menu, then go to the "Information Kit" http://www.rqriley.com/links.html (1 of 7) [9/6/2002 08:04:21] LINKS...

area. An excellent series of papers.

Electric and Hybrid Vehicles

● California Energy Commission (CEC): Great site for EV and energy related information, as well as links to other sites.

● Department of Energy (DOE) Hybrid Vehicle Program: Information on Hybrid Electric Vehicles (HEVs) and updates on DOE's HEV program activities, which includes research by major U.S. auto manufacturers and subcontractors.

● Electric Vehicle Association of the Americas (EVAA): EVAA is a non-profit membership organization working to advance the commercialization of electric cars in the U.S., Canada, and Latin America. Their Web site contain news releases from member companies, EV industry and infrastructure information, and links to other EV related sites.

● Gorilla Vehicles: Producer of the world's first electric ATV, created by Rick Doran, designer of the Doran three wheel vehicle.

● HybridCars.com: Major automobile manufacturers are developing gasoline-electric hybrid vehicles in a push to dramatically lower vehicle emissions and increase gasoline engine efficiency. This site reviews the various offerings from the OEMs, and it provides technical information.

● Phoenix Chapter Electric Auto Association: The home page of the Phoenix Chapter of the Electric Auto Association (EAA). Site includes information on electric vehicle races, events, books, and their monthly meetings. The site also includes a listing of links to other EV related sites.

● Sacramento Electric Vehicle Association (SEVA): SEVA is an excellent source of up-to-date information and resources for EV enthusiasts and builders. They publish a monthly newsletter entitled "EVUpdate." Condensed copies of back issues are available online. SEVA is a chapter of the national EAA (Electric Auto Association). You can join SEVA ($15.00, then $10.00 per year), or print out a membership form online and join the national EAA ($35.00 per year). By joining the national EAA, you automatically have membership in the EAA chapter closest to your home.

● San Diego Electric Auto: San Diego Electric Auto offers a full range of electric automotive services ranging from complete vehicle conversions to machining and custom fabrication to fit the special needs of electric vehicles.

● Solectria Corp: Solectria is a designer and manufacturer of electric, hybrid electric, and fuel cell technology products, including individual components and kits.

General Automotive

http://www.rqriley.com/links.html (2 of 7) [9/6/2002 08:04:21] LINKS...

● Beven D Young Automotive Books and Software: This site offers a number of specialized automotive books. You'll also find a three-dimensional automotive suspension design program for design and evaluation of road and race car suspensions, and a simulation program for stroke engines.

● Society of Automotive Engineers (SAE): SAE Headquarters in Warrendale, PA, maintains the world's largest inventory of aerospace and land transportation technical information. Abstracts of books and technical papers can be accessed via their online search utility. You will also find information on events and activities, and how to join the SAE. This is a must-visit site for aerospace and land transportation professionals and enthusiasts.

● Society of Automotive Engineers (SAE) - Arizona Section: The Web site for the Arizona Section of the SAE. It provides information on local activities, programs and events.

● Eng-Tips Forums: Eng-Tips Forums are 900+ independent peer-to-peer non-commercial support forums for Engineering Professionals. Features include automatic e-mail notification of responses, a links library, and member confidentiality is guaranteed.

● M. W. Bourne Co: Company specializes in design, fiberglass products, and mold-making. Take a look at the motorcycle-based three-wheeler on the main page.

● Blade Chevrolet: Offers pre-owned cars, RVs, and commercial vehicles on the Internet. If you're shopping for a used vehicle, this company is worth a look.

Three-Wheel Cars

● 3-Wheelers.Com: This site offers a comprehensive look at three-wheel cars from their inception until now. The site contains lots of photos from owners and builders, plus historical information.

● Davis Registry (Davis Three-Wheeled Vehicle): The Davis Registry serves as a worldwide clearinghourse for information on the Davis three-wheeled vehicle, which was manufactured in California from 1947 to 1949.

● Jim's Page For Three Wheeling Cars: Jim's page provides info and links to a variety of three wheel cars on the Internet.

● Tilting Trikes: Max Hall has put up a page showing the various tilting trikes from around the world. These are three-wheel vehicles that bank into curves, like The Transit Innovations' Project 32 Slalom.

● Triking Cycle Cars: Here's a company that builds Morgan look-alike three-wheelers. They are located in the UK.

Human Powered Vehicles

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● International Human Powered Vehicle Association: Information, upcoming events and other Internet resources on human powered vehicles.

● Recumbent Cyclist News (RCN): If you want the latest information on recumbent bicycles, Recumbent Cyclist News is the place to find it.

Business, Marketing, Startup Information

● Entrepreneurial Edge Online: Interactive modules on all aspects of starting and growing a business, self- calculating financial management and assessment tools, archives of past magazine articles, and more.

Intellectual Property and Inventors Assistance

● Inventors: This site features weekly articles and net finds on a wide range of topics of interest to inventors. Topics cover a wide range of subjects including historical pieces and interviews with new product developers and inventors. Site offers much information, as well as links to many Internet resources for inventors.

● U.S. Patent and Trademark Office: Site offers much information on patents and trademarks, as well as a patent search utility.

● Delphion: This site provides on-line patent searches, as well as lots of related information on intellectual property. It is sponsored by IBM, and replaces IBM's prior patent search site.

● Trademark Now!: This link takes you to the site of Dracup & Patterson, a Santa Anna, California law firm that specializes in trademarks. You can apply for a trademark search and application online.

Build-It-Yourself Plans, Information, Materials & Services

Plans & Information

● Compumarine: Compumarine provides boat plans showing amateur boatbuilders how to build cedar strip dinghies and canoes. Plans include full-size patterns and a construction manual.

● Hoverclub of America: The Hoverclub of America, Inc. is where you'll find the most up to date information and news on hovering. They sponsor hovercraft events, and provide information on models, human powered machines, recreational hovercraft and large military hovercraft. Members receive their bimonthly newsletter, Hovernews.

● Mertens-Goossens NA - Boat Plans Online: This is a site oriented specifically to boat builders. They offer plans, books, supplies and kits.

● Stevenson Projects: This company offers plans to many projects that were featured in Popular Mechanics and other magazines. http://www.rqriley.com/links.html (4 of 7) [9/6/2002 08:04:21] LINKS...

● Popular Rotorcraft Association: The place to get info and network with others about homebuilt rotorcraft.

● www.rotorcraft.com: Information on gyrocopters and links to many aviation resources.

● Sport Helicopter & Pilot Global Information Exchange: Rotary wing info and links.

Materials

● Aerospace Composite Products: Fiberglass resin and cloth, plus much online information.

● Advanced Composite Materials: ACM distributes all types of composite support materials, including vacuum bag films, liquids, fabrics, kevlar, carbon fibers, fiberglass, and much more.

● Aircraft Spruce & Specialty Co: Suppliers of composite materials and aircraft components, catering to the home builder. They have several supply centers in the U.S. and elsewhere. Their "Last-A-Foam "is identical to the "Clark Board" specified in Doran plans.

● AM Castle Metals: Supplier of No. 321 stainless steel sheets for G8-2 jet engines. Thirty Sales Offices in the U.S. Phone: 1-800-BUY-CSTL. For best availability, purchase No. 321 stainless in most common sheet size of 36- x 120-inch.

● Composites One Inc: Composites One carries a full line of fiberglass materials and supplies. They have 14 locations throughout the U.S. and Western Canada. Visit their website for more information, or call 888-225- 5264 and your call will be automatically routed to the location nearest you.

● Fibre Glast Developments Corporation: This is the world's largest mail order source of fiberglass materials. They also provide tips on techniques and applications, as well as training videos and books on working with fiberglass.

● J & S Supply: Suppliers of urethane foam boardstock.

● Shopman Incorporated: Shopman is a retail and wholesale supplier of marine, industrial, composite, and fiberglass products. They are located in West Palm Beach, Florida, and will ship to your location. A good source for urethane foam and fiberglass materials.

● HKS Aviation: Company manufacturers a 60 hp air cooled twin that can be used for light aircraft and hovercraft.

● "600" Headquarters: A source for Honda AN 600 parts, some of which are used on UrbaCar and Urba Electric.

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● World Panel Products: World Panel Products will ship marine grade plywood to virtually any destination in the world. They carry a complete line of plywood and paneling products, including the 1/8-inch plywood used for Tri-Flyer and Pegasus. And their prices are reasonable.

Special Services

● Shields Premier Windscreens: This company produces top-quality polycarbonate windshields and windows for racing and other applications. Their windshields are produced with 100% optical clarity, and they can stand up to windshield wipers, chemicals, and sand pitting. They have a variety of stock windshields and canopies, and can make custom sizes and shapes as well.

● Policysure.Com: Policysure provides insurance for homebuilt vehicles, plus a whole range of insurances, competitively priced and 24 hours a day 365 days a year. You can get online quotes by answering just a few questions.

Miscellaneous

● Tony Foale Designs: Dedicated to the interesting subject of motorcycle chassis design. Lots of articles and photos. Principle source for the acclaimed book "Motorcycle Chassis Design" - the art and science. Tony Foale contributed the tilting three-wheeler information for our document, "Three Wheel Cars: Primary Factors That determine Rollover Characteristics," and was a contributing author to the Second Edition of Alternative Cars in the 21st Century. A must visit site for the motorcycle technical enthusiast.

● Aboard Boats & Yachts Market Ltd. A searchable listing of those in the nautical Internet boat market. Includes info on nautical events, boat builders, yacht brokers, and other related nautical sites.

● Aeromobile, Inc: A website showing hovercraft you can buy ready-made.

● Gyroscopic Inertial Thruster: An invention claimed to provide thrust through inertial forces.

● Industrial Designers Society of America (IDSA): Professional organization of Industrial Designers in the U.S.

● TKO Hovercraft USA: Company has a new hovercraft under development.

Search Engines/Directories

● Access Business Online is a powerful tool offering business oriented news, directories, http://www.rqriley.com/links.html (6 of 7) [9/6/2002 08:04:21] LINKS...

classifieds, articles, databases, international buyer-seller connections, BizWiz! and Q-Biz.

● The Source for Renewable Energy: A directory of over 2200 renewable energy-related businesses throughout the world are covered in this browsable directory. Includes electric vehicle manufacturers, component manufacturers, and businesses that convert conventional vehicles to electric vehicles.

● Alta Vista: One of the best search engines on the Internet.

● Dogpile: Simultaneously searches several of the most popular search engines.

● Excite:

● Findlinks: Findlinks provides industry-specific directories of World Wide Web sites. Automotive listings are divided into Trade and Consumer categories. ● Infoseek: Another one of the best search engines on the Internet.

● LinkMaster: One of the most unique search engines on the net.

● Lycos: An excellent search engine with lots of new ancillary services. If you haven't visited them lately, you'll find a vastly improved resource. ● WebDirect:

● WebCrawler:

● Yahoo: The world's most used directory.

If you would like to add your site to this list, click on the "Contact" link below and send the URL and a brief description.

http://www.rqriley.com/links.html (7 of 7) [9/6/2002 08:04:21] Robert Q. Riley Enterprises:Product Design & Development. Contact information

Contact

Robert Q. Riley Enterprises P.O. Box 12294 Scottsdale, AZ 85267-2294 Phone: 480-951-9407 Fax: 480-368-2739 E-mail: [email protected] .

President/Owner Webmaster Robert Q. Riley Elusha Abdurakhmanov E-mail: [email protected] E-mail: [email protected]

Media Contact Technical Support Robert Q. Riley E-mail: [email protected] E-mail: [email protected]

http://www.rqriley.com/contacts.html [9/6/2002 08:04:22]