1 Basic Rail Vehicle Suspension Parameters
Presented by: Gary Wolf
Wolf Railway Consulting 2838 Washington Street Avondale Estates, Georgia 30002 404‐600‐2300 www.wolfrailway.com
Insert logo here in first Master slide Rail Vehicle Suspension Agenda 2 • 3 Primary Suspension Modes – Lateral, vertical, yaw/warp • Freight Cars – Springs and friction dampers – Yaw mode and truck warp • Passenger/Transit Cars – Springs and dampers – Lateral suspensions • Locomotives
Insert logo here in first Master slide 3 Primary Role of Suspension
• 1. Absorb vertical and lateral road shocks from perturbations in the track. Springs are used to slow down the accelerations over time, and store the energy. • 2. Dissipate the energy stored in the springs to prevent it from amplifying the motions of the road shocks and returning the energy back to the car. Dampers are used to dissipate the energy.
Insert logo here in first Master slide Energy Storage in a Spring 4
Insert logo here in first Master slide 5 Typical Motion Response of an Undamped Spring Displacement
Velocity
Acceleration
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Motion Response of a Damped Spring
Insert logo here in first Master slide 7 Vehicle Suspension Elements ‐ 3 Principal Modes
• Vertical Suspension • Lateral Suspension • Yaw/Warp Suspension
Insert logo here in first Master slide 8 Vertical Suspension
• Freight Cars – Secondary suspension springs between truck frame and bolster – Friction snubbers between frame and bolster – No Primary suspension • Passenger/Transit Cars – Primary suspension between wheelset and frame – Secondary suspension between frame and bolster, or frame and body • Locomotives – Primary and secondary elements
Insert logo here in first Master slide 9 Major Bodies Freight Cars
Car Body Truck Frame Truck Bolster Secondary Suspension Damper Secondary Suspension Springs
No Primary Suspension
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Spring: An Energy Storage Device
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Damper: Dissipates Energy
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Springs and Dampers Working in Parallel
Insert logo here in first Master slide 13 Major Bodies Passenger Car Body Vehicles
Secondary suspension supports carbody Bolster - swivels on truck
Truck frame - holds wheels in place
Primary suspension - lets wheel sets move up/down in frame
Insert logo here in first Master slide 14 Major Bodies Passenger Vehicles Car Body
Bolster Secondary suspension supports carbody
Truck frame - holds wheels in place
Primary suspension - lets wheel sets move up/down in frame
Insert logo here in first Master slide The Standard 3‐Piece Truck: 15 A long history of design improvements
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Bolster and Sideframe Interface Area
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Insert logo here in first Master slide 21 Nominal Wedge Position above top of Bolster
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Wear occurs on these 4 surfaces
Insert logo here in first Master slide Wedge rise above top of bolster due to wear 23
Insert logo here in first Master slide AAR Rule 46 (2007) 24
• Developed to address both friction casting front face wear, and total friction casting rise above top of bolster. Rules applicable when: – At any time of inspection – When car is on repair track • Rule 46 also addresses gib wear, centerbowl clearance, and column plate wear
Insert logo here in first Master slide Common Friction Casting 25 (Wedge) Designs
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Worn Out Friction Castings (Wedges)
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> 1 13/16” (~1 ¾”) Condemnable Per Rule 46
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> ¾” Generally Condemnable Per Rule 46 (Check Rule for exceptions!)
Insert logo here in first Master slide Barber Variable Damped Trucks ‐ Allowable Wedge Rise AAR Rule 46 29
Be Careful!!
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787-C Wedge ½” Wedge Rise
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Ride Control Gage
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ID
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Insert logo here in first Master slide Spring Groupings 34
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Count Springs; Verify Type; Verify Inner and Outer Springs; Check Free Height
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AAR Designated Spring Groups
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Right Side
Left Side; Missing corner inner coils
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Spring showing sign of fatigue/set
Insert logo here in first Master slide 40 Checking Free Height
Insert logo here in first Master slide 41 Broken Spring
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Solid Spring – Indicates Excessive Rock/Roll
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Truck Frame Swing Hanger Bushings Primary Suspension Pedestal
Tie Rod Bolster
Side Bearings
Secondary Suspension Equalizer Spring Plank General Passenger Swing Hanger Truck Components
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LOAD PATH
Secondary Suspension Truck Bolster
Frame Primary Suspension Equalizer
Spring Plank Basic GSI 70 Suspension
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Equalizer Springs Primary Suspension Truck Frame
Equalizer Bar
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Secondary Suspension Spring Plank
Equalizer Springs Primary Suspension Insert logo here in first Master slide 47 Air Spring Secondary Suspension Between Bolster and Car Body
Insert logo here in first Master slide Amfleet Passenger Car Trucks 48
Primary suspension at each journal
Shock Ring
Insert logo here in first Master slide Light Rail Vehicle Suspension 49 Air Spring Secondary Suspension Between Bolster and Frame
Note: vertical damper
Primary suspension at each journal
Insert logo here in first Master slide 50 Amtrak Superliner Car
Wagon Union Truck
Insert logo here in first Master slide Amtrak Superliner Car 51
Primary Suspension
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Secondary Suspension
Insert logo here in first Master slide 53 Locomotive Suspensions
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Primary Suspension
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Secondary Suspension
Insert logo here in first Master slide 56 Genesis Trucks
Insert logo here in first Master slide 57 Dampers
• Mostly hydraulic or friction style used on passenger cars • Used to absorb lateral and vertical shocks from track • Dissipates Energy from spring suspension • Restores ride quality
Courtesy Koni Company
Insert logo here in first Master slide Hydraulic Dampers ‐ 58 Construction
Courtesy Koni Company
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Typical Transit Car Vertical Suspension Showing Hydraulic Damper in Parallel with Air Spring
Insert logo here in first Master slide 60 Friction Dampers
Courtesy Vibratech Company
Insert logo here in first Master slide 61 Dampers ‐ Inspection Items
Insert logo here in first Master slide 62 Lateral Suspension
Insert logo here in first Master slide 63 Lateral Suspension
• 3‐Piece trucks have relatively poor lateral suspension characteristics, relying primarily on shear stiffness of load springs and friction damping due to wedge motion • Passenger/locomotive trucks have improved lateral suspension relying on both swing motion of the bolsters, shear of the secondary springs, and bump stops. In addition, lateral shock dampers are used.
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Bolster & Lateral Bump Stops
1” Nominal Bolster Stop to Body clearance; +1/4”, -0” tolerance
Lateral Bump Stops
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Side Bearing
Lateral Secondary Suspension Elements of Typical Transit Car
Showing Damper and Air Spring.Insert logo here in first Master slide 66 Yaw/Warp Suspension
Warp Stiffness Sideframe to Bolster
Warp/Yaw Stiffness Wheelset to Sideframe
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Warp Stiffness Sideframe to Bolster
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Warp/Yaw Stiffness Wheelset to Sideframe
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• Yaw/Warp Stiffness influences two primary responses – Hunting (high speed stability) – Truck Warp (Curving) • Freight Cars depend on the friction wedge system for warp stiffness • Passenger cars are normally rigid frame possessing high warp stiffness, but typically possess lower yaw stiffness
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90 Degrees Truck Hunting Lateral Instability
Wedges Help to Keep Truck Square
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Hunting Oscillation of a Tapered (Conical) Wheelset
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Insert logo here in first Master slide Truck Hunting 73 Truck Stable Bolster Sideframe Remains Square Out of Square
Friction wedges Friction wedges worn provide squaring force providing no squaring force
Insert logo here in first Master slide Hunting Speed Response 74 Hunting Severity Critical Speed for Hunting Prone Cars BH, ET, EF, EG
Lateral Critical Speed for G’s Most Cars
Speed MPH
10 20 30 40 50 60 70 80 Insert logo here in first Master slide 75
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Ideally, a truck should remain “Square” during curving to allow radial alignment of wheelsets with curve
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Insert logo here in first Master slide 80 Barber Frame Brace Truck
Frame Bracing increases the warp stiffness of the truck improving both high speed stability and curving.
Insert logo here in first Master slide 81 The End
Truck Suspension Basics
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