Hints and Tips for Kart Builders:

ALLOWABLE POWER SOURCES: Electric, solar, biodiesel, SVO straight vegetable oil, WVO waste vegetable oil, methanol, ethanol, and pedal power.

The following is a list of possible propulsion methods your team may wish to investigate. This list is in no way exhaustive. We hope you explore other ways of making your kart, fun, fast, and safe. The overall goals are two-fold: The first is that students learn about alternative fuels, and secondly, that they learn the joys of seeing an engineering project through from conception to execution.

1. Electric Vehicle:

a. Use a 12 volt deep cycle battery to power an automobile, or truck, starter which is connected to your driven wheel via a chain. A “blip” switch on your steering wheel can be used to control a solenoid /relay to turn on and off the motor. BENEFITS: Cheap DRAWBACKS: Little motor control making car handling tricky

b. Use a 12/24/36/48 volt battery bank to control a similarly rated motor. Control the motor with a “motor speed controller” and an associated throttle control (potentiometer.) Many motor speed controllers are available on-line, including some easy-to-build kits for as little as $25. MSCs are themselves controlled by potentiometers (usually 2v-9v rating), and these can be configured to rotate either by pedal action, or handgrip control. Pre-assembled kits including all parts, the motor, and batteries, are available on eBay for less than $300.

c. Use a 12 volt deep cycle battery, connected to a properly rated inverter, to power the 120 volt motor and speed control assembly scavenged from a used tread-mill machine. Make sure your inverter can handle the maximum load of the motor (typically 1k-2k watts).

2. Solar Vehicle:

Because of the limited “real estate” of a go-kart, it seems impractical to build a kart capable of being driven competitively using just solar panels. However, building an EV go-kart such as described above, and charging the batteries with external solar panels is quite feasible. The Career Center electric kart is powered by energy generated by the school’s solar panel array. We invite any team to similarly charge their electric vehicle prior to the competition.

3. Biodiesel: A biodiesel kart will require a small diesel engine, but almost no other modifications to work. 3, 4, 5.5, 6, 10hp, and other small diesel engines are available either new on eBay (typically $300-400), or by asking at local lawnmower repair shops. Small diesels are commonly found on “set it and forget it” equipment such as farm water pumps, and small industrial generators. Serious equipment users appreciate the durability, and relative safety, of diesel engines.

Biodiesel fuel can be poured directly into the tank of a diesel engine and will operate as well as petro-based diesel fuel. Since our competition is in May, and the weather will be warm, we ask that teams use no more than a 20% biodiesel blend. We clearly urge you to use 100% biodiesel, however.

Installing the diesel engine on your kart may be as simple as swapping the gas motor’s centrifugal clutch assembly onto the diesel’s shaft, adjusting the chain length, drilling new mounting holes, and reconfiguring the throttle cable.

NOTE: The most common cause for a diesel engine not to run is that there is air in the fuel injection line. To fix, simply “crack” the nuts at the line junctions, and turn over the engine a few times. Working from the fuel tank out to the fuel injector, one by one close the nuts, and make sure you have fuel coming out at the top of the injector before closing the final fitting.

The most common cause for older diesel engines not to run, after you have made sure to purge the injector line of air, is that the rings are worn, and the engine isn’t developing sufficient compression. This normally requires an engine rebuild to repair.

4. SVO:

Depending on the type of oil used, and whether or not it needs thinning with heat, your kart can either be configured as a biodiesel, or a WVO.

5. WVO:

Waste Vegetable Oil karts will be slightly more complex than biodiesel karts because the oil must be heated to approximately 110O F prior to being injected into the engine. WE WOULD PREFER that you have two tanks on your kart so that you are demonstrating what it really takes to create a WVO powered automobile, or truck.

Most WVO cars (grease cars) start up on diesel, drive on WVO when that becomes heated after a few miles, and then shut down on diesel to purge the injector lines so they to not become clogged with solidified WVO as it cools. We would like to see you demonstrate that system on your kart, too.

There are various ways to heat a separate WVO tank on a go-kart. One way is through an electric immersion heater powered by either a battery, or the engine’s own generator system (if it has one). Another means is to use the exhaust pipe. Perhaps build a fuel tank around the pipe, or even use a separate heat exchanger system as on a nuclear powerplant, etc?

6. Methanol – Ethanol:

Absolutely the simplest way to go green racing is to convert an existing, running go-kart to run on these fuels. To do this you only need to re-jet the existing carburetor to a larger size, typically about 150% bigger for ethanol, and 200% for methanol. Because ethanol has only 34.7% oxygen, and methanol has 49.9%, you cannot interchange the fuels once you’ve jetted for one.

Ethanol does not have as much energy per volume as does gasoline, and it is also corrosive to some fuel intake components, most notably fuel lines and gaskets. Upgrade these to Viton, or other higher-quality materials. Larger jets are available at motorcycle or lawnmower dealers, although Harbor Freight sells a micro-drill kit for about $10 (www.harborfreight.com search for item 34640) so you can enlarge your own jets in increments until you find the right setting. The simplest way to check your jetting is to run the engine on the track for a few laps, and then check the spark plug color. You are after a very light brown. A white, powdery electrode means you are running too lean (open up the jet), while a black electrode means you are running rich, using too much fuel.

NOTE: The adjusting screw on the side of your carburetor adjusts the IDLE MIXTURE, not the running mixture. Therefore, your jetting work must be done on the main jet itself.

7. Pedal Power:

There is no greener power source than by using no fuels at all, however, pedal powered karts must still navigate the course, and the driver must be in a largely “seated” position. The upright position, such as found on a normal “safety” bicycle, is not allowed, though the laid back position such as found on a recumbent bicycle would be acceptable.