How to Build a Low-Cost Competitive Green Go-Kart



How to Build a Low-Cost Competitive Green Go-Kart

By William Longyard

Introduction:

If you are starting a “green” karting team from scratch, you’ll find that it is not very difficult once you have acquired the most expensive piece of equipment, the engine. For many teams, you have borrowed an engine from the Career Center and so this expense is eliminated. If you are buying your own engine, expect to pay $375-$550 for an air-cooled diesel engine. Other options are available, including electric, but those will not be covered in this short monograph.

So, with an engine in hand, your next move is to mate it with a suitable kart chassis. You can purchase the components to build a chassis, including frame, wheels, tires, brakes, cables, etc., but building a kart this way tends to be very expensive. A better way is to find a USED kart, and simply adapt your diesel engine (or electric motor) to it. Typically, a used kart on can be had for $100-200.

When searching for a suitable used kart, you should find one that has a real racing chassis, with real racing wheels. There are many go-karts out there that have sturdy, rectangular frames, with good control systems, and good treaded tires, yet these karts are not suitable for sustained laps on a tarmac surface. Their tires will shred down after as few as ten laps, and due to the poor geometry of their frames, they will be hard to steer, hard to brake, and impossible to make corrective adjustments to. Worse still, the bearings used in these wheels can disintegrate under racing speeds, and cornering loads, and lead to kart failure.

This is the type of chassis you DO NOT want.

We recommend that you find a chassis that was designed for racing. These are available used for just a little more than a rectangular one, but will save you money and time in the future. Your team will also have a much better chance of winning the race!

This is the type of chassis you DO want (or similar).

The tires and wheels that you should look for have NO TREAD (called slicks) and are AS WIDE, or WIDER than they are tall. You DO NOT want a tire/wheel combination that is narrower than tall, and has a tread (commonly available at hardware, and industrial supply stores).

An aluminum racing wheel with a racing

tire (slick), the recommended combination.

“Service cart” wheel and tire of the type not

recommended, though these are commonly used

on many go-karts.

Go-Kart Systems

Think of your kart as nothing more than a collection of five systems, listed here in order of importance:

a. Brakes

b. Steering

c. Fuel

d. Chassis/Drive train

e. Wheel/Tires

Let’s go through these one at a time and look at features you should include on your kart.

A.) Brakes:

Stopping a kart safely is your team’s number one priority because it is the key to driver, and spectator, safety. A fully developed go-kart can reach 80 mph and is potentially dangerous. Here at the Career Center, because of the race course design, karts rarely get above 25 mph. Still, a kart MUST be able to stop quickly when the driver applies the brakes, and so this must be your team’s main area of focus.

There are numerous designs for safe go-kart brakes, and rather than go into detail on all of them, we will present a range of effective brake systems that you should consider. IF IN DOUBT, contact us for further advice, or contact a local go-kart shop (Competition Karting Inc. in Welcome, NC is very helpful.)

1. Tire Friction Pads- In this system, a tube stretches across the rear of the frame just in front of the rear tires. When the brake pedal is depressed, a rod actuates this tube to which are attached two small metal pads which press against the rolling tires, thus causing friction to slow down the kart. This system is effective at lower speeds, and is acceptable from a safety check standpoint. However, it is the least effective system.

2. Brake Shoes and Drum- Just like a full-size automobile, there is a brake drum with internal expanding shoes that cause friction when the brake pedal is depressed. This is a very good system that is simple, and reliable. The pedal free-play should be checked, and minimized, before each race.

3. Rotor and caliper- Also as found on full-sized automobile, a brake rotor is attached to the rear axle either directly, or via fitment to a wheel hub. Pressing the brake pedal either operates a mechanical, or hydraulic, linkage to a caliper which then clamps down on the rotor. This is the best form of braking, and can be adapted to any kart. The down-side of the system is the expense. This system is found on most racing karts.

B. ) Steering:

Steering is relatively straightforward on go-karts. The wheel is connected via tie-rods to the steering knuckles on the wheel spindles. Some tie rods actuate under the steering column, and some above it. It is important to make sure that no matter what the arrangement the linkages don’t interfere with the driver’s feet or legs. From a safety standpoint, rod ends should be checked frequently for tightness, and the front wheels should be adjusted for about 1/16th inch of toe-in. Failure to properly align the steering gear will result in more tire scrub, which will allow for faster tire wear, and difficulty in steering. We also recommend that all steering components be secured with at least lock-nuts, or even better, castellated nuts and safety wire.

C. ) Fuel:

The Go Green Go-Kart competition does not allow the use of any type of fuel other than vegetable oil, waste vegetable oil (WVO), or biodiesel. We can provide your team a suitable amount of fuel on race day, though not for practice sessions. A Career Center sponsored methanol kart, and a propane kart, may participate as technology demonstrators, but no other teams may bring karts using these fuels.

All fuel must be stored in DOT approved containers, and the on-board fuel tank must pass safety inspections. A fuel shut-off switch (petcock) must be VISIBLE and CLEARLY MARKED.

Battery powered electric karts are encouraged to participate.

D.) Chassis / Drivetrain:

As you prepare your kart, make sure all the joins and welds on your kart are sound, and that there are no cracks or failures. Electrical conduit, or mechanical tubing, has no place on a kart, and should not be used to repair failed tubing, or to build a roll-bar. There are various welding methods for attaching brackets, or an engine plate, to a frame, and if you are not familiar, or skilled enough, to use these methods, please contact us at the Career Center and we will help you with these. An engine plate bolted to a kart frame IS NOT SECURE.

If you need to make, or relocate, an engine plate to fit the diesel engine, you can purchase a plate with mounting slots already punched out from either Competition Karting Inc, in Welcome, NC, or from Northern Tools in Colfax, NC, just outside of Kernersville.

Use an engine plate welded to your frame

to mount the diesel engine.

Make sure the engine’s direction of rotation matches that of your driven wheel before you weld the engine plate in place. You don’t want your kart going backwards! Before welding, also make sure that you attach a centrifugal clutch, and chain to the engine, and run the chain down to the drive sprocket on your axle (or wheel hub.) Take a flat edge (ruler), and make sure the chain lines up EXACTLY in the plane of the two sprocket before welding the plate in place permanently. Failure to line up the chain properly will result in a snapped chain, or prematurely worn out sprockets. Make sure, too, that your drive plate slots are exactly parallel to the longitudinal axis of your kart frame. You will need to adjust the engine position fore and aft to tighten the chain after it stretches from use.

Centrifugal clutch: the 6 hp diesel engine takes

a 1” bore clutch. The 4 ½ hp uses a ¾”.

Once your drive train is in place, you must build a STEEL safety guard around the chain and sprockets so that neither the driver, nor crew, can accidentally get caught in the moving components. The safety guard itself must be securely fitted to the kart so that it cannot shift position, or fall off, during use. Failure to comply with this stipulation will result in your team not passing the safety inspection prior to the race.

All engines (including electric motors) must have a VISIBLE and CLEARLY LABELED cut-off switch. Electric motors need only have an electrical kill switch (available inexpensively at Harbor Freight Tools in Winston-Salem), while a diesel engine kart must have BOTH a fuel cut-off valve (petcock), AND an engine kill switch. Since diesel engines do not operate with an electrical ignition, the only sure way to kill them immediately is by opening their decompression lever. The engines provided by the Career Center have red plastic tabs on their decompression levers BUT THESE ARE NOT GOOD ENOUGH FOR EMERGENCY USE. You must rig a larger, more visible cut-off lever on the kart that can be accessed immediately by someone NOT in the kart, and the driver, too. At the Career Center we have done this be running a “pull down” cable to the decompression lever that extends to a larger lever by the driver’s left side. THIS LEVER IS A CRITICAL SAFETY FEATURE. Failure to rig a suitable kill switch will disqualify your team from the competition. WE USE THESE SWITCHES CONTINUOUSLY. Please contact us if you would like help in rigging a safe kill switch.

As a general practice, we recommend the use of lock-nuts on all components of the kart EXCEPT those connected directly to the exhaust system. Best practice is to use castellated nuts and safety wire on any component subject to high vibration.

[pic]

E.) Wheels / Tires

As previously mentioned, you should try to use racing wheels with racing slicks, but these are not strictly necessary. Treaded “service cart” wheels are used on many go-karts, though they work better on dirt tracks than on the tarmac which you will find on the day of the competition. The bearings in “service cart” wheels have a very short life under competition loads and can even fail. Typically a failed bearing will cause the wheel to flail on the end of the axle with some loss of steering control. If you choose to use service cart wheels we recommend that you examine the bearings for tightness. Replace loose bearings with go-kart rated bearings (Competition Karting, Inc.). These are very inexpensive. Make sure, too, that the bearings are well packed with bearing grease.

The science of racing tires, weight / balance, off-set, camber / caster, etc., is beyond the scope of this monograph, but suffice it to say that if you build a competitive kart, you can win, or lose, depending on how your rubber meets the road. Chemical tire conditioners sold at kart shops will promote adhesion, but are not commonly used at the

Go Green Go-Kart Competition.

SAFETY:

We touched on safety several times thus far, but all team members, and the team’s sponsors, should be mindful of the old racing saw that the most important part on any race car is “the nut behind the wheel.”

Driver safety is paramount, and assuming you have built a safe kart, the next step is to make sure your drivers are competent. This can ONLY be done through practice behind the wheel. Set up a mock course in a disused parking lot and let your drivers learn how to control the vehicle at various speeds and in various driving configurations (turns, straights, chicanes, etc.). MAKE SURE all drivers are helmeted with an approved DOT certified helmet, and that they are wearing a jacket and long pants to protect their elbows and knees. These are requirements on competition day and should become habit prior to the event.

MAKE SURE, when practicing, you have all the safety features in place on your kart, and functioning, including good brakes, an engine kill switch, and a chain guard.

Everyone is responsible for creating the safest kart they can. This is best done by doing research on the current technology, and talking to people who actually have karting experience. There are many more of these people in the community than you might expect. There are books, DVDs, on-line groups, etc., dedicated to the sport of kart racing and you should learn good safety practices from them.

DO NOT attempt to build a kart on your own unless you know you have the skills to assemble it safely. Building your own kart will be a great learning experience for everyone if you allow yourself to be guided by people who are familiar with the requisite fabrication processes. We are only too glad to HELP YOU here at the Career Center with your project, and will be glad to TEACH YOU the skills if you so desire.

NOT EVERYONE is cut out to drive karts fast. Do not push someone into the driver’s seat who is uncomfortable with the prospect of driving fast. However, urge all of the team’s participants to try to learn as many new skills as possible. Remember, the motto of the Go Green Go-Kart Competition is:

In the End, Nobody Wins Unless Everyone Wins!

See you at the races!

Bill Longyard

Resources:

Competition Karting, Inc.

9 Austin Lane

Welcome, NC 27374

(336) 731-6111

Harbor Freight Tools

2680 Peters Creek Parkway

Winston-Salem, NC 27127

(336) 771-2323

Northern Tools

8521 Triad Dr

Colfax, NC 27235

(336) 996-8655

Estimated Costs:

Engine: Free

Used Kart: $150

Clutch: 100

Engine Plate: 15

Miscellaneous: 100

Total: $365.00

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WARNING: The engines provided by the Career Center all have throttle adjustment levers with a knob that can lock the throttle at a chosen position. This knob can be a SAFETY HAZARD. We have had two experiences where this knob vibrated to the closed position and locked the throttle of a kart in a nearly wide-open position. In one case this caused the kart to crash, and the driver narrowly escaped injury. YOU MUST REMOVE THIS KNOB. If you have any questions about this, please contact us for assistance.

YOU MUST REMOVE THIS KNOB.

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