Many of us have zero money, but this mega thirst for a go kart. The belt drive can be the most cost effect drive system that you could implement, on your low cost cheap go kart.
There are, however, issues with a belt drive that need to be understood prior to just diving in and making this belt drive system.
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First thing to understand is the final drive ratio. Is the engine actually going to be able to turn this system or will it stall. Keep in mind that the rpm for engagement is typically not very high, like 1200 rpms. So your calculation needs to reflect that. The HP curve for an engine is approximately linear, so if the rpms are decreased, then the HP needs to decrease accordingly.
For example a 5 hp motor will put out 87.5 in-lbs of torque at 3600 rpms. But the same engine will put out only approximately 1/3 of that at 1200 rpms (29.1 in-lbs of torque.)
Keep that in mind or you will be sorely disappointed when the go kart repeatedly stalls or burns up belts.
The second thing to understand is that a belt clutch is very hard on belts. Especially when neutral drops or high rev engagement are done repeatedly. The ideal is to have the belt engage at the lower rpm and then have the engine lug up to the desire cruising speed.
The third thing to understand is that pulleys are sensitive to heat build up and can if not selected properly fly apart or melt. The zinc die cast pullies, especially the small ones, are designed for fractional horsepower motors such as electric fans and so forth.
The sudden engagement will heat up the pulley to 300+ degrees F and cause the zinc or aluminum to melt and fly apart. Be sure to invest in a good quality steel pulley, especially if the pulley is being used as a clutch driver.
The fourth thing is that there is much debate over making belts go around corners, do twists or all sorts of design gymnastics, but the truth of the matter is that belts are designed to flex and carry loads.
The fifth thing is "What kills a belt?" Four things kill belts:
1. Sudden engagement (shock loads)
2. Prolonged Slipping
3. Poor Tracking
4. Improper load tension sizing
If you keep these four issues in check you will have a long lasting go kart drive system that will last years instead of weeks. And finally, belt drives, especially clutch belt drives, are very driver dependant. Like a clutch on a car, one poor engagement can wreck a clutch, the same goes with belt drives.
