Belt Drive in a Vibrating Environment

I didn't think it was feasible, but I just googled, "Belt driven racing motorcycles", this is one of the sites that popped up, http://www.banditmachineworks.com/sportster.htm#belt

might be worth giving them a call and seeing what they say.

Could you recommend any companies whom I should talk to?

Talk to Gates.

A belt is better at absorbing shock than a chain, and of course a belt deals better with lack of lubrication.

As you can see from a Harley drive, the belt is wider than the equivalent chain, which can be a problem, or not, depending upon application.

If the driven end is unsprung, then inertia loads (from bouncing around with the wheels) will be less than for a comparable chain. Maintaining correct tension can be a concern, however, just as it is in a chain drive. In the ideal geometry, the drive sprocket and the suspension pivot are on the same axis. Better yet is to make the differential rigidly mounted, of course, which makes life easier on the belt, and improves suspension performance.

Off road mini Baja car? Like with sand and dirt all around? With sudden applications of high power? And hard shock loads? IMHO, I would be afraid of sand embedding itself into the friction surfaces of the belt, causing the friction to go away.

Way outside the box would be hydraulic drive motors bolted to the wheels. Then the power could be transmitted by flexible hoses, and be self lubricating. It also opens up the suspension to move in any direction you want it to.

nah, it's a toothed belt

so friction isn't what makes the sprockets go round & round

but there isn't a way to to keep the sand & other crud from packing in the belts & sprockets

causing both stretch & derailing..

Hughes 300 (helicopter), New York Blower (industrial fans) , and many other types of equipment use belt drives many thousand of hours per year. Is there maintenance to each system, yes, but, not nearly as much as chain drives. I would say your on the right track. As others stated here, speak to one of the rep's from "Gates" or others and they will help you with proper sizing. Good Luck and lets know how it works out.

I have worked on tree chippers that had large Ford V8 engines and others with Detroit Diesel engines running arbors with spinning blades that weighed over 1,000 pounds that had only belts for drive. But they were v belt design, and were 3 belts wide joined at the top surface. And these belts were well shielded from any debris getting to them. Also they were not being used in sandy, dusty conditions.

Thanks for the replies. I figure that if the belt drive is properly enclosed, dirt and debris isn't so much a concern, however it does require tensioning and this is more important as the driven end is the final axle which is unsprung.

We have been looking at Gates Poly Chain GT2 carbon fiber belts. Would you know if the tensioner for belts would be in any way less complicated than that of a chain? I wonder if the tensioner could just be a wheel running on the belt instead of an idler pulley like a chain would require.

spring or fixed position tensioner for belts are about the same as a chain

the idler should be on the return side.

an idler on the inside should have teeth to avoid damaging the belt

a design that the output or the axle pulleys move to provide proper tensioning, has some advantages

I've used these belts in industrial applications [100hp], they really don't stretch & will far out last chains.

one limitation is the minimum size of drive pulley, which would tend to make the entire assembly take up more room & more cover to enclose.

this is probably one one the biggest reasons you don't see belt drive motocross bikes. the other factor is the width. A #50 chain is narrower than a belt. doubling or tripling the width of the drive elements would introduce a bunch of problems to the design of a bike.

Would you know if the tensioner for belts would be in any way less complicated than that of a chain?

It is apt to be the other way around. Most motocross bike chain tensioners slide on the chain, rather than rotating (they are solid plastic blocks). A toothed belt tensioner must rotate to avoid damaging the belt. The diameter of the idler pulley should be ample, to reduce the angular flex (and eventual fatigue) at the tensioner point. Thus, the tensioner will be more complicated, larger, and heavier.

In motocross bikes, the chains are exposed, and as a result have no guard to collect mud and dirt, which can slip through the gaps in a chain. Such stuff will be more likely to pack the grooves of a toothed belt sprocket, leading to over tension, possible tooth jumping, etc. A small stone has about 3 times the likelihood of finding its way under the belt, (very likely causing damage) by virtue of the greater width of a belt.

A good belt enclosure, built to take the occasional grounding, would more than cancel any weight advantage of a belt drive. (The overall weight of unguarded drives is already pretty close, due to the larger diameter, thicker pulleys used for a belt.)

I am inclined to agree with the guest poster (post 8). Even for factory teams, where there is budget available for experimenting and optimizations, chains are used.

A condition similar to what you describe is Motocross racing.Shock loads,dirt,grit, and all types of physical abuse.Look at what they use, for they are on the cutting edge of any new developments.They still use chains because in that type environment it is the best solution.Lubrication is important, but don't use a thick spray grease.Use a very thin oil,like turbine oil, that will penetrate into the bushings and not leave a sticky surface for dirt to cling to.Trust me on this, although it is contrary to popular belief. Thicker is not better.

I have been racing motocross for many years and this method gives the longest chain life.

Use a friction block instead of an idler gear for maintaining tension.This helps clean the chain instead of packing dirt into the joints.Any dirt bike parts supplier will carry these idler blocks made of a super tough polymer.

Good luck.