Belt Drive Meditations

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4:42 AM
Jan 22, 2008
As most of you know, my next project is based on a 4 stroke design. After seeing that ocscully quit his belt drive project, I decided to kind of pick off where he left off. I found the source for the centrifugal clutch:

Scroll down to centrifugal pulley clutches. If I got a v belt, I could get a clutch assembly that wouldn't require a shim, it would just bolt right on. I would then need to run it to a jackshaft to get the reduction right. This is where I hit a bump. I can't find any v belt jackshafts anywhere. I would then need to put a pulley on the wheel, which I'm not sure how to connect either. I have 1/3 of the equation and need your help. The bike I'm using is a single speed Schwinn Corvette. If any fabrication needed to be done, I have access to MIG welders, grinders, etc.

Would I need to widen the rear stays? Where can I get a jackshaft? V belt or timing belt?

Any help is appreciated.


You are right I did lose interest in continueing my project back between Thanksgiving and Christmas and put the parts up for sale but am currently back to work on it as no one was interested in buying the various parts I already had.

Your questions about jackshaft kits. Most of the kits I have seen seem to come from the various Kart suppliers, and they are pretty much just the shaft and the bearings and the bearing holders. The V-belt or Timing belt pulleys would be purchased seperately. If you can't find what you are looking for with Kart suppliers you might want to check suppliers like Grainger or McMaster Carr. Timing belt pulleys and belts are another matter entirely, and are harder to find in the sizes needed to accomplish the reductions we need for our bike projects. Max-Torque has a couple of clutches with HTD Timing belt pullys attached for their final drive output and could perhaps be mated up to a GEBE Rear drive ring/sheve, thus avoiding the need for a jackshaft. The folks at Max-Torque seem to have a relationship with a company called Pfeifer Industries that manufactures the various driver and driven pulleys for timing belt systems but their web site does not provide pricing or availability information. The parts for the drive I have shown mocked-up for the GiantStone project, are based on parts from a company out of Arizona called VIZA Motors. They make go-ped type scooters and other misc. motorized toys. They even have the parts for building a jackshaft. As you continue to do your research on these various parts for Timing belt drive systems you will find that there are many different standards for these belts and pulleys. And all the pieces you intend to buy need to match up. A V-belt system will be much easier to put together and cause fewer clearence problems than a Timing -belt system.

As you have already found out there is no "one-stop shopping" source for all the various parts you need for putting together a drive system like this. And when you do find the parts there is a really good chance that you are going to have to modify them some what or build/fabracate special adapters to make them all work together. The other big draw back to attempting a drivetrain like this is the cost. Based on the research I've done over the past several months the total outlay for the various parts will run more than $300.00 and should not exceed $400.00. And that assumes I'm doing all the custom fabracation myself.

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I would strive to do a V-Belt system, mostly due to clearance issues and ease of assembly.

Assuming I bought the heeter centrifugal clutch, which would mate to the Honda with relative ease. I would then have to run it to a jackshaft which I could squeeze under my motor mount (I have clearance), and run it to my drive wheel sheeve. I found a source for for Whizzer Sheeves and the hardware to mount them. If I used that, would it require any reduction from the clutch, or would I still need a jackshaft. Actually...I think Whizzer's used timing belts, which I don't think I have the clearance for...

So, basically, I can't use a v-belt unless I use a jackshaft or if I can find a sheeve that's the right size for the rear wheel and find a way to fasten it to the rim. I was thinking of finding a narrow 20 inch wheel and find a way to make it accept a v belt or something. That's probably impossible though.

So, here are my options.

1. Centrifugal V Belt clutch to jackshaft to pully on wheel.
2. Centrifugal Timing Belt clutch to Whizzer rear sheave (would this ratio work?). I would have to widen my rear stays in order to make this work, but it's possible.
3. Centrifugal V belt to some sort of homebrew large sheave (20 inches or so). I wouldn't have to widen my stays because the belt is narrow enough.

Your estimate of 300 to 400 dollars, did that include the engine or was that just the drivetrain?
First, the Whizzer drivetrain uses V-belts. There is a smaller primary reduction to the jackshaft then a longer belt from a second small pulley on the jackshaft to the rear sheave. Actually the pully on the jackshaft is a stepped double pulley with the clutch built into it. The smallest clutch with a v-belt drive I have seen to date has a 3in. dia pulley. I think the Sheave for a Whizzer is maybee 18in. dia. thats only a 6 to 1 reduction. I think you need something in the neighbor hood of 17 or 18 to 1 total reduction. So Yes I do think you will need to use a jackshaft.

The dollars I mentioned in the previous post do not include the motor. The quote is for the clutch, jackshaft & its bearings & holders, 3 toothed pulleys and the various adapters to mount them and 2 timing belts.

I think that the easiest and probably least expensive system for you would be to purchase a sheave from GEBE ($40.00). Then contact the folks at Max Torque or better yet Peifer Industries to see what the smallest timing belt drive pulley they can put on one of their clutch bells, I think you need something in the neighbor hood of a 12 or 13 tooth driver. If they can't do one that small then buy one of the drivers from GEBE ($25.00) as well and then attach it to the clutch of your choice. Then all you would need is a longer belt that you can get from McMaster Carr for approx. $28.00 - $35.00. This system would give you the reduction you need with out having to use a jackshaft, and should not have clearence issues assuming you have the required room for the rear sheave.

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These plans use an extra wheel for the rear sheave, but I'd have to bend my stays. The plans aren't incredibly specific, but they just use a rear wheel padded with rubber in order to keep it from slipping. It also tells you to cut the chain stays and use a heavy piece of "tin" to repair it, using bolts. Seems sketchy.

I can't swing 300 dollars for the entire assembly, though. I'd need to do it cheaper. If it's not possible then I'd have to give it up.
So, my only question regarding this setup is whether the gears/drivers from Golden Eagle will just attach themselves to any centrifugal clutch? Could I get one with a sprocket and take off the sprocket? Or do I need one with a timing belt driver and replace it with the correct size?
So, my only question regarding this setup is whether the gears/drivers from Golden Eagle will just attach themselves to any centrifugal clutch? Could I get one with a sprocket and take off the sprocket? Or do I need one with a timing belt driver and replace it with the correct size?


I just spent some time looking over the various parts I recommended to you over on the GEBE web site, and feel that yes you would be able to braze or weld one of the GEBE drivers to a clutch bell. But first I would contact GEBE and ask for the specifics on their parts. What you want to know is the Pitch of their HTD (High Torque Design) drivers and belt. Its either 5mm or 8mm but you need to know exactly which it is. You also need to know the bore or what size shaft do they fit? You also might ask them what the belt width is in mm . Then I'd contact the folks at Max Torque and find out what the smallest driver they have available that matches the pitch of the GEBE. With luck they may already have what you need if they don't then tell them what you hope to accomplish and see if they can offer some help with getting the driver from GEBE attached to one of their clutches. My guess is that they will probably steer you to the folks at Pfiefer Industries for any custom work.
Or maybe Max Torque will sell you a clutch with a bell with no output driver and you can attach one your self. Based on the engine you are planning to use my guess now is that you will want either the 13t or 14t depending upon your riding terrain. Here is the link to the GEBE Parts page

I'm writing the email right now and will report back with my findings. What aspect of my terrain should I concern myself with when choosing a 13 or 14 tooth driver?

Thanks for your continued help. You've been more than generous.