Weedeater belt drive

Aug 8, 2019
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I have a very very strong running high revving 31cc bolans bl100 engine it starts very easy also. The nut holding the flywheel tight to the crank was a press fit inside the pulley. The nut was also flush welded to the pulley. Then the pulley just screws right onto the crank to hold the flywheel tight. Welded the starter dogs to the pulley also. Now I'm trying to figure out an in frame mount and I'll be using a kids bike rim as a rear tire pulley. Anyone ever have luck with belt drive?
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Aug 8, 2019
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Well my buddy pointed out the lot of air compressors at the dump that have some pretty big pulleys on them. Maybe I'll go down sometime and check those out. I'm sure a pulley could be welded right to the spokes of the back rim. Like a solid mounted rag joint setup. Also I'll have a short video up on this thread tonight showing how well this 31cc bolans runs.
 
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MEASURE TWICE

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Besides rag joint or clamp on hub for sprocket, see the Whizzer Clone Sheaves sold. I think 40 to 50 dollars back 3 or so years ago on ebay. I made my own clamp to spokes, but washing machine aluminum pot metal pulley cracked twice. Nothing could I find in pressed stamp steel used or new for reasonable price, so it was best option. I had to grind down the butt joint weld of the stamped steel sheave as it was not smooth. Dremel and hand sand it was done. Also they use those distorted threads that are meant to never be able to disassemble. I drilled them out and used nylon lock nuts and split lock washers. Centering is supposed to be ever so slightly possible on these, but it was not as good as my home made sheave. It may have gotten a little off center for some reason. Truing the spokes I don't think would help much, it is just a little funky how the clamps can only move fraction of an inch. Weld, brase, solder, not sure to spoke though. I can always learn of something new! For engine gearing I had 20:1 ratio with 26 inch wheel and 3hp Briggs 4 stroke, that had good torque. 12:1 ratio with 26 inch wheel and 3.5 Briggs 4 stroke goes fast, but up hill not as well. I'm using that now as the 3hp need some work. If I can buy a centrifugal belt clutch to use with the 3.5hp I would, but the shaft is too short. Chain type clutch means expensive large sprockets. I may see about taking the crank from one if it fits in the other engine and use belt clutch again.
 
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Aug 8, 2019
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I forgot my camera last night so no video of the 31cc running till tonight. Anyways the pulley I used on this small two stroke was very thick metal and has some nice weight to it. I noticed it sort of acts as a flywheel weight! Engine doesn't scream till it bogs anymore cause there is no weight on the flywheel. it's more of a steady high Rev at full throttle now. The bolans and pulley were free so was the bike. And I have no cash to put into this project. So I'm gonna have to get creative with the rear pulley and engine mount. I have a junk washer that i never even thought to check for a pulley so thanks for that bit of info!
 
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Aug 8, 2019
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I'm not sure how this would work out in terms of gearing? But it sure would be easy for me to weld this crank pulley off a Gen1 Chevy small block onto the rim of the bike I'm using. Not looking for a bunch of speed. Just enough power to cruise on the backstreets with..
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Ok so this whole idea could work out just fine or be a massive failure I'm planning on using the side hang mount typical friction drive's use but instead of hanging over the rear tire I'm gonna hang it inside the frame. If I CAN get it mounted to the bike frame itself then the hardest part would be done. It all comes down to being mounted and the front pulley being able to line up with the rear pulley. I think i would have to spread the frame apart that the rear wheel bolts to so the pulley can clear the frame. The next hard thing would be a old style belt clutch.
 
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This is going to be a very long process i'm guessing I have no motivation to go work on the mount but all I have to do is drill a tiny hole for a dow pin and another hole for the bolt then the angle iron will hang the engine right inside the frame. At first glance it looks like the pulley's could line up just fine.
 
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MEASURE TWICE

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1ST The sandwich type clamp to spoke washing machine pulley photo
you can see the weakness is the pulley white metal aluminum is weak

You however have a steel pulley which is good.

45 years ago I used the washing machine pulley that was the similar tab type with center hub to connect to shaft of washing machine motor. That part is cut out as you see in the photo. The rest fyi is the wood came from a spool of rope. The two sides of wood I kept and discarding the cardboard center supplied me with 6 ea of pie sections of wood. Reinforced by coating the wood with resorcinol glue and then rattle can paint.

Some have specifically made devices to spread the metal to have room for gear or pulley on rear wheel. I can say that I had tried some of that, but as well I welded reinforcement metal on and then notched out just required space when I bought a manufactured sheave meant to mount to spokes. It required more space as it was a little wider. Adding the metal first meant less warp from weld heat, besides replacing loss metal from the notching.

https://motorbicycling.com/attachments/img05714-20111110-1716-jpg.42032/

My first thread where motorbike plans to become art vehicle... still may have that done

https://motorbicycling.com/threads/...bike-diyer-build-to-add-side-car-maybe.29678/

Thread on trail bike and video on vimeo of a ride out there

https://motorbicycling.com/threads/mendicino-national-forest-trail-riding.54926/

http://vimeo.com/117886338
 
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Ruff idea of how I'm gonna mount the bolans. The angle iron will bolt right to the frame and then be welded. On the bottom of the engine i'm making a plate that will bolt to the engine and frame the same way the top mounts. The frame has been flattened in a spot to clear the flywheel. And it appears the pulleys will line up perfectly.
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I'll loose the ability to pedal but with a belt tension clutch I could just take the tension off the belt and wrap a rope around the flywheel like I have been doing.
 
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The rear pulley fits inside the frame without bending the frame. I have the pulley drying with jb weld to the hub so I can let the jb weld harden make sure the pulley is true and then weld the pulley to the hub from the back.
 
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If the pulleys line up well enough and I can figure out a belt clutch before the engine is completely welded in place then I can probably make this work.
 
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Or hang it on the wall in the garage and have a neat looking belt drive bike? The engine revs really high so it should have no trouble pulling me around. If I can get it together to that point is the question.
 
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sorry about the terrible photo but anyways the pulley is welded to he hub. I didn't get it completely straight like the front pulley but it should be ok I hope. The pulley on the bike clears the frame. And both pulleys line up nicely. I may have to chop and re-rout a part of the frame so the belt has the needed space but that is easily done. Maybe tomorrow I'll find the tiny pulley I have laying around and work on the tensioner..
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Well it's that part of the day when all the work is finished and I have time to waste.. Gonna go look for a belt in the shed. So I can check and make adjustments for the belt to fit around both pulleys. And with the small pulley I have and a couple small pieces of metal a tensioner should be simple enough.
 
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Aug 8, 2019
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Gonna go work on the bottom mount and I have been thinking of ways to get some more power out of the 31cc seen people bolts these tuned pipes on leaf blowers and it's most likely better then the junk muffler on it now.
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cannonball2

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You haven’t listed the large pulley size but If I am seeing correctly the gearing would be way too tall. Most small displacement 2strokes are used with friction drive to obtain a ratio that allows the engine to rev into its power band which is usually quite high. That combo you have would probably work a larger 4stroke pretty hard. I have never built a belt drive trimmer based build so can’t speak to what ratio it would require but am guessing something around 30:1. Depends on wheel size of course. Cool thing about friction drives as it drives any size wheel the same for a given roller size, 26” or 10” it’s all the same.
 

5-7HEAVEN

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Aug 2, 2008
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Totally agree with cannonball2. Without knowing the pulleys' diameters, I'd say your gear ratio's less than 3:1. You need about 20:1. If you have a clutch, your lack of gearing will disintegrate it.
Without 2 pairs of pulleys or sprockets (4 total), it won't work.

My bike's engine sprocket has 11 teeth. It's connected to a 72t gear, giving 6.55:1 gearing. The engine has a 5:1 gearbox, resulting in 32.72:1 gearing. Without the gearbox, my engine's clutch would burn up, and my bike wouldn't move an inch.

You need to hook up at least 2 sets of pulleys for your engine to pull your bike.
 

5-7HEAVEN

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If you're willing to give up pedaling, you could use the bottom bracket as a left-sided jackshaft.
You'd need a 1" engine pulley and a 6" pulley at the bottom bracket. Then a 3" pulley at the bottom bracket and a 12" pulley at the back wheel. Or something to that effect.

6/1 = 6. 12/3 = 4. 6 x 4 = 24:1 gear ratio, which would make your engine buzz and your bike fly!