I have a 79cc Predator and an agk jackshaft. First, let me say the rear wheel is using a moped hub and 11g spokes, so should be able to handle a good amount of torque and horsepower. So here is my idea. Instead of using the standard 11t maxtorque clutch, I could use a clutch with a belt pulley or even perhaps just swap out the toothed gear on my existing clutch for a pulley, I know they sell replacement pulleys for maxtorque clutches, just not sure if its a direct swap or not. Then I would remove the toothed input gear from the jackshaft and swap it out for a variable pitch pulley, the kind you twist manually to adjust, but instead of actually having to twist the pulley itself by hand, devise some sort of mechanism whereby the pulley could be adjusted via a handlebar lever? Does anyone think this is possible? Anyone have any suggestions on how to devise a shifting mechanism for the variable pulley? As far as to why I want a manually shifting belt drive, belt is quiet and a bike really only needs 3 speeds, medium speed for cruising, low speed for climbing and high speed for getting out of a jam quick. Any thoughts will be appreciated.
Converting agk jackshaft to manually shifting belt drive?
- Thread starter dtv5403
- Start date
Using one of those pulleys is not going to work to manually shift. They vary the OD by loosening the setscrew and turning one sheave around a threaded portion to vary the distance between sheaves. Making this manually operated would be a stretch - even if you did devise a way to separate the linkage from the spinning motion, you'd still be fighting the torque of the belt friction on the moving sheave. Also, changing the ratio requires multiple revolutions on the threads, so you'd need some sort of electric motor that spins it to make it move for faster shifts. And then you'd have to figure how to tension the belt to adjust to the size differences.
The better movement is by way of the CVT, in which the moving sheave slides axially along the crankshaft and is not affected by belt friction.
If you want different gears, I would recommend one of two things. Get a comet CVT and devise a way to shift the drive pulley manually. The tension problem/"total tooth count" would already be solved with the moving driven pulley.
Best option: make a belt clutch and use a multi-speed internal gear hub to handle your shifting. Preferably the S3X fixie hub so you can use engine braking to slow it down. The little predator probably won't destroy it soon like a bigger motor, so you'd be alright.
Here is my bike with belt clutch, then with MaxTorque clutch. The belt clutch worked well. You need a belt guide pin to make sure the belt fully disengages the drive pulley. I got away with one, on the top side just behind the drive pulley. The spring pulls it to the drive position and a lever on the handlebar pulls it to disengage, just like a real clutch. Front pulley 2", rear 7", 1.312" ball bearing for tensioning.
I don't like the MT auto and am waiting on parts to convert to CVT. I liked how the belt clutch hooked up but it isn't legal in CA. Bikes need to have an automatic transmission.
The better movement is by way of the CVT, in which the moving sheave slides axially along the crankshaft and is not affected by belt friction.
If you want different gears, I would recommend one of two things. Get a comet CVT and devise a way to shift the drive pulley manually. The tension problem/"total tooth count" would already be solved with the moving driven pulley.
Best option: make a belt clutch and use a multi-speed internal gear hub to handle your shifting. Preferably the S3X fixie hub so you can use engine braking to slow it down. The little predator probably won't destroy it soon like a bigger motor, so you'd be alright.
Here is my bike with belt clutch, then with MaxTorque clutch. The belt clutch worked well. You need a belt guide pin to make sure the belt fully disengages the drive pulley. I got away with one, on the top side just behind the drive pulley. The spring pulls it to the drive position and a lever on the handlebar pulls it to disengage, just like a real clutch. Front pulley 2", rear 7", 1.312" ball bearing for tensioning.
I don't like the MT auto and am waiting on parts to convert to CVT. I liked how the belt clutch hooked up but it isn't legal in CA. Bikes need to have an automatic transmission.
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I'm going to run the setup I have, and see how I like it. If I have problems, my first step will be upgrading the clutch. I currently have a Max torque six shoe clutch, and I've tuned it the best I can, black spring and alternating heavy and light shoes, so engagement will be a little higher than whatever the clutch is tuned for stock. Anyway, Max torque makes a better clutch called the Draggin Skin, and it has stamped metal shoes and comes with 4 sets of weights and 3 springs, allowing tuning of the engagement speed from 2850 to 3800 rpms. So we'll see how things go.
Manual shifting belt drive. Has been working great for a few years.
http://motorbicycling.com/showthread.php?t=44397
http://motorbicycling.com/showthread.php?t=44397
I have been pondering this for awhile now, and I have a couple options for you.
The variable speed pulleys are expensive, but you could make one yourself using a less expensive variable pitch pulley like you described.
You could grind the threads off of the pulley, and replace the threads with a spring, and some sort of retaining collar.
The other idea would be to use a vari drive pulley like they use in riding lawnmowers.
This would require you replace the final drive with a belt too.
The variable speed pulleys are expensive, but you could make one yourself using a less expensive variable pitch pulley like you described.
You could grind the threads off of the pulley, and replace the threads with a spring, and some sort of retaining collar.
The other idea would be to use a vari drive pulley like they use in riding lawnmowers.
This would require you replace the final drive with a belt too.
