how to advice needed - friction drive

brucemg51

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Jul 10, 2008
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I am so thoroughly disgusted :-|| with those chinese chains and sprockets that I can't stand the thought of another build with them. Here's my idea. A 42cc chain saw engine. I've gotten lots of mounting ideas. My question right now is how to attach a drive roller onto the drive shaft of the engine. Centrifugal clutch and pull starter looks real appealing. That drum sanding drill attachment I thought would make a great friction roller, but how to attach it?
 

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deacon

minor bike philosopher
Jan 15, 2008
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north carolina
I cant help you I took my clutch off my chainsaw. I attached my drive directly to the drive shaft of the engine. I use a gravity clutch which is no more than raising and lowering the engine.

I agree about the china bike by the way it's why I got interested in the diy friction drives.

How about welding a sleeve over the drum sander's shaft then welding the sleeve to the clutch drive gear.
 

brucemg51

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Jul 10, 2008
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I cant help you I took my clutch off my chainsaw. I attached my drive directly to the drive shaft of the engine. I use a gravity clutch which is no more than raising and lowering the engine.

I agree about the china bike by the way it's why I got interested in the diy friction drives.

How about welding a sleeve over the drum sander's shaft then welding the sleeve to the clutch drive gear.
So you're saying an alternative would be to remove the centrifugal clutch and attach the roller directly to the engine's drive shaft? Then, by using a lever and cable you could lower the engine onto the tire after you got pedaling along. I think I've seen that done somewhere. Question: wouldn't that leave just the weight of engine pressing down to make contact with the tire and would that be enough to prevent slippage? What I've seen is using a quick disconnect and slotted supports to raise or lower the engine. That way you can force the engine down onto the tire with some pressure, then lock it in place.
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
For that you use a door spring. You need some extra tension for sure. The spring also stabilizes the engine on bumps ect. You need the spring on something like it even with a centrifugal clutch.

To be honest I don't know who strong a chainsaw clutch is. With a chainsaw you would still have your rope start since it is on the other end of the drive shaft. A chainsaw is pretty heavy but I rode mine today.

I lever it down then tie if off to start it. When I am seated I pull the brake lever clutch and release the tie off loop. then when I am moving I slowly lower the drive onto the tire.
 

comfortableshoes

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Jul 22, 2008
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Beverly, MA USA
I used to use a slotted bracket for mine, but THAT leaves a lot of pressure on the drive roller and however it attaches. When I did that I sheared off an attachment. It sucked to pedal home. Now I use a heavy door spring and a item I can't for the life of me remember the name of to perfect the tension. When I hit a bump, the spring allows the engine to move with the tire- no more broken shafts.

Even if I went back to using a clutch on either of my engines I would use the spring tensioner- it just seems more forgiving for the engine.
 

brucemg51

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Jul 10, 2008
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I used to use a slotted bracket for mine, but THAT leaves a lot of pressure on the drive roller and however it attaches. When I did that I sheared off an attachment. It sucked to pedal home. Now I use a heavy door spring and a item I can't for the life of me remember the name of to perfect the tension. When I hit a bump, the spring allows the engine to move with the tire- no more broken shafts.

Even if I went back to using a clutch on either of my engines I would use the spring tensioner- it just seems more forgiving for the engine.
I'm guessing you mean that if you lock the engine down rigidly with slotted mounts, it can't move with the bumps, which it could with springs and turnbuckles.
 

deacon

minor bike philosopher
Jan 15, 2008
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north carolina
I think I am going to go to the hardware store today and buy some shorter springs and a couple of small turnbuckles. That amount of control on the tension is something I have never had.

thanks for the information that slipped in almost by accident. Actually I think I'll just but the small turnbuckles I can cut my springs in half.
 

Egor

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Jan 30, 2008
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Hurricane Utah
This is how I did it. The lever is the spring, as it is long enough to flex. I pull the lever and it puts the engine down on the wheel. It is accessible from the riding position so I can start and stop the engine while riding. I put a small fastener in the frame to hang the lever on in go position. I would try and use the clutch if you can, it will need support on the outside of the roller. Have fun, Dave
 

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geeksquid

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Feb 14, 2008
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This is how I did it. The lever is the spring, as it is long enough to flex. I pull the lever and it puts the engine down on the wheel. It is accessible from the riding position so I can start and stop the engine while riding. I put a small fastener in the frame to hang the lever on in go position. I would try and use the clutch if you can, it will need support on the outside of the roller. Have fun, Dave
But I've always wondered if the clutch on a chainsaw is strong enough for the load of a rider. It seems they would be a lot less hefty than regular mini-bike/go-kart clutches.
 

geeksquid

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Feb 14, 2008
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I'm guessing you mean that if you lock the engine down rigidly with slotted mounts, it can't move with the bumps, which it could with springs and turnbuckles.
If you mount a motor to the frame and the motor mount is welded or bolted to the frame and can't move, well, the tire is also mounted to the frame and can't move, so how would the motor/drive roller be affected by bumps? I would think that only a foreign object like a rock would be the only thing that could affect the motor's contact with the tire and even then, the tire would give enough to not affect it except for a short, quick bump depending on the size of the rock. But I know you have to have to be able to engage and disengage it but it still seems everything should stay in place on bumps.