CVT Full Suspension CVT

[loquin]

Cool.

I was looking at Lovejoy CV drives (industrial versions of that CVT) yesterday. One of their options is to have a fixed pulley size on the drive end, and the spring-loaded pulley sheave at the driven end. To adjust the ratio, you simply move the drive pulley closer of farther from the driven end... the spring takes up any slack, and the ratio changes (larger reduction when you move the drive pulley towards the driven sheave.) The ratio range isn't as great as when you have sheaves moving at both ends, but, it's in the 80 percent range.

I believe you could get the same effect (if/when the CVT drive sheave dies) by replacing the drive sheave with a fixed pulley (same size as the sheave is currently at greatest reduction ratio) and adding an idler pulley inside the CVT belt, and moving it out (or in,) to tighten/loosen the belt. When the belt tightens, it would cause the driven sheave to widen out, and the ratio to decrease. In effect, you would have a manual shifting CVT...

 

[kerf]

Cool.

I was looking at Lovejoy CV drives (industrial versions of that CVT) yesterday. One of their options is to have a fixed pulley size on the drive end, and the spring-loaded pulley sheave at the driven end. To adjust the ratio, you simply move the drive pulley closer of farther from the driven end... the spring takes up any slack, and the ratio changes (larger reduction when you move the drive pulley towards the driven sheave.) The ratio range isn't as great as when you have sheaves moving at both ends, but, it's in the 80 percent range.

I believe you could get the same effect (if/when the CVT drive sheave dies) by replacing the drive sheave with a fixed pulley (same size as the sheave is currently at greatest reduction ratio) and adding an idler pulley inside the CVT belt, and moving it out (or in,) to tighten/loosen the belt. When the belt tightens, it would cause the driven sheave to widen out, and the ratio to decrease. In effect, you would have a manual shifting CVT...

That was my backup plan if I couldn't repair the variator. Wasn't looking forward to beginning the engineering process all over again so soon, wasn't looking forward to the wifes reaction either. I don't know if the Shimano push button shifter could handle the load of the idler against the spring sheave but it would have been an interesting challenge.

 

[curtisfox]

This may sound like a stupid question, but how would it work to ( have not taken mine apart yet ) eliminate the gear box and drive just off the shaft comeing out it? As long as I have the proper gearing like 18:1 to the rear wheel.

 

[loquin]

It probably could be done, curtisfox - You'll probably need to get a new shaft machined to extend out through the existing gearbox case, you'd want to add a supporting bearing out past the gearbox (possibly bolting it to the gearbox cover,) and you would need to reverse the engine direction, as the existing gearbox reverses rotation.

 

[kerf]

I would leave everything except the variator. To the variator shaft I would mount a fixed sheave (don't know how it would be keyed) and a spring loaded idler. The idler would be manipulated via a cable attached to the rear dérailleur push button shifter. All of this is very general and there would be much to learn.

 

[loquin]

Yes, that's how I would make a manual 'shifting' CVT, kerf. I was replying to curtisfox's question about bypassing the gearbox...

 

[machiasmort]

Mind blowing! Excellent job Kerf!

 

[curtisfox]

It probably could be done, curtisfox - You'll probably need to get a new shaft machined to extend out through the existing gearbox case, you'd want to add a supporting bearing out past the gearbox (possibly bolting it to the gearbox cover,) and you would need to reverse the engine direction, as the existing gearbox reverses rotation.

THANKS I just wanted a second opinion. I can machine a shaft if needed.I am a old timer like the engine on the right. Besides I was thinking a belt to run to the rear wheel Wizzer style. I am working on a Shaw clone and not sure what engine to run yet. Sure would be nice to find a engine that looks like the old 2 cycles....Curt

 

[kerf]

Since I've been busy, I haven't ridden in about three weeks, until this past Sunday. Ride went great but I noticed some belt slippage on the way back home, keep in mind the bike was a little oily from previous runs. Yesterday, I pulled down the tranny to see what was up and found the variator just like I left it but there was a light oil film on the belt and sheaves. That's when I noticed engine oil, from the exhaust all over the back side of the tranny. I had drilled 4 1" holes into the front and back edge of the belt cover for cooling and it looks like the back draft has been pulling exhaust oil into the back edge holes. I cleaned up everything with brake parts cleaner and applied aluminum tape to the vent holes on the back side of the cover.

A quick test ride confirmed that there was no slippage and everything is back to normal. Want to take her for an extended ride Sunday morning but it's going to be cold, down to 34 degrees. Time for the arctic gear I guess.

 

[curtisfox]

Have you ever seen the Varidrive pully out of a lawn tractor? The center web moves back and forth and changes speed. I haven't seen one used on a motor bike probable because its big, but I don't know why it can't be made smaller like useing the CVT pullys or the like. I have a John Deer 110 veridrive pully there is nothing to them no springs or anything to go wrong with just the center web moves?........Curt