any sheave that can accommodate two belts?

[grinningremlin]

I don't know how you plan on doing two sheaves, front wheel/all wheel drive?A moving/sliding dual pulley might work, belt alignment is pretty important, as the pics show, it's tight.
One thing, you'll need to buy (or make) that little tool that snaps the sheave on the spokes, it's real hard not to bend the spokes taking the sheave off, the bigger/thicker the spokes the harder it gets, just a caveat.

 

[butterbean]

Any reason a second belt can't ride on the flat part of the sheave?

 

[grinningremlin]

It's flat but it's angled top and bottom in a triangle toward the spokes/hub.If you could mount it, use the rear wheel as a lathe with a chisel/dremel or the like to grind a flat,... maybe, but I think you'd start weakening the sheave at that point.

 

[butterbean]

I don't have many options if I want to run two belts, unless I use a second 26" rim as a sheave and find the appropriate size pulleys for the amount of reduction I need.

 

[butterbean]

That won't work either. A sheave the same size as my wheel will make it impossible to use an idler clutch. I'm really stuck, but really determined to make some kind of two speed setup.

 

[butterbean]

This may end up having to stay as a single speed. I still want to convert to belt drive though, and may end up ordering a Whizzer sheave from Taiwan for $69 shipped.

 

[butterbean]

I may have found a variable pulley, but the description is confusing. Here is a link: www.mcmaster.com/#6568k1/=ql1hdm.

 

[butterbean]

I was able to confirm that the pulley I linked to in my above post is indeed a variable pulley. I will be ordering it very soon.

 

[BigBlue]

If you sit tight, Whizzer Paul will list again. I've been watching his listings for a while on Ebay. Almost bought one of his manual clutches for a future project.

That pulley listed at McMaster-Carr doesn't have enough spring tension. Your belt is going to slip. Those pulleys/variable sheaves are made for fractional horsepower electric motors. It's hard to find the specs on those pulleys/sheaves. Looking at Wayne Z's post on the other forum that is why he went with a heavy rear suspension shock spring to replace the stock spring.

More appropriate variable pulley/sheave for a MB application would be a Lovejoy 6030. It is rated for 3hp at 1700 rpm. The spring tension is rated at 108 inch-pounds of torque. At $181 it is priced too much for most peoples MB budgets. Installation would be another issue.

I wished the Comet 20 Series driven could use a regular v-belt because it would probably have the correct spring tension to run with a centrifugal clutch and a manual belt tensioner. Unfortunately they use a 3/4" wide belt.

I hope you can sort through the issues. I am looking for ideas for future builds.

Chris
AKA: BigBlue

 

[butterbean]

If belt tension is an issue, I can find a stiffer spring, that's no biggie. Whizzerpaul is out of town until the 22nd, I will wait until then to order a sheave. I think with the right idler setup, the belt might not slip. I was thinking of attaching a stiff spring to the top chainstay to maintain tension. It might work better than my current setup, with the spring attached to the bottom chainstay, and a stiff enough spring should maintain tension. With the idler tension spring and the cable controlling the pivot arm both pulling in the same direction, should get pretty even tension. If the idler can apply even tension through the range of the pulley's movement, ought not to be any problems.