Flat belt drives?

[dequinox]

I was brainstorming stupid ideas for ebike non-hub drives, and came across an interesting woodworker's channel... Matthias Wandel (engineer turned woodworker, or visa versa...). This fellow has build a plethora of wooden machinery, but among his creations is this flat-belt driven wooden bandsaw. I'm wondering if this might work for an ebike drive for those of us looking to scrap together an odd-ball mid-drive?

 

[Solcar]

Some of my early ideas for low power ebike drive involved using a vacuum cleaner belt in the first reduction stage. An advantage I see with it is that it is quiet. Another plus is low cost. Also, there is convenience in being able to buy a part from the department store.

 

[Punx0r]

A flat belt will be several times the width of the common synchronous (timing/toothed) belts to transmit the same power.

 

[ferret]

I believe a flat belt will have to be highly tensioned to avoid slippage which will cause more drag and less efficiency.

Avner.

 

[spinningmagnets]

Theres a type of belt used on modern automobile alternators and also on vacuum cleaners/washing machines/etc...called "poly-V"

By having a thin belt, you can package a large reduction in a small space because the belt can bend around a very small drive pulley. But...a smooth belt would clearly have low adhesion to the smooth drive pulley, so...first you make the belt as wide as will fit, and second...the distinctive method chosen to increase the rubber-to-metal contact was to add a series of small V-grooves on the contact surfaces of the belts and pulleys.

I don't think these would work for high-powered systems, but for a lower-powered system, I think it might work fine. I believe the Miele Evox uses this.

 

[dequinox]

Poly-V's suffer a little in the efficiency department, but yes I've heard of them. The point of a flat belt would be that making components for it would be CHEAP... as long as you could get enough grip without having to overbuild the tensioning components. You can even buy flat belt pulleys at places like sdp-si. I think it would be interesting to try it some time... just wanted to hear some thoughts before I go at it!

 

[Punx0r]

Poly-Vee are also quite a lot wider than a synchronous belt

 

[amberwolf]

I used a poly-v from a treadmill in one of my reduction stages in the first version of CrazyBike, and the abandoned ReCycle before it, but it was never road-tested as I got the easier-to-use powerchair motors at that time, and never finished that version of bike to test it.

Based on the limited bench testing I did with it, if you were using higher RPMs but lower torque on that stage of drive, it would probably be ok, but with higher torque it might not (slippage under load, unless tensioned so high it would wear quickly and add a lot of drag).

What documentation I did on that, pics, etc, should still be on my old http://electricle.blogspot.com project blog (before I found ES, I think).

I've wanted fora long time to go back and see if that would work or not, but I don't know that Ieven still have the parts for it, after the mess after the housefire.

 

[dequinox]

I may have to work up some sort of bench test for this one day. I have been thinking of doing a wooden e-bike and thought it wood (not sorry) be pleasing to the eye to have most of the drive components be made from wood as well.

 

[JayCee]

I think you'd be far better served by using a lawn tractor v-belt (like on a mower deck) running simple pulleys. V-belts are really cheap, last well, and can transmit a few HP like nothing (typical mower deck easily sucks up 5-8HP) - they don't even have to be tight. 1/2"x36" should be in the ballpark - http://www.sjmparts.com/belts/belts-true-blue?page=4