RE-Inventing the CVT

Yes, I have used one. The transmission company I worked for purchased one when they first came out to test the technology. (Fallbrook has a joint-venture with a tractor company for an agricultural applicaiton.)

In the bicycle application it works great. The transition through the ratios is seamless and smooth. It is by far the best method to transfer power on a bicycle that I have tried. The only downside is weight. If I remember correctly the hub weighs ~2.5 lbs.


Tony,

The axis is not important but it is the means to what is. The important factor is how far away from the axis the disk contacts the ball. The greater the difference in contact points of the two disks the greater the speed differential. When the disks contact at the same radius the is a 1 to 1 ratio. If you turn axis one way you will get a ratio less than 1, and the other way the ratio will be greater than 1. You go from an underdrive to an overdrive ratio.

 

Look at the lines next to Ri, Ro - they're indicating radius of input, radius of output. The first picture is equivalent to having a small gear on the input engaged with a large gear on the output; the second is 1:1 because the radii are the same; the third is similar to a large input gear and small output gear.

I'm not sure this would be able to bear very much torque, though.

 

130 newton-meters at the hub, according to the data sheet (96 ft-lb). I guess that'd do for a bicycle under most conditions. 350% ratio range. But nearly 4 kg? That seems like a lot. I guess it includes the mounting hardware and the grip shift controller. But no freewheel or cogs. Cool idea!

-Chap

 

An HSD sized for a bicycle would be smaller than a tuna can, and you could get electric assist along with it. And no chain.

 

If the plates contact the balls in the same spot, the transfer is one to one. When the plates aren't equal, neither is the transfer. Maybe if I think about it longer, I'll be able to come up with a simpler answer.

There are some really cool advancements in bicycle technology lately, this being one of them.

 

Kind of a neat arrangement for fully variable gear arrangement, but I would think that the working transmission fluid would get pretty hot with any significant level of power transmission through this device, simply due to frictional forces. Though they do claim scalability for it.

 

It is a scaleable technology. The company I worked for was worried about Infinitrak, a joint venture between MTD and Torotrak. (I had the wrong company, Torotrak uses the same technology has Fallbrook except they use a disk with a curved perimeter instead of a full sphere to get around Fallbrook's patents.) Infinitrak started production in 2007 for the 2008 model year Cub Cadet I-Series. Now the Cub Cadet is back to tried and true hydrostatic transaxles but the Infinitrak is still used in the Craftsman Revolution. (Twin of I-Seris)



Here is a pretty good demonstration video for the a zero-turn mower application: hq_ttt_anim