Saturday, April 25, 2009

30> Active Wheels

Back in my January 30 post, I brought up the concept of the “motor in the wheel” design. I like the idea a lot because it has no more moving parts than a LIM (linear Induction Motor) but is all contained in a neat little package, as opposed to having to provide miles of “reactor plate” in the track. Also, the tolerance between the rotor and stator parts of the motor can be very small. With a LIM these spaces would be a challenge to maintain, effecting efficiency. Check out this excellent simulation by Paul Nylander (http://bugman


Oops. Bloggers' videos don't loop so it doesn't go 'round- Check out the web site...There's lots of neat stuff..

I found motor in wheel suppliers for bicycle conversions, and conveyor belts (drum motors) but I missed the obvious search words “wheel motor” until I ran into this interesting innovation from Michelin.

Anyway, I found a UK company, PML that produces a range of “wheel motors” sized for vehicle use. I have not had a chance to consider the various choices or to work them into a design, but they appear to be sufficiently small as to enable the many wheel, split carriage design I favor. (lots of traction, very tight turning radii, both up and down and side to side)

Designs will be forthcoming.


Mr_Grant said...

A wheel motor is still a rotary motor, and the occasional need to brake on a wet surface still limits headway and therefore capacity. In ULTra I think it's about 2 seconds -- at 25 mph that's... 73ft?

Dan said...

Dan The Blogger Responds-
Hello, Mr. Grant – I have to say I don’t much like the Ultra 1 design. I just can’t see it changing any cities in a substantial way. It looks fine as a baby step, like for campuses or medical centers. It looks like it would have big problems in a snowstorm. I agree that LIMS don’t have traction problems of any kind, but they can’t be very efficient without finding a way to close the gap between LIM and reactor plate to a space that is comparable to a rotary motor. Also the stator of a rotary motor has magnets and the LIM has to induce that magnetism. That doesn’t sound efficient to me. The Baldor LIMs cannot even lift half their own weight on a continuous basis without special cooling equipment. I will note that PRT international’s current design uses some tweaks that may or may not be readily commercially available.
(They also mention how its mounting position affects the vehicle’s center of gravity, testimony to the fact that LIMS are very heavy.) Last but not least, I would note that the reactor plate on a LIM system, being roughly analogous to the stator (though much heavier) on a rotary motor is shared. If there is constant traffic, not carrying around a stator might make some sense. If the object, however, is to create a less expensive more comprehensive network, the idea of including miles and tons of “stator” to the track seems like a bad trade-off for increased traction. And, of course, my design doesn’t get wet anyway.