In message , The Natural Philosopher
writes
Andy Champ wrote:
On 18/09/2012 19:27, The Natural Philosopher wrote:

Motors in hub are an extremely bad thing. Adds to unsprung weight.
http://en.wikipedia.org/wiki/Unsprung_weight

Not if the motors weigh less than the axles they replace.
I'm more likely to believe you than some. Is this really possible?


yes.

Not cheap - Neodymium magnets and enough silicon iron in the stator..

http://www.hobbyking.com/hobbycity/s...Aerodrive_SK3_
6374_149kv_Brushless_Outrunner_Motor.html

is running at about 5bhp per kg.you probably need about 20bhp per wheel
for a small car (80bhp AWD). Which is 4kg per wheel. That's probably
about the same as an axle hub and CV joint.

Its definitely better weight wise to use a motor per wheel and dump the
differential as well.

There was a combination motor I once came across, *steromotor*?

I forget the application but the rotor was attracted to the rotating
stator field and able to *roll* rather than rotate. The actual shaft
speed was a function of the air gap dimension.

Lots of vibration and very low speed!

--
Tim Lamb