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...ner_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.

The problem with an inboard motor is you need the CV joints (or a
dreadful swinging axle) as well. Those add weight and cost.

Plus you get better packaging with in wheel motors.

Biggest problem is you probably can't gear it - except with more in
wheel weight like an epicylic box. So it needs a LOT of poles to get the
actual torque you need. AND you need flexible and pretty substantial
cables as well

But overall I think that the best way to package a leccy car from a
'blank sheet' is battery under the floor to keep weight down low and
extending right into the axle regions, and a motor on each wheel.
The battery is far and away the heaviest thing so you want it low and in
the car model. The means you probably don't want transmission there at all.

Bernie Ecclestone has announce a 'Formula E' series for all electric
racing. It will be fascinating to follow. And see what they end up with
by way of battery swapping and getting performance out of the cars.

http://www.bbc.co.uk/news/business-19402383


I'd want to stick the motors _and_ the brakes inboard on drive shafts.
But I know I'm old fashioned...

Andy


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.