On Mar 19, 2:21*pm, "Wild_Bill" wrote:
Having the motor mounted to the axle appears to be a very poor design, to
me.
There are losses with a drive shaft, but the motor doesn't need to withstand
the physical motion of following the axle.

This method of differential drive would be entirely suitable for a small
vehicle that always runs on smoooth or gradually changing surfaces, but
hardly seems intelligent for a (large) car in everyday driving conditions..
A large car wouldn't become a lot lighter by removal of the engine and
transmission, since a considerable amount of space would likely be used for
batteries.

The extreme forces that the motor would need to withstand in real-world
conditions.. potholes, abrupt impacts of road debris etc, would be applied
as shock loads to the rotational power from the motor, with only the drive
belt to absorb such rotational shocks (by the looks of it).

Shaking and jarring the rotating motor components would likely result in
serious inefficiencies in the application of the horizontally-oriented motor
shaft power, IMO.

If the axle-mounted motor were allowed to float by a dampening
mechanism/swing arm-design the power could possibly be applied more smoothly
and likely more efficiently.
WB

The choice is a compromise between the simplicity and reliability of
wheel motors and the improved handling at higher speeds with less
unsprung weight. U joints are still the weakest link in a driveline.
http://en.wikipedia.org/wiki/Automobile_handling

A fast vehicle with in-wheel motors would lose steering control due to
wheel hop before vibration damaged the motor. My suspensionless garden
tractor is barely steerable on trails at top speed, I slide it like a
dirt bike.

jsw