Re: put the motor in the wheel

[John Paramore <wizprodj@eskimo.com>]

On Sun, 30 Aug 1998 soisland@gte.net wrote:

> why do you never see a commercial car with in hub drive, are they too
> expensive,  not mechanical sound,  engineered bad ??? In Sunrayce EV it
> seems only a few do it.


When you but a lot of weight at the hub it adds to the mass/momentum that
the springs and shocks have to control, and affects handling adversely.

To set up an example, imagine you're holding a threaded bar. Wave it
around and note that it's pretty controllable. Now add a ten pound weight
to the end of the bar and wave that around. You'll discover that the bar
has now become very hard to control because the extra mass at the end,
once in motion is hard to overcome.

In the average vehicle, simple tire rebound provides plenty of energy for
the springs and shocks to overcome. adding unsprung weight in the form of
a hub motor dramatically worsens handling.

Many race cars are designed to minimize unsprung weight by placing
components such as brake calipers and rotors inboard attached to the
sprung weight of the chassis, and connecting them to the wheels via short
driveshafts, and you could do the same thing with motors.

John