On Saturday, 17 February 2018 06:38:06 UTC, Johnny B Good wrote:
On Fri, 16 Feb 2018 12:18:25 -0800, tabbypurr wrote:
On Friday, 16 February 2018 18:39:21 UTC, Tim+ wrote:
Johnny B Good wrote:
Additionally, €śmotor in hub€ť adds hugely to unsprung weight (which
isnt supposed to be a good thing). I appreciate that this might be
mitigated by the use of rare earth magnet motors but that brings us
back to the environmental problems again.
As Im sure you know, €śrare earth elements€ť arent actually rare, just
fecking difficult, dirty and expensive to extract.
https://e360.yale.edu/features/
boom_in_mining_rare_earths_poses_mounting_toxic_ri sks
Tim
unsprung mass kills road holding.
You could always use 2 inboard motors rather than 4 in wheels.
I deliberately made the caveat about their unsuitability for high
performance road cars on account of the 'unsprung mass' issue but I feel
that a fully integrated hub motor will weigh little more than the steel
wheels currently used by most saloon cars today (and may possibly prove
to be slightly lighter through the use of suitable materials).
the wheels are still required. A low speed motor must necessarily be large, and that means a lot more weight than the wheels. The resulting heaviness is unsuitable for ordinary road holding performance.
They'd be a horrible compromise for a high performance car but most
no, they're not be compatible with high performance at all
likely a more than acceptable compromise for a 'standard electric road'
car, considering the elimination of the weight and expense of a klunky
space consuming mechanical transmission system.
they'd increase unsprung weight greatly. Good enough for a low speed bus.
A fully developed active energy recovery suspension system could
ultimately overcome this problem of 'unsprung mass'.
it can't
It's also worth
remembering that the suspension components themselves (spring, damper and
drive shaft on each driven wheel) form a part of this 'unsprung mass'.
suspension can't be eliminated
Also, let's not forget the mass of the disk brake assemblies which, with
regenerative braking, can be reduced in size thus offering yet a further
reduction in 'unsprung mass'.
not really, the friction brakes still need to stop the car from top speed.
This latter weigh saving would require an emergency electric backup in
the event that the normal regenerative braking system suffers a failure
you can't back up a safe braking system with an inherently unsafe one
that could result in burning out the downsized disk brakes on a long and
steep descent.
that's easy to work around with electronics. Use regenerative braking. Also monitor brake temp, and warn then stop the car if too hot.
NT
I'm sure such risks can ultimately be addressed if given
sufficient thought and development. :-)