The supposed space savings is very much in the mind of the executive
that funds a hub wheel endeavor. It turns out not to really save much
space, unfortunately.
The gear losses are about 7%, give or take, when you use a gear
reduction to centrally mount a small high-speed electric motor. When
you use a gear box, the motor/gearbox combination becomes much
smaller and cheaper than the direct drive hub motor. This is because
the torque of the motor is directly proportional to the size and the
cost. Speed (rpm) has little influence on the cost of a motor. A
gearbox thus greatly reduces the cost and makes the motor/gearbox
combination smaller, so there really, in the end, is not much space saving.
The trouble is, one cannot completely solve all of the innate
problems of an in-wheel motor in a highway capable vehicle. At least
not economically for most of the problems and for the other problems
perhaps not at all. This is what every major car manufacturer has
independently confirmed.
The very first attempt was by Porshe in the late 1800's.
http://press.porsche.com/news/release.php?id=642
It was not really highway capable, however, as its top speed was 22 mph.
I could go on and on. (I have done so before. Look it up in the
archives.) Hub motor vehicle prototypes die the "death of a thousand
cuts". It is not just one problem, but many subtile, very serious,
issues. Each takes its toll to eventually kill the production vehicle.
I should note that for low speed vehicles and for racing vehicles,
hub motors and individual wheel motors can sometimes make a lot of
sense. Often for these specific applications, the problems fade away
and the advantages can win out.
Bill D.
At 09:55 AM 12/24/2013, you wrote:
Let's say one could solve the problems of an in-wheel motor. Then, how much
advantage would it have over using some sort of transxle and mounting the
motor the chassis a little inwards from the wheel area.
The only advantages I can think of are:
- slightly less space used since the motor would be almost completely in the
wheel well area,
- ever so slightly less weight and resistive loss (no transaxle).
Peri
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Bill Dube
Sent: 24 December, 2013 7:44 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] VW Bora will have Protean in-wheel motors
I agree. Every car manufacturer has boldly announced in-wheel motors,
built a prototype, and then made an embarrassing retraction.
Sounds like a terrific idea, then they build one and learn for
themselves the insurmountable safety issues of highway driving
(uncommanded asymmetric torque, unacceptable unsprung weight, etc.),
then as quietly as possible they bury all the prototypes and pretend it
never happened.
I wish they would publish a book or report on the bad experience, but I
guess it is just too embarrassing.
Bill Dube'
On 12/23/2013 9:28 PM, Al wrote:
> Sigh, in-wheel motors, again, when will they learn.
>
> ----- Original Message ----- From: "brucedp5" <[email protected]>
> To: <[email protected]>
> Sent: Monday, December 23, 2013 8:11 AM
> Subject: [EVDL] EVLN: VW Bora will have Protean in-wheel motors
>
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA
> (http://groups.yahoo.com/group/NEDRA)
>
>
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
For EV drag racing discussion, please use NEDRA
(http://groups.yahoo.com/group/NEDRA)
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
For EV drag racing discussion, please use NEDRA
(http://groups.yahoo.com/group/NEDRA)
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
For EV drag racing discussion, please use NEDRA
(http://groups.yahoo.com/group/NEDRA)
