[ausev] hub motor noodling

[jefoy at mindspring.com]

In consideration of unsprung mass, Formula cars (Formula Ford, F1, Formula Atlantic, etc) all use inboard mounted brakes on the rear axles. THe rotors and calipers are mounted next to a stationary differential so at the wheel there is only the mass of wheel and hub plus half the mass of the axle.

You could use this concept with hub motors by eliminating the differential and mounting the motors in it's place. This would obviously be easier with models that started as four-wheel drive, possibly a conventional FWD motor/transaxle combination with hub motors in the rear for accelerration assist..

-----Original Message-----
>From: Chris Robison <eeyore at phototropia.org>
>Sent: Jun 13, 2006 12:31 AM
>To: ausev at austinev.org
>Subject: Re: [ausev] hub motor noodling
>
>On Mon, June 12, 2006 7:42 am, MLAB said:
>> I just got my renewed EAA membership card, so I think I will write this
>> post that has been on my mind for a while.
>>
>> I deal with hub motors a lot since my EV work involves bicycles and
>> tricycles (for myself or for clients).  I know that hub motors are used
>> on electric cars as well, such as that ugly-as-sin but ridiculously fast
>> Japanese 8-wheeler that graced the cover of a recent EAA newsletter.
>
>Arguably the most important function of a suspension is not to provide
>comfort for the occupants but to A) force a wheel that's hit a bump back
>down onto the road as quickly as possible and B) make it stay there (not
>keep bouncing). Add mass to the wheel (eg. by adding a heavy motor to it)
>and you've made that job a lot harder. A wheel hanging in the air after a
>bump provides no traction or grip for cornering. This problem increases
>rapidly with speed, and wouldn't be much of an issue with bikes or small
>scooters.
>
>I'm guessing the eight wheels on the Kaz and Eliica concepts most likely
>reduce the problem caused by any one wheel being momentarily airborne
>after a bump.  Or perhaps I'm wrong and that's why you only see these cars
>zooming around smooth oval tracks.  :o)
>
>
>
>> So every time I see a Geo Metro (or the like) sputter past, I imagine
>> stripping out the motor and drivetrain and attaching hub motors on all
>> four wheels.  The front two motors would be identical, with low and
>> medium-low speed windings, and the rear motors would be similar with
>> medium fast and fast windings in each.  All four motors could engage at
>> low speed for extra torque when needed, but normally only the front
>> wheels would drive from a start.  This would give the car 4 speeds, and
>> save room on the chassis for batteries.  Some sort of differential would
>> connect between the steering sensor and the throttle system.
>
>Maybe there's something I'm not thinking about here, but I'd say any time
>you have a motor with more than one winding where the windings are used
>individually and/or optionally, you've got certain operating modes where
>some of that copper amounts to nothing more than dead mass. Probably
>better to have all the windings in use at all times, but wired in a way
>that gives you different gearing (similar to what I'll be doing with my
>truck). Take advantage of the fact that you have four motors; make all of
>them simple and identical. Wire them in parallel for high speed and in
>series for high torque. Four motors would give you 3 basic speeds (all
>series, two series sets of two in parallel, and four parallel). Simpler to
>manufacture when all the motors are the same, simpler to repair, far
>broader performance envelope as long as the motors can handle the current
>and voltage extremes.
>
>  --chris
>
>
>
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