> On Oct 9, 2015, at 9:43 AM, Anthony Jackson <xxxxxx@iii.com> wrote:
>
> From: Jeffrey Schwartz
>
>>> Back when I was into moto-cross the rule of thumb, for motorcycles anyway, was that one lb of unsprung weight = 3-5 lbs of sprung weight as far as handling was concerned...
>>>
>>
>> I wonder how that changes with "active suspension" technologies?
>
> Well, the active suspension will need to be bigger and more powerful if it's controlling bigger wheels, so there's a fair chance that it's even worse with active suspension. However, just cutting down the number and length of mechanical links can help, and there are control advantages to being able to apply force to each wheel separately, so one motor per wheel has likely benefits no matter what.

Also I wonder how much of that rule of thumb applies when the ‘unsprung weight’ is essentially the wheel itself, especially in the case of hub motors.

Heavier wheels will be better gyroscopes, and thus harder to change direction quickly, but this is the same problem that motorcycles face, and they adjust by leaning; also with four independently steering drive wheels you can do some really cool stuff, like steer each end of the car in a different direction to get turned.

I remember a long time ago (ca. 1969-72-ish, maybe as late as '75) reading a Popular Science article about a car with just that kind of setup.

--
Bruce Johnson
University of Arizona
College of Pharmacy
Information Technology Group

Institutions do not have opinions, merely customs