Larry,
Since I just returned from vacation, your letter may be old by now. I would
like to give you some unsolicited information.
Larry Wright wrote:
> a) I don't know of a way to calculate PMoI
You can drive your car on a platform, suspended by cables, and turn it. After
subtracting out the platform actions alone you can determine the inertia and,
with load cells on each corner of the cable (or a platform scale taking front
and rear wheel weights individually) you can determine weight distribution and
c.g. This gives you the data to calculate moments of inertia.
> b) I don't see a _reasonable_ way to modify it (I'm not filling the bumpers
> w/lead, for instance)
That is correct, and probably negates any reason for doing a), unless your
curious, or have calculations that need the data.
> c) I am not certain we would _want_ to. Trade off nimble handling for
> stability enough and 'voila', we're driving Buicks.Or something else. The
> fastest I've ever driven, back in 1975, was in a 1958 Chrysler 300D. I
> think it was 5200 on the tach, worked out to +/- 150mph. Car was more
> stable than the Garage Queen at half that speed. But I sure wouldn't want
> to drive that beast on a twisty road!!!
As I recall, we used to put bags of concrete mix in the trunk to keep the rear
wheels from spinning, and improve handling, at the cost of acceleration at the
higher speeds. Band-aid engineering. Secondly, don't confuse "stability"
(resists changes in attitude or direction) with "handling" (accepts changes in
direction easily, precisely and without loss of control. The extreme case is a
car is so stable you can neither turn it, stop it, or accerate it. The
opposite case is the agile car that you must steer constantly to keep in a
straight line. Driven both. No fun.
> >I don't think an engineer would argue....
Of course we would. It is in the nature of engineers and scientists to argue
continually. This is not a fault, it is a part of the scientific method of
doubt until proof. It is what allows new discoveries. So expect it, and also
realize that, regardless of credentials, experts can be wrong. Remember all
those who did (and do) disagree with Einstein. Every month somebody uncovers
another proof of his theories.
> >If you want something easy to drive, don't buy a
> >Porshe (excluding the 944 of course) or a Tiger. But driven properly, they
> >can use their good maneuverability to advantage.
This is Bob's comment, and he is wrong. Both my Porsches handled very well, as
well as being easy to drive. Especially compared to a Tiger.
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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