Re: Senza Lavoro part 2, Long & wordy

[John Mallinckrodt <ajmallinckro@CSUPomona.Edu>]

On Fri, 14 Nov 1997, brian whatcott wrote:

> A person wanted to size the mass of an inertia wheel for an inertial engine
> dynamometer last week.
> He wanted to permit HP measurements to 100HP at up to 10,000 RPM allowing a
> 10% rise in rotation rate over 10 seconds.
>
> I assumed all flywheel mass concentrated in the rim.
> I equated the work input to the extra distance the rim moved at 10000rpm + 10%
> in 10 secs.
>  This did not compare with the difference of the beginning to ending
> kinetic energy of the rim.
>  I hastily computed 800 lbs.for the rim. I'm fairly confident this was wrong.
>
> If anyone is motivated to work this example ( assuming it is a suitable
> candidate,) I would be glad.

Because there are a few statements in the above that I can't make sense
of, I may well be working a different problem.  At any rate, I equate the
change in kinetic energy, delta (I omega^2/2)--to the input power times
the time interval and find that I = 153 lb-mass ft^2.  Since you did not
specify the radius of the wheel, I can go no further.  Assuming 800
(lb-mass) is the answer, I would get a radius of gyration of about five
and a quarter inches which would also be the radius of the wheel if all
the mass is concentrated in the rim.  (Was the diameter about a foot?)

Love those engineering units!

John
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