Give us a little more time, Garfield, and we'll be able to deduce your very existence from first principles!
Actually, I don't understand any of this very well. That's why I was bugging Flyboy to explain how come such different "weight equivalencies" kept popping up.
I see what Flyboy means about those suspicious formulas in cells D24 and D28. I know even less about spreadsheets than I know about most things, but lemme see if I can figure out what those variables coorespond to. (I won't even attempt to work out what the formula actually
does.)
Ah ha! If you double click on the the C24 cell, the "real" formula is revealed as:
0.5 * t2M *(w2Radius^2 + t2Radius^2)
This is supposed to equal the rotational inertia of the tire alone. Excel's nice color-coding system leads me to believe that:
t2M = the second tire's mass, in 'slugs'.
w2Radius = the second wheel's radius, in feet.
t2Radius = the second tire's radius, in feet.
So yeah, since the wheel's radius is the same as the tire's "inner" radius, this does seem wacky.
I'll try changing the formula to what Flyboy suggested and see what happens... Good, that seemed to reduce the calculated "torque difference" between the heavy wheels and the light wheels by about 30%. That drops the weight ratio that we've been discussing into the 2.6-3.2 range, depending on how the weight distibution is modeled. Still above what Flyboy is betting on, but quite a bit closer.
Oh, but I've been modeling lighter tires than Garfield's. Lemme change that. Nah, I also was assuming a lighter car. When I plug in the same weights as Flyboy used, I get a ratio up around 4:1 again. Sigh.
I still think it has something to do with the rate of acceleration. (Not speed, acceleration.) Are we
sure that rotational inertia scales the same way that linear inertia does? (I'm just making up terms now!)
-Dave
PS. My car's delivery was delayed. Again. But I'm assured that I'll get it tomorrow. (I've heard that before!)
