There is more to it then this... remind me wed and I will explain my theory
on Trans ratios.... and rear gears... Land speed racing is absolutely about
gears and rear ratio's as well as Peak Rpm and cross sections of the torque
curve...
Gots to go racing with my Wide ratio short course trans.... NOT a
Bonneville trans...
Keith Turk
Austin Healey 100 / Bugeye / Box Sprite / Bonneville Land Speed Racer
Camaro ( D Gas Altered )
----------
> From: Daniel1312@aol.com
> To: ulix@u.washington.edu; spridgets@autox.team.net
> Subject: Or maybe not, was Re: I'm full of $#1^... :-)
> Date: Thursday, April 29, 1999 12:09 PM
>
> In a message dated 29/4/1999 5:38:00PM, ulix@u.washington.edu writes:
>
> << Simply not true! The rpm spacing between gears is determined only by
the
> transmission ratios. I had recently used the analogy of a 10-speed
> bicycle, but here the ratio change (front sprockets) is on the INPUT
side
> of the transmission (rear sprockets) and does in fact change the "close
> rationess" of the rear gears. >>
>
> Ulix, you were right the first time so I guess you are not full of the
> proverbial after all. The (admittedly incomplete) calculations prove
your
> original point - a taller diff has the effect of widening ratios, a
shorter
> diff brings them closer.
>
>
> 3.9 diff x wheel rpm = 3.9 x 911 = 3555.45
>
> 3.7 diff x wheel rpm = 3.7 x 911 = 3370.70
>
>
> 3.9 diff 3555.45 divided into 60,000 = 16.875mph per 1000rpm direct gear
(4th)
>
> 3.7 diff 3370.70 divided into 60,000 = 17.800mph per 1000rpm direct gear
(4th)
>
>
> 3.9 diff direct = 16.875 divided by 3rd gear (1.357) = 12.3455 mph
>
> 3.7 diff direct = 17.800 divide by 3rd gear (1.357) = 13.1171mph
>
>
> rpm increase 4th to 3rd on 3.9 diff at 3000rpm = 1,101rpm
>
> rpm increase 4th to 3rd on 3.7 diff at 3000rpm = 1,071rpm
>
> RPM increase is greater on 3.7 (taller diff) and this is why all you guys
> with 4.22 diffs don't worry about the wide ratios on the Jap boxes. Fit
a
> 3.9 diff and you might think twice about the Ford box (er hum which I
happen
> to have in my Sprite, er hum with close ratios anyway).
>
> Daniel1312
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