gearing

[JHertzman@domain.elided]

In AD7-751 C M Smith wrote "Properly designed cars will pull their maximum 
rpm in top gear, which should also equate to the maximum attainable speed for 
that particular vehicle, that's the way to set up a gearbox. Then the gear 
ratios should be spread so as to achieve progressive and efficient 
acceleration over the entire useable torque curve for the engine. The S does 
neither, sacrificing elegance for stop light GP's, which North American's 
equate to performance."

In 752 Richard Bies rebutted: "While I am going to agree with most of the 
comments of this post, I do disagree with this core statement.  <For street 
use>, I would suggest that the gearing should put the engine at a relativly 
low, quiet, rpm in the anticipated cruising range."

In days of yore Road & Track's road tests (and many others) included 
calculated data- MPH/1000 rpm, engine revs/mile, piston travel ft./mile, 
RPM@2500 ft/min, and equivalent MPH. The "equivalent MPH" at a piston speed 
of 2500 ft/min was commonly taken as a reasonable cruising speed for 
reasonable engine longevity.

The December 1959 R & T had three-plus road tests in a row: the Rover 
3-Liter, Volkswagen, and Fiat-Abarth twin cam, plus a "Classic" road test 
(interpolated from various earlier road tests) of the Ferrari 166 Mille 
Miglia Spyder (their spelling). The miles per hour at 2500 feet per minute 
piston speed were 76 for the Fiat-Abarth, 77 for the Rover 3 liter, 125 for 
the Ferrari, and 122 for the VW. Standing quarter mile times were 16.3 
seconds for the Ferrari, 18 for the Abarth, 21.6 for the Rover, and 22.8 for 
the VW. Top speeds were 125 for the Ferrari, 102 for the Abarth, 100 (est) 
for the Rover, and 71.5 for the VW.

Lots of other neat numbers to bandy around, but the 122 mph for the VW  was 
the one that got a lot of attention. The Ferrari was the one car of the four 
which had a five speed box with fifth an overdrive and fourth good for the 
car's maximum speed. The VW's third was almost strong enough to reach the 
car's timed top speed.

I would go with Bies' formulation. Top gear on a road car (whether one has a 
four, five, six or seven speed box) should be geared for fuss-free and 
mechanically painless cruising; the next gear down should be geared for the 
maximum speed desired, and the gears below that should follow Smith's 
formulation, "spread so as to achieve progressive and efficient acceleration 
over the entire useable torque curve for the engine".

Of course I am an un-Texan, both physically and psychologically; I really 
don't care whether my wife's 164 or my Milano will do 150, 200, or 300 mph. I 
rarely hit an indicated 100, and don't try to do wheelies at stop lights. 

Cordially,

John H.

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