At 08:04 AM 1/23/99 -0800, Armand & Lorie Ritchie wrote:
>>
>>Well I must comment on this one Bob. All kidding aside have you or jay or
>>anyone else actually tried this theory of yours or is this strictly
>>hypothetical. That is that a smaller bore master cylinder gives you more
>>braking force. Because quite frankly I think your all full of bull. A
>>mechanic friend proved it to me by showing me on his car, that the bigger
>>the bore the more fluid you push through the lines which greats more
>>pressure at the wheel cylinders. Remember the wheel cylinders those are
>>the ones that actually do the work of stopping the car. Let the flames
>>begin I'm putting on my fire suit. regards Armand
>>
>
>ritchie@mcn.org
>Armand & Lorie Ritchie
>
Armand,
I can't speak for Jay, but I most certainly have, on many occasions, tried
this (not) my theory in practice. The most recent example is with regard to
the clutch master cylinder, which has a 5/8" bore for a stock Tiger and
3/4" for the Alpine. The difference in applied (foot) force between these
two units goes as the area of the bore or the square of the diameter, which
is a factor of 36/25 or 44% more pedal force needed to operate the 3/4"
unit. While needing this much more pedal force, the bigger unit has a like
reduction in the travel needed to accomplish the job, so the total work
done by your foot with each unit is the same. This is just the hydraulic
equivalent of the mechanical advantage tradeoff with a longer or shorter
lever arm. Oh yes, and the result of switching these units in my car was as
expected, much harder to operate the 3/4" unit, although honestly I did not
quantitatively verify the 44% harder factor. Nor did it even occur to me
that this effect needed verification.
While even I sometimes criticize those in academia who live in an "Ivory
Tower", you have to remember that virtually all the engineers who design
cars, planes, bridges, rockets, etc., etc., have learned the theory for
their craft in university. Computer modelling, based on known and usually
rather precise theory allows today's engineers to design complex systems
with a great deal of confidence as to their performance. This greatly
shortens the development time and costs and produces a result that both
works better and costs less to build. Now it's always amusing when some Art
Arfons type bends up something in his back yard and goes out and sets a
land speed record, but in the long run it's the guy with the good
theoretical foundation who's going to succeed.
Feeling the pressure in San Diego,
Bob
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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