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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparative analysis of two servo designs ('40/50' and 'S S') using calculations for braking forces and wheel skid characteristics.

Identifier  ExFiles\Box 16\3\  Scan029
Date  12th December 1928 guessed
  
contd :-
-2-
with a 'flick' application
possible to lock the front wheels, of the pedal, whereas with gradual application the rear wheels would always skid first.

It would therefore appear that for consistency and efficiency, the larger the radius at which these driving pins are fitted the better.

Comparing the two servos - we have -

40/50.
Friction disc radius 3.00
Cam radius .544
Cam angle 45°
Assumed μ .1

For any pull 'Y' from the pedal, pull X =
Y X 2.625/.544 x 3/1 x 5.8/2.05 x 2/7.85 = 1.06

'S S'
Friction disc radius 2.6"
Cam radius .580.
Cam angle 45°
Assumed μ .1

For any pull 'Y' from the pedal, pull X =
Y X 2/.580 x 2.6/1 x 5.5/2.05 x 2/8.5 = .565

It would therefore appear that disregarding the reduction in driving pin radius, the contd :-
  
  


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