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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).
Comparison of braking units for the J.III & Peregrine models against the 40/50 & 20/25, with proposed modifications.

Identifier  ExFiles\Box 13\1\  01-page30
Date  11th November 1932
  
V 7360.

For Files. 11.11.32.
K5360
x4047

J.III BRAKES & PEREGRINE.

Comparing the four Cars on the road we get:-

Braking 40/50. 20/25. J.III Peregrine.
Units.

Direct. 377 377 240 220

Rear & 499 524 525 388
Front
Servo.

Peregrine suffers from too little direct
braking. If we make the pedal reach the boards
sooner by increasing the direct braking, we can
also increase the mechanical advantage between the
servo and the shoe, as when the pedal hits the
boards we are forced to take up a notch, therefore
preventing the servo hitting the stop.

On Peregrine, therefore the direct braking is
increased from 220 units to 377 units by increasing
the length of lever by 377/220 or 70% and the rear and
leverage from the servo to the shoe brought up to
the original front leverage from the servo to the
shoe by increasing the length of lever G.100533 from
2.750 to 4.2 on 53%. With the short levers from
the front equalisers forwards, therefore, the
distribution of units becomes Direct 377. Servo,
front & rear.

On J.III the direct is brought up from 240
to 400 units by increasing lever G.55388 from 1.6
to 2.65" or 66%. The servo to front and rear is
increased slightly(but only slightly, as with 524
units the 25Hp. servo comes on the stop rather
early) by 6% making the servo lever to the rear
G.55391, 2.38 instead of 2.25 and the servo to
the front lever G.55419 2.00" instead of 1.875.
  
  


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