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).
Example calculation for clutch pedal leverage and cylinder size for a 16 HP car.
| Identifier | ExFiles\Box 128\2\ scan0198 | |
| Date | 12th October 1933 guessed | |
| CC.1/4 -4- EXAMPLE OF CALCULATION FOR LEVERAGE AND CYLINDER SIZE. Assume a car about 16 h.p. size with normal clutch. We will first consider the loads on and movement of clutch pedal - these can be measured with pressometer gauge or by spring balance. [Diagram of clutch pedal and cross-shaft with the following labels and measurements: A, B, C, D, 1", 3/4", 1/2", 12", 1 1/4", 2 3/4", Clutch Cross-shaft] In above diagram - D is the position of the clutch pedal when the clutch is fully disengaged with pedal pressure (measured) say 35 lbs. C is cushion point position. B is clutch fully engaged. B to A represents free movement of clutch pedal, which is gradually taken up as the clutch wears. Now with the layout as above, the maximum torque on cross-shaft to fully disengage clutch is (35 x 12 x 2.75 lbs ins.) / 1.25 = 924 lbs ins. Assuming cylinder to work direct on to a lever on the cross-shaft, the required length of lever = Torque on cross-shaft / Pull of cylinder With Size B. cylinder 924 / 54 = 17.1" With size C. cylinder 924 / 84 = 11" It is not usual to use size C. cylinder on engines having a capacity of less than 2 1/2 litres, in order to keep the quantity of air dumped into engine on clutch release at a minimum. We should therefore select B. size cylinder. | ||