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).
Stress calculations for the propeller shaft under various load and braking conditions.
| Identifier | ExFiles\Box 77\1\ scan0103 | |
| Date | 11th July 1911 | |
| R.R. 235A (100M) (W 314. 8.3.11) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 1525 X484 TBB14/L11711. Mr. Johnson. July 11th 1911. Re Strength of Propellor Shaft. It is suggested in the attached report that the stress in the propellor shaft due to stopping the revolving parts is much greater than the maximum drag of the road on the tyres. In making this suggestion Mr. Bailey has assumed the maximum load on the tyres to be 28 cwt., i.e. the maximum dead load on the rear axle; I do not think this is a correct assumption because when the springs are deflected to the full amount, the maximum load on the tyres is far higher than the dead load and by actual experiment was found to be 39½ cwt. with a normal load of 26½ cwt., that is 50% greater. Assuming the worst conditions as follows:- Dead load 28 cwt. on rear axle. Highest gear 2.5 to 1. Maximum coefficient of friction between tyres and road .5. Then maximum load on tyres at full bump is 42 cwt. - drag of tyres on road 2350 [strikethrough] 2680 lbs. and torque on propellor shaft from this drag 15000 in.lbs. I have assumed above that a car fitted with the highest gear bevels may possibly be loaded up to 28 cwts. on the rear axle, this is not probable but I think may happen and should be allowed for. Added to the above torque of 15,000 in. lbs. is that due to stopping the revolving masses which may rise to a considerable amount if the wheels are stopped in a fraction of a second when the car is running at high speed. The torque from this cause alone would be as follows, - Car running at 40 m.p.h., wheels stopped in one second torque is 4900 in. lbs,- in ½ second the torque is 9800 in. lbs,- in ¼ second the torque is 19,600 in. lbs. | ||