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).
Letter to Col. Robinson discussing vehicle performance, modifications to brakes, axles, and clutches for heavy loads.
| Identifier | ExFiles\Box 182\M21\ img068 | |
| Date | 28th June 1921 guessed | |
| Col. Robinson. -2- DA{Bernard Day - Chassis Design}7/G28621 Contd. Mr. Royce is also of the opinion that if a great weight like 9688 lbs. has to be carried down 1 in 4, it would be desirable to increase the brakes somewhat, and this would be done in the new axle. Though we think that the increase of ratio will overcome the trouble with the cooling, we will experimentally find out what we can do on this point, and if the altered ratio is not sufficient we will do something else, but we may say that the standard cars are, if anything, over-cool except in extremely hot conditions. We will also be preparing for any emergency, by experimenting with ferodo lining on the clutch with a view to making it more capable of taking punishment, though we think this will not be necessary with the other modifications. If it is found that this type of clutch is not suitable for this sort of work we shall be pleased to design another clutch which will go into the same space if possible. We have gone into the question of the performance of the cars on Friday the 17th instant, and think that the following figures may be of interest to you. The M.E.P. at the road wheels of a car with low compression pistons is 73.5 at speeds up to 1100 or 1200 R.P.M. The total weight originally tried was 9688 lbs. To climb a gradient of 1 in 4 with this weight represents a M.E.P. of 109.5 lbs.sq. ins. shewing that this performance is impossible. With 38" wheels the maximum gradient that the car can pull this weight up is 1 in 6.25, or with 40" wheels 1 in 6.63 The maximum weight which the present armoured cars can take up a gradient of 1 in 4 with 38" wheels is 6480 lbs. or with 40" wheels 6150 lbs. (Contd.) | ||