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).
Performance comparison report against a Crossley car, discussing gear ratios, sand tests, and radiator boiling issues.
| Identifier | ExFiles\Box 182\M21\ img076 | |
| Date | 27th June 1921 | |
| To R.{Sir Henry Royce} from DA.{Bernard Day - Chassis Design} -2- DA{Bernard Day - Chassis Design}5/G27/6/21 Contd. shaft and also into what can be done in the back axle bevels. No other car did this required performance, as it is of course impossible, with a given H.P. and gear ratio, but they quoted against us the Crossley car specially made for work of this kind, which has an engine of 4.5 x 5.5 - four cylinders, and a total ratio on the low speed between engine and road wheel of 20.47. The diameter of the wheels was not known, but believed to be 38". This car carried 8064 lbs. only. They claim that this car did all that they require, but we pointed out that the displacement per mile per-ton was considerably more than our car, and this was agreed to. So it appears to resolve itself into a question of altering the ratio of the first speed to suit armoured cars. In addition to the test of climbing, they have a test of a car working its way across loose sand of the character that one meets on the estuary here above high tide, that is, quite loose and about 6 to 10 inches deep. Our car on this sand would not describe a figure of 8, but stopped at each bend on the top and bottom of the eight every time it was tried. It is probably impossible to calculate what ratio is required to overcome this condition, but they informed us that the Crossley car previously referred to did its figure of eight quite steadily without difficulty, so that would give us an indication that the modification in the gear ratio would probably overcome this difficulty. The other complaints that they have are that the car boils. This was especially observable on the sand test, though they also said there were signs on the hill climbing test. They took off a blanking plate which was on, and that improved things, but it appeared to us that the great trouble was that they had no bonnets, and as the boiling occurred on a following wind the trouble was due to them getting no draught through the radiator. (Contd.) | ||