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 power, weight ratios, and engine capacities of the 20 HP chassis against other models and competitors.
| Identifier | Morton\M2.2\ img005 | |
| Date | 12th April 1929 | |
| Notes on 20 HP Chassis. has increased in power very considerably since the 20 HP was introduced in 1923, the power of the 20 has not increased in anything like the same proportion. This is shown fairly clearly in the following table: Type. Max: Power Complete Weight & 3 passengers Power Weight. 40/50 HP Silver Ghost. Pre FWB. 66.5 5840 1.14 Silver Ghost FWB. 66.5 6030 1.1 Phantom 85 6230 1.36 SS.{S. Smith} 105 5720 1.84 20 HP Complete Weight & 2 passengers Original Model 37.5 3810 .985 Present production 40 3976 1.01 From this it will be observed that, whereas the 40/50 of 1923 had a power weight ratio of 1.14 and the 20 a power weight ratio of .985, the 40/50 has increased to 1.36 and, when the "SS{S. Smith}" comes in, to 1.84, but the 20 has only increased to 1.01. Mr. Royce says that the original intention was that the 20 should be about half the rating in tax and capacity of the 40/50 which means half the power, whereas with the Phantom at 85 maximum power, the "SS{S. Smith}" at 105 and the 20 at 40, it will be seen that, when the "SS{S. Smith}" is introduced, the 20 HP will not be up to the original intentions. Item 7. Mr. Royce mentions that other 20 HP cars have better performance because of light factory made bodies and speedometers which do not read correctly at higher speeds, but it should, we think, be pointed out that the cubic capacity of the RR is less than that of many of our competitors. For instance: 20 HP RR. Cylinder capacity...3132 c.c. Sunbeam 25 HP do ...3619 c.c. Chrysler 66 HP do ...3580 c.c. (struck through) 20.Austin...3400. 25 Buick...3920 20/24 Minerva...3370 21 Lanchester...3327 25 Daimler 3568 (Handwritten) These particular cars are selected as being ones that we are frequently compared with for performance and body capacity. | ||