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).
Modifications and concerns regarding the 20HP chassis, including body weight, back axle ratio, and engine improvements.
| Identifier | WestWitteringFiles\P\2October1926-December1926\ Scan089 | |
| Date | 3rd December 1926 | |
| TO BJ. FROM R.{Sir Henry Royce} C. to HS.{Lord Ernest Hives - Chair} DA.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} IHS. SG.{Arthur F. Sidgreaves - MD} R2/M3.12.26. re. 20HP. BACK AXLE RATIO, WEIGHT OF BODIES ETC. X5350 X5830 X4538 X8350 You will remember that I have always disagreed with a large and heavy body on this chassis. At the moment I disagree with a wide or heavy body, high and top heavy, which naturally we all disagree with. Regarding accessories I do not think we can influence these more than by our recommendations, but our recommendations for a given chassis should be clearly printed and put into the hands of every purchaser of a chassis. As regards fenders (bumpers) we think there is little need of these providing the spare wheel is carried at the back for protecting the petrol tank. Anyway we think it is only necessary to use this ugly addition at the back of the car. I think we should strongly discourage fitting them at the front, because we are trying our utmost to avoid excessive weight on the front wheels of our car, both for steering and riding qualities. One very strong objection to a large body, in addition to spoiling the performance of the car, is that this chassis shall not compete with the 40/50., or spoil the RR. reputation. If it does we had better not sell it at all: it is just as unsuitable to fit on this chassis some of the large and heavy bodies I have seen (one in the Showrooms), as it would be to put a large body on a Morris-Cowley. Regarding altering the back axle ratio I am willing to do this experimentally, and have instructed a trial set of gears having a 10 toothed pinion, with 47, 48, or 49, wheel, preferably 47, as this will give a slightly stronger gear, and I hope a sufficiently high ratio. It should be remembered that this engine is only about 45% of the Phantom in capacity, and therefore the weight of the body ought to be limited to something like 60% of the weight of the body on the Phantom. An immediate change we propose to make for the next 10,000 miles car is the above back axle, and the stiffer crankshaft. I believe there is some modification needed to make this stiffer crankshaft entirely satisfactory, namely the adoption of the aero engine crank webs, which permit of longer intermediate bearings. On this engine there will be an improvement in the exhaust, giving slightly more power, and some modification to the induction system with the object of maintaining the MEP. at higher speeds, and hoping to get a better MEP. We shall not attempt to alter the length of the stroke as this will only be increasing the weight of the engine. It will be understood that this chassis is light compared with other 20HP. chassis used for similar purposes. The vertical louvres will be ready, and there may be some modification to the front axle control. R.{Sir Henry Royce} | ||