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).
Required improvements for 25HP & 45HP models, including balance weights, propeller shafts, cooling, performance, and carburetters.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan398 | |
| Date | 7th September 1931 | |
| HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} ORIGINAL CAR WORK. R3/M3.9.31. Sent off 7.9.31. x3993. x5770 x7770 A few things we must have quickly: (1) 25HP. & 45HP. BALANCE WEIGHTS. Balanced crankshafts partly at least preferably hardened. Present stock forgings waiting for WW. (2) 25HP. & 45HP. PROPELLER SHAFTS. HS.{Lord Ernest Hives - Chair} says my J.{Mr Johnson W.M.} 1. still suffers from the propeller shaft being too small in dia. therefore we want these of sufficiently large dia. I understand P. 2. is quite satisfactory, and the larger one already on 'China'. (3) 25HP. & 45HP. WATER COOLING. The dented tubes and non-spilling valve are very good moves. Means of allowing air to escape from under the bonnet must be carried out effectively, even to using the most effective louvres, but I hope our standard will be '31' type shutters even if 4 or 5 per side are needed. This is important and urgent. I want what is our standard on the 25HP. continental tourer that I am to use, but sincerely hope for shutters because of noise and cold weather. I am definitely against the smaller dia. tubes because it means greater heat under the bonnet, and small benefit for the great cost and weight. MOTTO: Let air freely in and out. (4) 25HP. & 45HP. PERFORMANCE. I have given our views in another memo. I am just a little afraid of loss of silence etc from the higher valve lift, but this high lift seems very effective for high rev: performance, and we have suggested slight modifications to cams and rockers as a compromise. We seem to have got to the limit of valve timing, including overlap. Perhaps the inlet could close a little later and exhaust open a little later, but the cam length of 57 and 61 div: seems about right. E.{Mr Elliott - Chief Engineer} thinks we should go to greater acceleration than we have on 25HP cams. We have on some cam forms this last 2 yrs. - .0045 [Diagram showing valve timing with labels: I, E.15., 50I, E.50. and a note '15º of overlap.'] (5) CARBURETTERS. The S. U. horizontal is nearly good, but lacks a few virtues that we think are necessary, and it would not be diplomatic to use this unless we are obliged. It will be realised that the last MPH. is less important than many of the other features, especially missing fire with very light charges. We are hoping to get good results from fixed throats but it seems somewhat doubtful yet, so we make the best of our old one, which is only beaten on maximum peak HP., and wins on many points. | ||