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 and considerations for 25HP and 45HP car components.
| Identifier | ExFiles\Box 65a\3\ scan0305 | |
| Date | 3rd September 1931 | |
| HS.{Lord Ernest Hives - Chair} FROM E.{Mr Elliott - Chief Engineer} C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} XHH40 R3/M3.9.31. Sent off 7.9.31. CAR WORK. X.3993. X.5770. X.7770. 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 dis., 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 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 with labels: E.S, 15º, 50J, 25º 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 | ||