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).
Engine overheating, focusing on fan belt tension and the effects of gear selection.
| Identifier | ExFiles\Box 24\5\ Scan062 | |
| Date | 14th May 1925 | |
| R.R. 493A (50m) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF HsEml/LG14.5.25. RE: OVERHEATING. With reference to H1/TB/11.5.25. We should like to point out that we do not consider, from the information contained in the third paragraph, that the method of driving was such as to promote the optimum cooling conditions. As we have previously demonstrated (See Hs{Lord Ernest Hives - Chair}10/LG 18.9.24.) climbing a hill on an indirect gear with a reduced throttle opening will give a slight cooling advantage provided that :- (1) The fan belt is absolutely dead-tight. (2) The engine is not run at a speed in excess of 1700 r.p.m. (Above this speed the fan belt is certain to slip). We assume that on 3rd. speed a large portion of of the hill would be climbed at from 35-40 m.p.h., this is equivalent to an engine speed of from 1810 to 2070 r.p.m. which would be above the critical speed mentioned. Though we do not suggest that on this occasion the fan belt was not taut, we feel the necessity for emphase ising the very considerable tension necessary in this drive if the fan is to be driven at high speeds without slip. This is the reason why we have always tried to avoid the recommendation of the use of indirect gears as a palliative to over-heating; if a customers fan belt is not tight he will be much worse off by changing down. If a customer uses a lower gear for faster work and better speed performance contd :- | ||