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).
Letter to Dennis Bros. regarding crankshaft loading and bearing issues on a 'C' type engine.
| Identifier | ExFiles\Box 116\1\ scan0068 | |
| Date | 10th September 1938 | |
| Experimental Dept. Rm{William Robotham - Chief Engineer}/CTS.{C. Trot Salt - Carburation}1/MH.{M. Huckerby} 10th. September 1938. Messrs.Dennis Bros., Guildford, SURREY. Dear Sirs, Further to our letter of Sept.6th. and in answer to yours of Sept.8th, we note your remarks concerning the use of balance weights on the crankshaft of your 'C' type engine. Our Design Department have gone into the question of loading on the centre main bearing with the following result. Assuming a cylinder pressure of 600 lbs/sq.in. there is an angular deflection in the plane of the shaft (due to the explosive load), causing a deflection at each end of the centre journal of .003" (relative to the centre). An initial clearance of .006" will therefore be fully taken up by this deflection. We have gone through the previous correspondence from you, and we believe we are right in saying that failures have occurred at 3000 r.p.m. running at full load. We would like you to confirm the latter statement however, because this would match up with the effect of explosion loads. Also we would suggest comparing the relative strength of the crank webs with the crankshaft of an engine in which you are having no trouble with the centre main bearing. Finally, the obvious question arises, as to the possibility of using five main bearings in your 'C' type engine, because although balancing the crankshaft may be desirable, this will not get over the effect of the explosion loads. Yours faithfully, for ROLLS-ROYCE LTD. | ||