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 failure analysis, vibration reduction, and material considerations for components like crankshafts and rods.
| Identifier | ExFiles\Box 179b\1\ img311 | |
| Date | 4th February 1933 guessed | |
| (2) (6) Regarding the reason for the failure being worse at No. 1. end of the engine I think it would be safe to conclude from the evidence of the split pins that vibration at this end of the engine is greater than near No. 6. The reason for this increased vibration may be due to the torque of the crankshaft throwing the pins near the node more out of line, or it may be due to the influence of the teeth of the spur gear, or a combination of both. I do not know how we can reduce this except by a Bibby type coupling between the pinion and the crankshaft. I understood that the type we suggested from WW. behaved very well on test, but little advantage could be detected in its use, while it was naturally cumbersome and expensive for weight (which might be reduced.) It would however have a material influence in preventing the vibration of the gearing reaching the crankshaft and reducing the distortional vibration of the crankshaft by shifting the node nearer to the centre of the engine, in which case one would expect it to be less severe. (7) Some of these remarks are very difficult to comment upon or to prove whether they exist or not, but I give them for the consideration of RG.{Mr Rowledge} and HS.{Lord Ernest Hives - Chair}, the matter being of the utmost importance and urgency. I think however that good progress is being made in increased knowledge of what happens, even if it brings forth nothing more than negative evidence. (8) I understand that the articulated rod is difficult to get in because the liner has to be shortened, and this prevents the scraper ring being at the bottom of the piston. For future engines we should if necessary boldly raise the crown of the cylinder the required amount, and for existing low rating, low speed, engines we might try modifying the piston to get effective scraper ring higher up, allowing the required reduction in liner length, first proving if there is, or is not, any advantage in this type of rod, as I have been endeavouring for a long time to get admitted or contradicted. (9) You will remember that it is only a few weeks since the possibility of external lead bronze was found possible, without which we seem in a very hopeless position with the blade type rod. (10) I have long ago thought that hardened shafts were quite a necessity with this lead bronze, and our loading, and to my mind the production of non-hardenable crankshafts should be stopped at once. R.{Sir Henry Royce} | ||