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 failures, cold starting issues, misfiring, and design for maintenance.
| Identifier | ExFiles\Box 125\1\ scan0203 | |
| Date | 5th March 1935 | |
| -2- ENGINE. The new connecting rod bushes and gudgeon pins failed again after a 1,000 miles running due to lack of oil. It was found that the release valve was too lightly loaded, which dropped the oil pressure too much at medium speeds, combined with the increased oil flow from the bearings due to wear. The oil feed to the gudgeons via the connecting rod was not of sufficient duration. We found it necessary to have a groove milled in the top half of the connecting rod bearing to give more duration of supply. After doing this and loading the release valve, no further trouble was experienced with lack of oil to the gudgeon pins and bushes. The engine retained its power and smoothness under normal temperatures, no difficulty was experienced in starting up. However, it failed completely to start after being left for two days during cold weather in the open, temperatures round about zero. The failure to start was entirely due to non-vapourisation of the petrol and not sufficient speed of the engine to create sufficient depression in the induction pipe to draw petrol to the cylinders. In this case the car had to be towed to obtain a start. Slow running was generally very good, with a total absence of any transmission noise. We had a period of misfiring which was due to the sticking of the eccentric bushes of the silent tappets holding the valves full open. There is no adequate filter fitted. The engine was free from oil leaks chiefly owing to the efficient breathing of the crankcase. The design of the engine is very clean and for Depot work and production cuts out a lot of unnecessary labour. To remove pistons and connecting rods, the operation consists of removing the lower half. The lower half joint does not disturb either the flywheel joint or timing case joint. After removing the lower half the connecting rods can be uncoupled and by turning the crankshaft the rod and piston can be withdrawn. The skirt of the cylinder is well tapered so that in refitting the piston rings are gradually closed in without much danger of breakage. To do this work it is only necessary to remove the ignition plugs on the top of the engine. | ||