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 knocking, oil consumption issues, and piston failures including breakages.
| Identifier | ExFiles\Box 82\1\ scan0098 | |
| Date | 9th April 1933 guessed | |
| - 5 - gradually became very sharp and distinct untill in our opinion, would not be passable after the engine had become hot. In the second and third gears it was most pronounced. A knock developed in the torque reaction dampers when the engine idled and slow running was uneven. The out of alignement of the dampers was the cause, which was cured. There has been no marked torque reaction period. The engine remained free from detonations by the use of Esso petrol which is a benzoline mixture only. Preignition was only noted once, through a weak mixture being obtained by the failure of the petrol supply. The breather to the crankcase was found to be inadequate, and was the cause of the engine burning unnecessary oil. The oil being drawn up the breather pipe. This was cured by an adaption being fitted to the crankcase oil filler which made it the breather, at the same time, retaining its capacity as a oil filler. An increase of 200 miles was obtained in oil consumption. A sketch has been previously sent to Derby of the scheme. The rocker cover joint has been very poor for retaining oil. The quantity of oil escaping down the cylinder block makes a very dirty engine after a long sustained run. PISTONS LOP. E.{Mr Elliott - Chief Engineer} 55804. E.{Mr Elliott - Chief Engineer} 56610. As reported there was an exhaust blow into the crank chamber when the car returned from Mr. Bentley's trip. When dismantled the failure was found to be the pistons. The retaining split pins had worked out and the chattering had caused excessive wear of the pistons, at the ends of the gudgeon pins. The cylinder bores were alos damaged. A new cylinder block and pistons E.{Mr Elliott - Chief Engineer} 57122 were fitted. Two of these pistons broke very quickly, the head parting from the skirt. It was found that the pistons were weak in tensile strength, which was the cause of the failure. A new set of pistons E.{Mr Elliott - Chief Engineer} 56610 were fitted made in the correct material. These pistons gave no trouble untill 4,877 miles had been run. It was then discovered upon draining the oil out of the crank chamber, that a portion of a piston skirt had broken off. There had been no indication whilst driving the car that anything had happened. Upon dismantling the engine it was found that N° 3 piston had a section of the split skirt broken. It had broken from the cross cut diagonally downwards. It did not in anyway affect the running of the engine and did not cause any damage. The other pistons were taken out, cleaned and examined, but no sign of cracks or fracture were apparant. The scraper ring on N° 4 piston was broken approximately one inch from one end. We have had two scraper rings break on this piston. /a A peculiar feature was noticed with regard to the gudgeon pins. With no exception the six pins had worked | ||