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 piston seizure, proposing increased clearance and detailing an inspector's account of a specific failure.
| Identifier | ExFiles\Box 74\3\ scan0071 | |
| Date | 31th January 1929 guessed | |
| 2. There certainly has, during the test of this type of engine, been a greater tendency for the pistons to seize up than with the "Eagle" type of engine, and we are of the opinion that a .002" increased clearance could be allowed to advantage. At present the clearance is .008". It is proposed to increase this to .010". Trouble was experienced in this respect with the early 75 HP engines as made by Brazil Straker, which had .008" clearance, but which was increased to .010". According to reports, the following is a history of the engine's running, from our Inspector :- "It has made several short flights - in all about 1/4 hour. They then started up on Saturday and inform me it was a few revs down and making a clatter. The Pilot got off the ground, oil pressure O.K. and engine reasonably warm. When he had attained a few hundred feet, this clatter got very much worse and he noticed his oil pressure was down. Immediately he came down and they got me to go and see this trouble. When coming down the clatter got worse and worse." The cause of the oil failure was found to be due to the poor joint between the oil pump and the filter, which, as previously reported, is rather usual with this type of engine, even though when it leaves the Works it is quite satisfactory. It is also found that the piston was out of action, and an examination revealed the above fault. Half the piston was jammed at the top of the cylinder, and the remaining half was reciprocating with the connecting rod. Also, it was not considered wise to merely replace the piston and the cylinder, as there was a considerable amount of "powdering" from the piston which had spread generally over the internal parts of the engine, and it was considered advisable that the engine should be returned to the Works and completely dismantled and overhauled. | ||