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 discussing piston ring clearances, excessive oiling, and the potential use of Simplex piston rings.
| Identifier | ExFiles\Box 148\3\ scan0150 | |
| Date | 24th August 1936 | |
| WELLWORTHY PISTON RINGS LIMITED CONTINUATION No. -1- W.A.Robotham. Esq. 24th August.1936. Handwritten note: Is this so. If so we should try more clearance & use Standardplex? on the Rolls Royce Piston. Of course, although we have always been great believers in keeping the clearance behind the ring down to reasonable proportions, many years ago probably you may remember that Mr. Hives was having excessive oiling on certain Aero engines, and we recommended he should reduce but not more than 5 minimum and 8 thou maximum clearance behind the ring. Having seen the pistons and seen the sizes after they were checked up on the Rolls Royce piston it was quite possible for the ring to be almost touching the bottom of the piston, and if it should so happen that any rings got through slightly over the radial depth, or you had for some reason exceptional expansion of the piston, such as say hard driving, either on test or in the early stages, this is going to start cylinder wear and will lead also to extra oil consumption if not cause seizure. I think possibly this was one of the most important points that occurred to me on looking through the job at our Works here. The other was, which no doubt Mr. Blackith discussed with you, the pistons were oversize as far as the bore was concerned, which would allow if pressed into the engine contraction on one side only, which would be likely to cause excessive pressure on the cylinder wall on the non-thrust side. One final word with regard to Simplex. I note from Mr. Blackith's report you did not fit any Simplex whilst they were there, but I would like to impress upon you Simplex is really going to save you money and a lot of trouble from a service point of view. Austin recommends it in his service manual which is privately issued to their Service Depots and not only he but quite a large number of manufacturers all use this ring in their Service Depots, and I would like to suggest that if you have a car which has been returned to you during the service period, either in London or at Derby, and if you do not want our mechanic to come up, fit them yourselves, but if you would care to send the pistons down here or let our people in London have the pistons, they would fit the rings and let you have same and the clamps ready for assembly. I am sure you would find this is a very real help in combatting excessive oil consumption and slight piston slap. With regard to the car on order I naturally should like our own pistons in if possible but I am not going to allow this for excuse to hold up delivery, but I do hope that the visit I had the pleasure of paying and that Mr. Blackith | ||