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 to a supplier providing feedback and criticism on experimental hand pumps, specifically regarding machining accuracy and piston clearance.
| Identifier | ExFiles\Box 139\1\ scan0181 | |
| Date | 24th June 1936 | |
| X1166 Exptl. Dept. 24th June, 1936. Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}10/KW. Messrs. D.{John DeLooze - Company Secretary} Sessions & Co. Ltd., 906, Harrow Road, Willesden, LONDON, N.W.10. Dear Sirs, We have now tested the four experimental hand pumps which you sent to us. We are returning these pumps to you so that they can be modified to the 3/4" bore port type, which we have decided on for production. As they are, they are of no further use to us, and after modification can be supplied with your production deliveries. We have one or two criticisms of the accuracy of the machining of these pumps: that these criticisms are justified is borne out by the fact that two pumps on production have recently seized. The two 3/4" bore pumps you sent have .0001" and .0002" piston clearance respectively. The 9/16" bore low pressure pump has .002" clearance one end and .0013" the other end. This is entirely due to bad finish of the piston, the bore of the casting being the same diameter throughout. The 3/4" pump which only had .0001" clearance was very tight to operate; we do not think any production pumps should have such a small clearance. The early type pump fitted to our 36-EX car has .0004" clearance and has given no trouble, and has a maximum pressure obtainable of 3000 lbs/sq.in. We think therefore that if the pumps you supply in future have a clearance varying from .0003" to .0004", no trouble will be experienced, but we recommend that more trouble is taken with the finish of the piston, as our inspectors criticised this point on every one of the pumps you have sent us. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||