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 Alta Car & Engineering Co. Ltd. discussing connecting rod clearances, seizure issues, and design improvements.
| Identifier | ExFiles\Box 27\2\ Scan212 | |
| Date | 15th May 1934 | |
| X/775 c. to Mr. Wilson. c. to BY.{R.W. Bailey - Chief Engineer} Exptl. Dept. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}14/KW. 15th May, 1934. The Alta Car & Engineering Co.Ltd., Fuller's Way, Kingston Bye-Pass, Surbiton. Dear Sirs, In reply to your letter of May 14th. We think that the clearance of your big ends is rather unnecessarily large. On a 2¼" connecting rod pin we have only been running a clearance of .00075". Your pin being smaller, the clearance should be proportionately less. We do not think this has any bearing on the seizure; it might lessen the tendency of the rod to hammer out under extreme conditions. With regard to the seizure, our experience has been that unless these rods are run in rather carefully they are liable to seize. We have only had one such case. We do not attribute this to grit because if the feed holes are drilled below the centre line of the pin, the crankshaft acts as a centrifugal cleaner and no dirt gets to the bearings. We should not expect the connecting rod to fail when it seized, and think your design is open to criticism. In these light alloy rods the shoulders are almost invariably the weakest point, and we send a design showing how this point can be improved. You will note on the design that a steel cap is shown, but this is not necessary. We have never used any special oil for lubrication, nor have we any oil grooves in the bearings. | ||