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).
Technical letter from Wellworthy Piston Rings Ltd. detailing bearing specifications for interference fit, nip, and working clearances.
| Identifier | ExFiles\Box 115\5\ scan0019 | |
| Date | 22th April 1938 guessed | |
| 1. cannot be taken in establishing a sufficient oil supply; this particularly applies to bearings for use in high speed high performance engines, where explosion and inertia loads can be very high. INTERFERENCE FIT. We recommend that bearings are fitted with their outside diameter greater than the diameter of the housing into which it fits. The figure we usually work to is 0.0005/inch diameter. NIP OF BEARINGS IN HOUSING. By nip of bearing, we mean the amount by which the bearings halves stand proud of the joint face. This should be 0.001" on each side of the bearing relative to the joint face for each half of bearing. WORKING CLEARANCE. We recommend the following clearances for bearings - (a) CONNECTING ROD BEARINGS. For connecting rods we find the following clearances satisfactory :- Minimum - 0.001 / inch diameter. Maximum - 0.0013 /inch diameter. (b) MAIN BEARINGS. For main bearings where crankcase and crankshaft distortion must be taken into account, we find that the following clearances are necessary :- Minimum - 0.0012 /inch diameter. Maximum - 0.00155 /inch diameter. Preferred - 0.00135 /inch diameter. We look forward therefore to having blue prints of the applications which you have in mind, when we should be very pleased to put up the proposition to you and make bearings for you to try out. Yours faithfully, For WELLWORTHY PISTON RINGS LTD., Technical Manager. | ||