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).
Providing recommendations for bearing interference fit, working clearances, and crankshaft hardness.
| Identifier | ExFiles\Box 115\5\ scan0002 | |
| Date | 2nd February 1938 | |
| Messrs. Wellworthy Ltd. -2- 2nd. February 1938. 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. Crankshafts. We are recommending at the moment that manufacturers should only use these bearings in conjunction with hardened crankshafts. Our experience has been mainly confined to hardened shafts and for that reason we are not at the moment supplying bearings unless they are to be used with a hardened shaft. We have tried connecting rod bearings on a shaft of 340 Brinell with success but have no experience with main bearings. We recommend a hardness figure of 600 as a minimum for crankshafts. | ||