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).
Report discussing crankcase rigidity, flywheel bearings, and engine mounting designs.
| Identifier | ExFiles\Box 126\4\ scan0122 | |
| Date | 2nd May 1936 | |
| -2- various stiffened crankcases in aluminium and cast-iron, and we should immediately alter the pattern to improve the rigidity at the point in question. Taub says that they have got little or nothing out of stiffening the crankcase on the bearing centre line, but we can check this statement by static test. Taub says that to get smoothness it is necessary to have a crankcase which when loaded at the centre bearing and held on trunnions at either end bearing, will give a deflection of not more than .014" for a 4000 lbs. load. Whilst we think that we ought to reproduce this figure for the purposes of experiment, it is possible that we shall not have to go to such extremes because (a) we have a 7-bearing crankshaft, and (b) we use aluminium pistons. On the other hand, on the Bentley at any rate we are likely to be running at high compression ratios, with a greater rate of pressure rise. We are also likely to be running at higher engine speeds. Chevrolet also emphasized the necessity of having a rigid flywheel bearing, solidly attached to the main structure of the crankcase. We think that our weakness at this point is clearly demonstrated by our great susceptibility to flywheel inertia. The crankcases that are going through with the double bolt rear bearing should cover this point. (4) Grylls. Engine Mounting. Whyman. Taub quarrelled with our engine mounting on the SpectreCodename for Phantom III and 20/25 HP. because he said that the two front supports were too far apart. In his experience it is vital that the engine should be very free rotationally, and to get the necessary rotational freedom with the front supports so far apart and carrying the weight of the engine means that the engine has to move an unnecessary amount vertically. Taub is in favour of having a single support at the front, the only reason they have two on the Chevrolet is because of some patent situation. Chevrolet say that they find the best way of evolving an engine mounting is to put a piece of rubber in the position decided upon which has much greater freedom in one direction than the other, and then rotate it until they find which position gives the best results; i.e., let the engine move in the direction in which it wants to go. | ||