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).
Crankshaft stiffness, calculations, and comparisons with other engine designs.
| Identifier | ExFiles\Box 25\3\ Scan336 | |
| Date | 23th April 1928 guessed | |
| contd :- -2- The corrected stiffness of one crank is 2.11 X 10^6 lbs.ins/rad; your formula gives : 2.00 X 10^6 " " " , so that the ratio calculated/test stiffnesses = .950 or within 5% The large drop in stiffness when most of the bearings are removed is of interest. We have found it as large as this once before in the case of E.76545. Both shafts had been stiffened up elsewhere except in the crankpins, the latter shaft having been weakened still further there. It appears that this noticeable reliance on the support of the main bearings is characteristic of the shafts whose weakest link is the crankpin. The crankpins of E.54640 will shortly be increased in diameter, which should make the shaft more uniform both in stiffness and stress. We also attach a sketch of the crankshaft of the straight-8 Stutz car - an American car which we had the opportunity of investigating. (3) We give in tabular form our attempt at the calculation of our car engine periods using the equations of Chree, Millington, and Sankey. You asked us to do this as a comparison with the method we usually use of taking one-third of the total inertia as concentrated on the nose. We could not complete this table, as the chart that you gave in your paper "Dynamic Forces in Aero Engines" only goes as high as q = 1. We send it as far as we have got, so that you may complete it from your own information and curves. Should you be able to do this, we should be grateful if you could fill in the second copy and return it to us. If you have by now got curves which enable this method of calculation to be carried out for 6-cyl. engines for higher values of q than unity, we should be very interested to have a copy of this also. (4) We return herewith your copy of the Journal of the Royal Aero Society containing your paper on crankshafts, for the loan of which we are very grateful. We must again apologise for the delays in sending you this information, but it has required a certain amount of calculation and preparation, and we have been very busy over other jobs requiring immediate solutions. contd :- | ||