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).
Design analysis for an ideal car sill, comparing uniform and concentrated load calculations.
| Identifier | ExFiles\Box 14\8\ Scan291 | |
| Date | 23th June 1930 guessed | |
| - 2 - This curve gives us the depth of an ideal sill of uniform width and variable depth that will satisfy our fundamental requirement of constant curvature under load. This is shown by curve II and the dotted line gives us a straight line envelope of this curve and suggests the shape the sill should be made. The above is based on an arbitrary uniform load of 20 lbs. per inch. To determine whether this is justified we have made an attempt on SK-404 to divide this up into concentrated loads as below - Starting from the dash - at 0" we have the cowl and its framing - 150 lbs. 22" " " windshield and its framing - 300 lbs. 42" " " 2 passengers - 300 lbs. 52" " " front pillar and doors - - - 400 lbs. 78" " " 2 passengers - 300 lbs. 84" " " Rear pillar and doors - - - 400 lbs. 108" " " 2 passengers - 300 lbs. 120" " " Rear end - - - - - - - - 250 lbs. Total - 2400 lbs. Again curves I and II represent Bending Moment and its cube root. The dotted line is the suggested sill and is taken off SK-403. The interesting point is the extreme closeness with which the sill depth derived with concentrated loads agrees with that obtained with uniform loads, the only appreciable discrepancy being that the max. at the rear is a little higher and the rear point of inflexion a little further forward with the concentrated loads than with distributed loads. From this we believe that for all practical purposes we are perfectly justified in assuming a uniform load on the sill of 20 lbs. per inch run. Another interesting point is that we are able to reduce the depths of sill at the rear point of inflexion - and this point, with the suspension as arranged coincided with the front edge of the wheel housing, where we do not find it possible to obtain the maximum depth of sill. We have shown on DL-89 a preliminary attempt to put the above into practice. This is laid out on the basis of an 8" deep sill - the top surface of which runs flush with the floorboards right back to the wheel housing where the depth can be reduced to about 5" to clear the rear spring. The rear body support is located at a point 9" ahead of the rear axle and is taken on the point where a deep crossmember - represent-ing the rear seat heelboard meets the frame - using the standard parts of the English front Subframe Suspension. This point 9" forward of the axle is chosen for these reasons - - continued - | ||