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).
Subframe defects, engine compression ratios, and their effect on noisy and booming car bodies.
| Identifier | ExFiles\Box 67\1\ scan0178 | |
| Date | 10th May 1926 guessed | |
| (6) to carry the load. (2) that the subframe crossmembers were weak, and would not prevent the side member heeling over and allowing the side pillars to fall out. Instead of overcoming these defects the entire design was changed (no doubt due to Mr. Charles having left). We cannot go into details of all the changes and various subframes which they have issued. This we will deal with in a separate report. Suffice it to say that each change made has produced worse results. We have taken Mr. Charles original effort and attempted to remove the defects. In spite of the original opposition to the idea originally by the coachbuilders, and in spite of the subsequent changes of design and the fact that in order to get the subframe to be used universally the latter was supplied free of charge, yet have they persisted in its use. This leads us to believe that they realise that they get a real advantage thereby worth striving for. It is rather significant that they are using the following compression ratios on their various models, and yet they have a closed car market:- 6/20HP. C.35. 16/55HP. 20/70 25/85. 35/120. 4.8 to 1. 5 to 1. 6.2 to 1. 5.6 to 1. 5.28 to 1. 5.07 to 1. The New PhantomCodename for PHANTOM I compression ratio is 4 to 1. EFFECT ON NOISY AND BOOMING BODIES. The Daimler experience with high compression engines has led us to investigate the effect of the subframe on noisy and booming bodies. At present we are relatively immune from serious complaints in this connection with production bodies, due possibly to the Phantom engine running at slightly LOWER speeds, and lighter reciprocating parts. We do hope to increase the compression ratio and so put up the HP of both the Phantom and the Goshawk engines, detonations being overcome by the improved design of combustion head. In view of this there is every likeyhood of our having to deal with slightly increased torque vibrations. The advantage of the subframe in preventing these vibrations from being felt in the body was demonstrated to Sales officials over a year ago on GF68 ( see report C9/CI.II.24.). By bolting the body rigidly to the chassis it was possible to convert what was described as an ideal trials car into a very unsatisfactory and noisy example. Although we have built two enclosed limousines with semi-domed roofs ( a body which has caused us considerable trouble in the past) on 8KX and 9PK. without taking any precautions to prevent booming yet this trouble was not encountered in either case. An exact replica of the enclosed limousine on 8KX, but | ||