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).
Article on unit frame and body construction, comparing monocoque designs to separate body and chassis frames.
Identifier | ExFiles\Box 113\5\ scan0144 | |
Date | 30th August 1940 | |
1010 To Rm{William Robotham - Chief Engineer}/EAG. from Rm{William Robotham - Chief Engineer}/RG.{Mr Rowledge} Rm{William Robotham - Chief Engineer}/RG.{Mr Rowledge}2/ET.30.8.40. Re ARTICLE IN S.A.E. JOURNAL "UNIT FRAME & BODY" by L.W.SHERWIN. ------------------------- It would appear that the writer of the above article has been rather vague in his statements, giving very little actual data, but tending to favour the older form of construction, i.e. separate body and chassis frame. The chief known advantage, at the moment, of monocoque construction is the saving of approximately 100 lbs. or so in weight. One of our leading mass production car manufacturers had, from 1935 onwards, what was probably the lightest form of chassis frame ever constructed on his "8" and "10" horse power cars. This frame was constructed of .070 material and had out-turned flanges enabling the body sill to form the fourth wall of the box section. The body was bolted rigidly to the chassis member, thus giving an early form of unity construction and the riding qualities were considered quite good for a light car with normal suspension. The revised version of this car is, I believe, now completely monocoque, with a considerable saving in weight. Mr. Sherwin's suggestion that the cost of monocoque construction might be prohibitive with changing body styles is, I think, unfounded, especially if total production can be assessed at something like 25,000 cars. I think that it is a generally accepted fact that, if the seat spacing and the floor layout are ideal for one body style, they should be satisfactory for others. Even a Drop Head Coupé of the close coupled type can be readily adapted to this construction with additional brackets to replace such torsional stiffness lost by the complete steel roof. Experience has shown this practice to be necessary on the normally constructed car with separate body and frame. Agreed such changes as wheelbase and track would prove expensive, but minor revisions such as springing etc., should not be more costly than similar revisions to the normally constructed automobile. Theoretically, and I must say that I have no actual figures to quote, the production of a monocoque car should be less expensive than that of the normal type, providing there are not too many elaborate controls and gadgets. All live parts, i.e. engine, gearbox, controls, etc., should be restricted to as simple a form of sub-assembly as possible, so that they can be applied to the monocoque unit without necessitating the removal and replacement of loose panels and covers. Obviously then, the fewer applied covers, panels, etc., the fewer bolted joints and possible squeaks, apart from the labour costs to assemble. | ||