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).
Analysis of vehicle frame stiffness, modifications, and torsional figures for different models.
| Identifier | ExFiles\Box 152\2\ scan0209 | |
| Date | 1st May 1940 guessed | |
| -2- 1. Frames. The rationalised frame is satisfactory except that the front end was found to be too weak for a standard soft top body. However, on all except 8-cylinder cars, it has now been shortened, and it is to be hoped that it will now prove satisfactory. 8 cylinder cars, if to be fitted with soft tops, must be watched, and may need the reinforcement which was built into the scuttle on 10.B.V. It was recently decided to try and put the exhaust system under the frame instead of through it, and for this purpose two upsweeps were required in the cruciform. This naturally reduced the torsional stiffness but, by adding 2 lbs. of boxing the stiffness was restored to its original figure. The rear upsweep has not yet been put in, and its position will need very careful consideration. From the point of view of stiffness it should be as near the side members as possible, while the exhaust people want it as near the centre as possible. The near side half of the cruciform will have to be made in two portions as it will be impossible to press it in one piece. The Studebaker frame gave the following torsional figures: Front to rear....700 lbs. ft/degree. Dash to rear....900 " " " Weight 144 lbs. Dash to Front...3,150 " " " Oy. has told us that a satisfactory car must have an overall stiffness between wheel planes of at least 3,500 lbs. ft/degree. B.V. is around 3,000 and Silver Phantom 2,600. We consider these satisfactory; the frame itself contributes 1,350 - 1,400 to this figure. A complete list of torsional stiffness figures will be found in the Frame Data file. It has been shown that lattice bracing of the channel section side members and cruciform gives a large increase in torsional stiffness for a small increase in weight (See figures for 30-G-VII and scrap B.V. frame in table). Apparently, however, there is a serious snag in welding them on as the welding is very expensive. --- | ||