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).
Theoretical and practical considerations of using a wooden deep sill subframe versus a metal one for coachwork.
Identifier | ExFiles\Box 19\4\ Scan065 | |
Date | 25th June 1930 | |
X7772 To: Da{Bernard Day - Chassis Design}/EV.{Ivan Evernden - coachwork} c. Sg.{Arthur F. Sidgreaves - MD} c. By.{R.W. Bailey - Chief Engineer} From: Oy. c. Hs.{Lord Ernest Hives - Chair} c. Btn. Oy1/DM.{D. Munro}25.6.30. Subframe. In connection with the project for making coachwork on a standardised wooden "deep sill" rather than a metal subframe, Mr. Burton has done some very interesting work which is of course purely theoretical at this stage, but which suggests that a wooden equivalent of the subframe might not be deficient in the essential qualities of stiffness in bending and torsion. The calculations are for solid ash sills. In practice it is realised that a "sandwich" construction with sheet-steel centre is better, and this is contemplated and under construction experimentally. (1) The first point is that a solid section of wood is probably stiffer torsionally than a corresponding steel channel .100 thick. (In spite of a transverse modulus for steel over 200 times as great as for ash). (2) A solid rectangular section of wood, say 1¾" wide by 7" deep at the deepest section, would also be considerably stiffer than the subframe in bending. (In spite of a modulus of elasticity for steel over eleven times as great). (3) Btn. notes: "From the above considerations we may expect that the(wooden) sills in themselves may be considerably stiffer than either the subframe side members alone, or than the latter when a flat wooden sill is built into them". "Where we shall most certainly find we are deficient is in the attachment of the sills to each other, i.e. the crossmembers. Admittedly these will have to be stiffened up to produce comparable results. (This refers to metal "fold and weld" brackets instead of wood-joints.Oy.) "The tests now being carried out by Rm.{William Robotham - Chief Engineer} should be very interesting" (This refers to tests on sub-frame mount proposed some time ago.Oy.) "and the results of these, coupled with the trouble we had recently with thumping engines in which it was indicated very clearly that coachwork had a great deal to do with final performance of the vehicle, make it very clear that the two are very closely connected and must be considered together". cont'd.{John DeLooze - Company Secretary} | ||