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).
Letter from Cadillac Motor Car Company discussing an analysis of Delco shock absorbers.
| Identifier | ExFiles\Box 170\2\ img020 | |
| Date | 16th April 1931 | |
| CADILLAC MOTOR CAR COMPANY DETROIT, MICHIGAN CADILLAC and LASALLE MOTOR CARS April 16, 1931. Mr. E.{Mr Elliott - Chief Engineer} W. Hives, Experimental Engineer, Rolls Royce, Limited, Derby, England. My dear Hives: Thank you very much for your extremely interesting analysis of Delco shocks. The diagrams have been rather a bombshell to Delco and us and we have not yet digested them, but are attempting to do so with an open mind. I have several comments:- (1) Pressure Curve. The typical diagram taken by Delco shows a flat-topped curve. It is taken by a rig as shown in attached sketch and is supposed to represent actual loads felt by the car. (You saw this rig at Dayton.) The diagrams differ entirely from those which you get, which all show, on the rebound (or high pressure) side, a marked tendency for the pressure to go on rising beyond mid-stroke. We should like to know therefore what is the time-displacement characteristic of the horizontal lines on your diagrams. In other words, where does the mid point of the stroke come on your diagrams? The Delco diagrams all start at the left and show a slight tendency to build up towards the right but not nearly as marked as yours. The time-displacement of the horizontal on these is almost exactly simple harmonic because of the very long connecting rod (about 3 feet long). (Note that, as shown in the sketch, the curve of piston velocity against displacement on the card should be an ellipse under these conditions, so that if oil pressure were exactly proportioned to piston velocity the diagram would be elliptical.) It is evident to my mind that the Delco diagrams are seriously at fault, and show undoubted evidence of sticking by dry friction in some part of the mechanism. | ||