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 torque, deflection, and design issues in a testing apparatus arm and bearing assembly.
| Identifier | ExFiles\Box 141\2\ scan0278 | |
| Date | 29th March 1939 | |
| -2- Rm{William Robotham - Chief Engineer}/JBD.{John B. Dixon - Fuel Systems}6/JH.29.3.39. A simple method to which the drive would be to arrange a contact on the disc working the existing pan which if the drive was accurate would give equal distance between marks. It also appeared that alterations in the position of the arm carrying the test pieces had a definite effect and it was possible to feel a distinct change in the torque developed by the test pieces if the arm was depressed or raised and there was one position which it became unstable and juddered. The change in torque was not that caused by the measuring balance this being equal for equal deflections of the arm. The only effect that could cause this seems to us must be a self servoing action of the test pieces caused by deflection of the arm under different loadings. When we consider the design of the arm this seems feasible, see attached sketch. Both bearings are behind the test piece surface which is producing the torque that is assuming the centre bearing on the shaft driving the disc has some slack in it and does not take load, or that when loaded the small shaft deflects. The torque generated is resisted at only one end of the arm which will produce a downward free on the bearings acting through a plane coinciding with the surface of the test specimen. As both bearings are behind this plane a couple is generated tending to twist the arm in a plane at right angles to the direction of rotation. Whereever there is loading there is deflection, and we suggest we try to eliminate the load by taking the torque equally on each end of the arm and in a plane in line with the friction surface. At the same time it would be advisable to apply a constant down load on the shaft to prevent chatter, though this may not be essential as these bearings are very tight. A direct check on the axis of the arm and that of the disc could be made by fixing a clock on the arm and rotating it on the stationary disc. | ||