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).
Issues with driving springs, damping, friction discs, and potential timing errors on a 20 HP model.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan095 | |
| Date | 19th July 1928 guessed | |
| contd :- -2- If we could get away from metal stops, the trouble could not exist, perhaps we should be better off if we made the spring come choc-a-bloc as a stop. We feel that rubber with its variable rating and damping might make a good driving spring. Chryslers use it for another purpose in their slipper wheel. (4) Owing to the damping we have to use for reason (3), the driving springs cannot be made stiff enough to avoid zero error. Thus when the drive is on the stops on the 20 HP, the damping is 17 lbs. ft, while the spring drive restoring couple is only 7½ lbs.ft. Therefore unless special precautions are observed when re-timing an error of ± 5° may be made. The continual variation of this amount on the road does not seem to affect the running of the car. As the starting handle torque is taken through the damper springs, if this means of turning the engine over when timing is utilised, the driving element will be brought up against the stops. (5) We are not yet sufficiently happy with our friction discs to be able to fit up a damper with a given spring deflection and get a specified load; We therefore find that the lack of adjustment on the damping springs makes setting the damper difficult. It will be observed that none of the points mentioned prevent the device from working experimentally, they are really features that are only likely to cause trouble on production. Since, however, our new stiffer crankshafts have pushed the master period well above the maximum useful engine contd :- | ||