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).
Modifications to the slipper drive on the 20 HP chassis to address load issues.
| Identifier | ExFiles\Box 74\2\ scan0376 | |
| Date | 14th December 1925 | |
| HWH BY6/H.{Arthur M. Hanbury - Head Complaints} 14.12.25. c. MX.{John H Maddocks - Chief Proving Officer} c. Hs.{Lord Ernest Hives - Chair} c. BY/so. SLIPPER DRIVE. As all the 20 HP. chassis suffer from apparent increase of load on the slipper wheel after the engine has been running, the increase in question being such as to put the slipper wheel unit right outside the limit at which it was agreed to pass, after going carefully into the matter with MX.{John H Maddocks - Chief Proving Officer} I find that the only way out of the difficulty will be:- a/- To obtain a supply of new springs approximately 50% of the existing ones. b/- to fit springs to only half the number of the holes. Since we have no special springs at the moment, a/- is out of the question. It therefore means that in order to prevent us building up slipper drives and taking them down again, to put matters right either here or at the coachbuilders, we must adopt the proposal under heading b/-. Will the works therefore kindly arrange to build up all future wheels with only half the number of springs, but instead of using oil freely in the building up, the slipper surfaces, both on the wheels and the fabric, should only be very lightly greased. Under these conditions, MX.{John H Maddocks - Chief Proving Officer} has found that he can obtain a load on the end of the 17.5" lever of 8 lbs. The works should work to a similar figure, which will be obtained so long as the slippers are only lightly greased, as pointed out above. The difference between the slipper wheel as built up with the full number of springs and the condition it arrives at after it has been running for some time is, that in the first instance there is an oil film which is maintained until such times as the engine gets thoroughly hot. Under hot conditions, the oil film breaks down and only a very light film of oil is lft. This results in the coefficient of friction going up to practically double what it was when the slipper drive was built up and oil freely applied during the operation. Contd. | ||