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).
Results of extensive tests on Phantom III gearbox synchromesh cones.
| Identifier | ExFiles\Box 94\1\ scan0349 | |
| Date | 5th March 1936 | |
| X328 To E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Hdy.{William Hardy} Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux}7/KW.5.3.36. Phantom III Gearboxes. We have carried out extensive tests with the synchromesh cones to determine the causes of failure, angles of cones to give good smooth synchromeshing, etc. The results obtained have definitely established the fact that whatever angle of cone is used, it will not function correctly without the bedding being approximately 100%. With the correct bedding, lighter plunger springs could be effectively used. This gives more positive action of the sliding sleeve and the full action of the cam. We have found from our experiments with various cone angles that the lightest synchromesh action is obtained by using 8½° for the 3rd and top and 9° for the second speeds. HS{Lord Ernest Hives - Chair}8 box with 9° cones for the 3rd and top and 8° for the second is not quite so light in action. We obtained exceedingly good results with 7° cones, but these very quickly became scored, losing their efficiency. In the HS{Lord Ernest Hives - Chair}3 box, the synchromesh for the 3rd and top has the non-rattle plungers fitted. The value of these plungers we have not been able to demonstrate, owing to the fact that 30-EX, the car used, is not in a state to obtain this value. This should be obtained, as so far no Phantom gearbox has had these plungers fitted, and we understand there has been no complaint of rattle. The fine thread turned on the bronze cones has been very effective. A poor synchromesh box can be made 100% with this method of bedding surface. We have made some 500 to 1000 changes with very little flattening out of the thread or loss of efficiency. We should, however, before going into production with the fine thread, run a box a considerable mileage. We have reported on the misalignment that occurs with the top cone, which has been made correct by making the small diameter of the cone .005" less. | ||