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).
Test report on a Phantom III gearbox (HS8), focusing on the performance and bedding-in of fine thread synchromesh cones.
| Identifier | ExFiles\Box 94\1\ scan0326 | |
| Date | 7th February 1936 | |
| X328 To E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to Hdy.{William Hardy} c. to By.{R.W. Bailey - Chief Engineer} c. to Hs.{Lord Ernest Hives - Chair} Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux}2/KW.7.2.36. Phantom III Gearbox HS{Lord Ernest Hives - Chair}8. The test on this box was chiefly to see whether the synchromesh cones with a fine thread would bed in and become efficient, without the necessity of lapping in by hand with plain cones. The first test on the road, the synchromesh of the 2nd and third gears operated satisfactorily with the exception of a slight lumpiness. The top or direct synchromesh was lumpy and crashed when warmed up. With use, the 2nd and third synchromesh improved but the top became worse. We dismantled the box. Examination of the top cones proved that they were not bedding correctly. The fine thread of the brass cone showed bedding at the extreme bottom and none at the top. A test with mandrels proved that the two angles were correct, therefore the discrepancy of out of alignment lies in the box. To allow for this the steel cone was released at the bottom of the angle. Upon again testing the box, the top synchromesh had improved but was still not as good as the other two. We therefore lapped the cone in, whilst running the car, and after a period of lapping, this synchromesh improved and the change of gear was good. Examination of the cone afterwards found it still hard on at the bottom of the cone. The fine thread had been practically flattened and worn down to the solid face, whilst the fine thread still showed at the top. The third synchromesh cone was bedding evenly. The result of this test confirms that providing the machining of the male and female cones are correct, and the alignment of the gear boring is correct, these cones will bed themselves in and will be efficient. This box has got 9° angle cones for the third and top, and 8° cones for the second gear. We have run the box, making approx. 1000 changes with no sign of sticking or jamming of the cones. We are now of the opinion that the box should be fitted in one of the Phantoms. We are handing over the box to H.Smith, to quieten the gears and investigate a heaviness in the selector mechanism. Hs{Lord Ernest Hives - Chair}/C W.Hancock | ||