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).
Dynamometer test report on the Vulture gearbox, detailing failures and proposed modifications.
| Identifier | ExFiles\Box 123\3\ scan0169 | |
| Date | 12th April 1934 | |
| Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls}15/KW.12.4.34. VULTURE GEARBOX. We have run a dynamometer test on the 2nd speed Synchromesh gearbox fitted to the Vulture. For these tests a rear axle torque arm was fitted so that 1st gear full torque should not damage any other parts of the car. At the beginning of the test the box was fitted with a 50:50 mixture of engine oil and Whitmore's compound. Half an hour at 2000 r.p.m. full throttle was completed on each forward gear. Oil temperatures of 117ºC. on 1st gear, 115ºC. on 2nd gear and 125ºC. on 3rd gear were reached during the tests. The lubricant was then changed for engine oil only. After 10 minutes on 1st gear the teeth had picked up and clicking noises developed due to failure of a pinion tooth which had started a fracture at the root. The 1st speed gears were the narrow original type, i.e., not strengthened by thickening the pinion and decreasing the wheel. Fifteen minutes on 2nd gear with the torque arm removed was successfully completed without heating the needle bearing universal joints. Failure of the dynamometer prevented further tests. It was noticed that oil leaked from the servo shaft and from the front of the gearbox. On the present type of unit construction box there is a pressure in the clutch pit. We suggest the lack of this feature is the cause of this oil leak at the front, and that better breathing arrangements are therefore required. Further oil leaks have been noticed during road running. We have also fitted 55º cams to all speeds. Since this alteration changes of gear have been free from crashing. Deliberate crashing of the teeth did not adversely affect the gear change. More effort is of course required on the lever to overcome the oil friction, although in top and 3rd speeds it is less than on a standard 40/50. We shall try 8º cones on the 2nd speed, screw threaded to prevent sticking, and revert to a 45º cam. For the dynamometer test we are fitting wider strengthened 1st speed gears in SZNCR material. Hs{Lord Ernest Hives - Chair}/H.{Arthur M. Hanbury - Head Complaints} Grylls. | ||