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 testing of engine performance, axle bearings, and gearbox components.
| Identifier | ExFiles\Box 92\5\ scan0036 | |
| Date | 31th October 1935 | |
| -2- The SpectreCodename for Phantom III figures are calculated from 110 M.E.P. against 120 for the Vulture, and the .37 ratio 1st gear. The dynamometer test we carried out was therefore at 20% overload. Even with a 17% higher 1st gear than the .37 ratio, the SpectreCodename for Phantom III would be no worse than a Bentley as regards starting on a hill. The important issue from this is that a 3 speed box more or less necessitated for use with relay operation would be adequate for any climbing conditions. The duration of the test was 2 hours full throttle on 3rd gear, 2 hours on 2nd gear, 20 minutes on 1st gear and 30 minutes on 2nd gear. A longer test on 1st gear was prevented by the dynamometer being unsuitable for such high loads, giving trouble with wheel spin and seizing of the hand brake. As the road wheel thrust on 2nd gear was 2180 lbs., this was equivalent to 1st gear on a Ph.II or Bentley car. Our intention was to run 2 hours full torque on each gear as a Bentley axle had run this amount without failure. The temperature in the axle and gearbox was kept down to 125°C. by stopping the test every 15 minutes for about a quarter of an hour. Examination of the axle shows that the thrust half of the pinion bearing has failed and that the journal tracks are very "Brinelled". We have written the manufacturers to know if they can increase the capacity of this bearing. The other bearings are in good condition and the axle box is correct for alignment and free from cracks. The gear surfaces are also in good condition and were lubricated with Castrol Hi-Press. A certain amount of sludge was found in the pinion bearing, due presumably to the high temperatures reached during the test. Gearbox. The gearbox used for this test was the J-III box but fitted with 10 D.P. 25° obliquity unground gears. It will be remembered that the previous gears in this box, 12 D.P. 14½° obliquity, failed, the 3rd speed after half an hour on dynamometer and 2,000 miles, and the constant mesh gears after 2 hours on dynamometer. | ||