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).
Technical memorandum discussing the design and stress testing of the Phantom III gearbox.
| Identifier | ExFiles\Box 94\2\ scan0229 | |
| Date | 10th May 1937 | |
| 328 Rm.{William Robotham - Chief Engineer} --- c. E.{Mr Elliott - Chief Engineer} Dd. E/HDY.{William Hardy}1/HP.10.5.37. Phantom III Gearbox. With reference to the design on which we are working for a box of Wraith size for use in the Phantom, we are fixing the gear widths to give a stress of 61,000 on the overdrive ratio at 3740 lbs/ins torque (B.M.E.P.105). Standard Bentley or 25/30 constant mesh 65,000 lbs/sq.in. The only gear tooth failure we have any record of, excepting early 20-HP. cars, is a 3 1/2 litre Bentley constant mesh pinion the stress in which is 56,000 lbs/sq.in. This was attributed to faulty carburisation. The stress in the teeth of the Standard Phantom box with overdrive gears which has just run on the dynamometer for 151 hrs. at 1500 r.p.m. full torque is 46,300 lbs/sq.in on the constant mesh gears and 41,000 lbs/sq. in. on the overdrive gears. It appears to us to be advisable to make further tests with a higher stress to determine, if possible, whether our figure of 61,000 lbs/sq.in is going to be satisfactory. We suggest that a standard box is fitted with Cadillac gears and run on the 3rd speed. The stress will be 74,500 and the end load 2,720 lbs against an end load of 2,345 lbs. on the box we are designing. The end load on the box on test is 1,210 lbs. The heating of the box with 45° Cadillac gears will be more in accordance with what will occur with our design. The tooth load on the proposed box will be 55% greater than on the box just tested, and the amount of sliding on the teeth will be greatly increased by the use of 7 D.P. teeth instead of 10 D.P. The oil drag in the proposed box will be less but the surface area is also less. Hdy{William Hardy} E/HDY.{William Hardy} | ||