Analysis of rear axle stresses and gear ratios for fitting a P.2 engine into a J.3 chassis.
| Identifier | ExFiles\Box 123\3\ scan0005 | |
| Date | 2nd May 1933 | |
| BY. {R.W. Bailey - Chief Engineer} from DA. {Bernard Day - Chassis Design} C. Sg. {Arthur F. Sidgreaves - MD} Wor. {Arthur Wormald - General Works Manager} Hs. {Lord Ernest Hives - Chair} E. {Mr Elliott - Chief Engineer} -------------------- X4704 DA. {Bernard Day - Chassis Design} 1/G. 2.5.33. P.2. ENGINE IN J.3. CHASSIS - REAR AXLE. -------------------------------------- If the engine is the 8.1 litre Phantom and the rear axle the existing J.3 with a 4.1 axle ratio, the stresses are as follows, with those in the Bensport(Codename for 3 1/2-litre Bentley) which broke placed alongside for comparison - lbs. per sq. in. TABLE 1 | In the Hypoid Gears. | In the Differential Gear. | In the axle driving shafts. | | P.2.J.3. | Bensport(Codename for 3 1/2-litre Bentley). | P.2.J.3. | Bensport(Codename for 3 1/2-litre Bentley). | P.2.J.3. | Bensport(Codename for 3 1/2-litre Bentley). | | 174500 | 135500 | 187700 | 191500 | 69500 | 54600 | We think that the J.3. axle in conjunction with this engine is rather near the limit. If we use an 11/41 ratio on the J.3. axle (same as P.2) of which a drawing exists, the following are the stresses :- TABLE 2 | In the Hypoid Gears. | In the Differential Gear. | In the axle driving shafts. | | 158000 | 170000 | 63000 | These may still be thought to be high, and we suggest providing a gear ratio higher than standard P.2. (11/41). This seems to be justified by the following figures :- TABLE 3 | | Weight cwts. | Engine c.c. | Axle Ratio | Wheel Rad. | Max. Engine r.p.m. | Max. MEP. | Accl'n. figure of merit (Max. engine cc. x axle ratio x MEP. / Weight x wheelbase) | MPH. at max. engine speed. | |---|---|---|---|---|---|---|---|---| | Bensport(Codename for 3 1/2-litre Bentley) | 30 | 3669 | 4.1 | 14.5 | | 115 | 39.8 | | | P.2.Stan. | 48 | 7668 | 3.72 | 15.5 | 3500 | 110 | 42.2 | 86.8 | | P.2.J.3. 11/41 | 43 | 8100 | 3.72 | 15 | 3500 | 110 | 51.6 | 86.8 | | P.2.J.3. 12/41 | 43 | 8100 | 3.415 | 15 | 3500 | 110 | 47.1 | 91.5 | | P.2.J.3. 13/41 | 43 | 8100 | 3.155 | 15 | 3500 | 110 | 43.6 | 99.0 | With the two last ratios, the stresses are as follows :- TABLE 4 | | In the Hypoids. | In the Differential gear. | In the axle driving shafts. | |---|---|---|---| | 12/41 | 145,500 | 156,600 | 58,000 | | 13/41 | 134,500 | 144,600 | 53500 | | ||
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).