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).
Suspension improvements, focusing on rebound movement, check straps, and shock damper performance.
| Identifier | ExFiles\Box 95\3\ scan0060 | |
| Date | 31th January 1935 | |
| -2- Hs{Lord Ernest Hives - Chair}/Les.3/KW.31.1.35. With the Dubonnet suspension car 19-G-IV, we have been able to increase the rebound wheel movement from 3.300" to 4.625". This has reduced the discomfort over the bump to a large extent. The front wheels now scarcely leave the road, whereas before they were off the road for several feet. In order to retain the same difference in comfort for SpectreCodename for Phantom III between normal road conditions and a bump, as on Ph.II, we shall require a considerably greater improvement. The reason why the Americans use such a small front rebound movement appears to be in order to overcome rolling on corners. We find that the good normal riding of SpectreCodename for Phantom III is ruined on corners, because one wheel is always riding on the bump buffers. A roll rod on the front would appear to be essential for SpectreCodename for Phantom III in order to prevent the necessity of more bump movement. The hump-backed bridge problem on SpectreCodename for Phantom III where the rear of the car goes up at the same time as the front goes down on to its bump buffers, can be attacked from both ends of the car - (1) To check the rebound stroke at the rear. (2) To check the bump stroke at the front. Re-Bound Check at Rear. Fitting a check strap at the rear to prevent more than 3" rebound spring movement is unsatisfactory. The sudden acceleration has already taken place, the passenger having left his seat, so that by checking the movement of the rear of the car the roof is brought closer and the seat taken further away from the poor human in space. It is impossible to check the rebound earlier than 3", as even this adversely affects the normal riding of the car. Delco Inertia-Controlled Shock Dampers at the Rear. These dampers, due to an upward acceleration of the body of the dampers attached to the frame, increase their rebound load from 70 lbs. to 350 lbs. for the whole of the rebound stroke. On a hump-backed bridge these show a distinct improvement provided the adjustment permits the inertia to operate early. However, with such an adjustment the normal riding of the car is impossible. We are fixing up electrical contacts so as to ascertain exactly when the high pressure rebound comes into operation. This will enable us to learn if there is sufficient margin for the inertia to operate on a | ||