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).
Comparison of standard Phantom type slipper drives and low inertia spring drives, focusing on overhang, vibration, and engine feet placement.
| Identifier | ExFiles\Box 14\2\ Scan060 | |
| Date | 1st November 1922 | |
| -9- inertia in the nose of the shaft, but only a small percentage reduction of the total inertia of the crankshaft system. We think the most important difference between the std. Phantom type slipper drive and the low inertia type lies in the reduction of overhang. On the former the whole rotating mass is supported on a nose 4" long. The nose in turn is supported from No.1 crank and our tests have now proved conclusively that this does anything but rotate smoothly, particularly with a piston and rod fitted. It is known that unless the std. type slipper wheels have a limited movement, they will shake apart at high engine speeds and hit the surrounding engine parts. The majority of the mass of metal in the low inertia type of spring drive is running on bearings on the nose of the shaft, and therefore is to some extent isolated, in addition to being supported much closer to the crank. (2) Engine Feet. Our tests have shown that large vibrations in the centre of the crankcase do not appear to reach the driver, yet apparently he is very sensitive to alterations to flywheels and spring drives which are in the neighbourhood of the engine feet. It appears then that if we had a pair of feet in the middle of the crankcase the car would be appallingly rough, and that the location of the engine feet on the S.S. already helps a great deal to subdue the | ||