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 bumper drums, threaded shackles, rear axles, and suspension systems.
| Identifier | ExFiles\Box 153\1\ scan0061 | |
| Date | 23th September 1937 | |
| -3- is even greater with an oscilloscope with a powerful flashing light combined, for some jobs, with a dull continuous light. Under these conditions the vibrating part is shown in slow motion by the oscilloscope while the path it follows is shown faintly as a loop by the dull light. Our bumper drums at present have two cams per drum giving a spacing of 6 ft. We are making additional cams so that we can try the 3ft. spacing recommended by Olley. The disadvantage of the wider spacing is that subsidiary vibrations of higher frequency can be set up between the cams so producing a compound vibration which is more difficult to analyse. Threaded shackles. Olley knew of no instance where threaded shackles had seized up and did not think special precautions were taken to keep out dirt. He suggested that the clearance should be proportional to the dia., i.e. our large dia. pin requires more clearance, and possibly the pin should not be hardened but merely heat treated to 400 brinell as U.S. practice. Buicks are giving up the open shackle as they have had several cases of failure. This is attributed to sideways loading. The threaded links of the Oldsmobile open shackle are twisted out of parallel to prevent rattles which occurred when they were parallel. When threaded bushes are fitted to rolled spring eyes, the bushes are turned with 0.007 interference and then knurled. Rear Axle. Vauxhalls are adopting straddle mounting for the back axle pinion and Olley enquired whether we ground our crown wheels. Suspension The arrangement of concentric torsion bar and tube employed on the 25.HP. Vauxhall is being repeated on the new 10.HP., and they have machines running endurance tests on these with a stroke of 5 1/2". They have found that finishing the torsion bars and tube by shotblasting is superior to a 'mirror' ground finish - Olley says it is less delicate - and with this type of finish they are going up to a maximum stress of 135,000 lbs/in.2 in the torsion bar without trouble. They are endeavouring to keep the stress in the tube down to 75,000 lbs/in.2. The shotblasting finish is also applied to the toggling spring in the Vauxhall 25.HP. (supplied by B.S.C.) and Olley says that all american manufacturers except Buicks shotblast their springs, and Buicks do not make good springs. If our main suspension springs are not already finished in this way it might be interesting to have some that are and see if there is any gain. | ||