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).
Polishing methods for worm gears and nuts to prevent sticking, and the development of a steering test rig.
| Identifier | ExFiles\Box 154\3\ scan0014 | |
| Date | 11th March 1927 | |
| -2- nut when engaged on any of the three threads. But the surface finish was grey rather than the fine "black" polish of the English model. We were finally able to produce this polish by running the worm fast (about 400 r.p.m.) in the lathe and polishing with a hard-wood half-nut and a 180 alundum powder followed by fine sand. The polishing was done dry. We found on the guillotine (with castor oil) that the sticking was completely cured by this polishing, even when used with nuts which had not been thoroughly burnished and which consequently showed a poundage as high as 11 or 12 lbs. (1200 lb. load). From which we gather that:- (1) The burnishing of the white-metal is responsible at least 50% for the poundage, but has no effect whatever on the sticking. (2) The polish of the worm faces has less effect on the poundage but is of the utmost importance for sticking. So that, with a burnished nut and a non-polished worm we can get 9 lbs. on the guillotine but stick badly. With a non-burnished nut and a polished worm we can get 12 lbs. on the guillotine without a sign of sticking. We have made a "cranking rig" for taking the complete steering, having a side steering tube coupled to a shaft with a hand-crank. On this same rig we can arrange to hang 440 lbs. on the end of the 11" pendulum lever and so test the steering for possibility of "parking". We can also arrange to heat up the box to any desired temperature by a gas flame. The history of the use of this rig is most interesting. When originally used for hand-cranking with a light smear of castor-oil as lubricant, the steerings were irreversible until started by the steering wheel, and gradually became reversible after half an hour or so. Improved worms made it just possible to reverse them when new, and a great improvement was noticeable in half an hour. | ||