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).
Tests for an 'Acme Thread' lubrication scheme for a gearbox shaft.
| Identifier | ExFiles\Box 86\4\ scan0088 | |
| Date | 31th May 1934 | |
| Hs{Lord Ernest Hives - Chair}/WB.{Mr Brazier/Mr Bell}10/KW.31.5.34. "Acme Thread" Lubrication Scheme. The main object of these tests was to find whether or not oil could be pumped into the centre of a gearbox shaft by means of an integral screw thread. An arrangement as shown in the accompanying sketch was fitted up, a Bentley Steering Worm - F.58296 - being used as the pumping element. The tests were commenced with a sleeve giving .010" diametral clearance, covering 2" of the worm, and using Motorine 'C' at a temperature of 30°C. The effect of reducing the effective length of the thread was also tried, this being accomplished by lowering the whole shaft an inch. The tests were repeated with the diametral clearance reduced to .002" and finally - still with the .002" diametral clearance sleeve - the temperature was increased to 60°C. Readings up to 2000 r.p.m. were taken in 500 r.p.m. stages, the results being set out in the attached graphs as follows :- GRAPH I. Relation between effective length, delivery, and pressure - .010" sleeve, 30°C. GRAPH II. Relation between temperature, delivery, and pressure - .002" sleeve, 2" effective thread. GRAPH III. Same as II with 1" effective thread. An analysis of the results shows that reducing the length of "effective" thread reduced the free delivery, but not proportionally, the percentage delivery reduction being less than the percentage thread reduction, also the maximum pressure reduction was generally slightly less than the percentage thread reduction. It should however be observed that the actual length of the thread was not altered, but only the length covered by the sleeve. | ||