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).
Investigation into contact lines on helical gears using celluloid models and stress analysis.
| Identifier | ExFiles\Box 174\2\ img070 | |
| Date | 27th March 1937 guessed | |
| -6- (7) Helical Gears. By celluloid models they have been investigating contact lines etc. on helical gears. They have found that if you set up a thin aluminium strip on each end of a cylinder so that the cylinder has the base circle diameter, and the aluminium strips (which have the involute form of the required tooth) being mounted in the correct relative position and the teeth roots being connected by a shallow groove machined in the cylinder at the helix angle, then a celluloid tooth can be inserted to match that groove as follows :- [DIAGRAM TEXT] DEVELOPED HEIGHT OF TOOTH THESE ARE SECTIONS OF TRUE CONCENTRIC CIRCLES LINES DRAWN TANGENTIALLY TO THE BASE CIRCLE DEVELOPED LENGTH OF TOOTH The celluloid strip above will fit the groove and the straight lines tangential to the base circle will stay straight and will be lines of contact with the mating gear. Gear failures which occurred at Hudson have been eliminated by chamfering the tooth edge along one of these lines so that all the existing load did not occur on the tooth tip. Further tests with celluloid gears using polarised light for stress analysis show 75% variations in tooth pressures obtained locally when cutting by minor changes in cutter forms. This has not yet proceeded far, however. | ||