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).
Specifications for a new main armature spring for an SS starter motor.
| Identifier | ExFiles\Box 64\4\ scan0269 | |
| Date | 13th May 1929 | |
| Y7655 To EY/RD. from EFC. EFC/T13.5.29. MAIN ARMATURE SPRING FOR SS.{S. Smith} STARTER MOTOR. We are of the opinion from the results of trial on the latest longer travel armature motor on chassis 19-EX, that if we have not already done so, we should instruct experimentally the long intermediate rate spring Y, particulars of which are as follows :- Diameter of wire used. .056" Diameter of coil. .320" Number of turns. 63 Free length. 5.540 Rate. 7.14 lbw. per inch. Load in initial set up position. 6.00 lbw. Load in fully compressed position. 11.563 lbw. Estimated maximum stress. 68,800 lbw. per sq.inch. The reason for this is that the motor armature does not so readily come out of gear, causes rather more gear scream in doing so, and makes whirring noise during its subsequent spinning motion. EFC. | ||