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 improvements for the 'SS' starter motor.
| Identifier | WestWitteringFiles\T\2July1928-December1928\ Scan201 | |
| Date | 10th November 1928 | |
| HS.{Lord Ernest Hives - Chair}) FROM R.{Sir Henry Royce} EFC.) C. to B.I. WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} 'SS{S. Smith}' STARTER MOTOR. This was better in many ways on EAC. 7. than our present standard, and is not difficult to increase its margin of safety. (13:1) (handwritten) (1) Gears have shewn us that EAC.7. being 16. to 1. is quite as far as we can go. (2) It is probable that both gears should be hardened, and here is a job for nitrifying (underlined) hardening of the F.W. - (soft wheel gears may get embedded with road grit.) (3) The pinion increases in size when corrected for interference. This has been done in EAC. 7. (4) It is easily possible to get 25% more axial contact- i.e. 5/8" width of gear on flywheel, 1/2" width of pinion. EAC. 7. overmeshes into gear by 1/8". (5) Central oiling scheme may drop a little oil on the starter motor pinion. Refer some of these points to the Bosch system, which is very similar. MOTOR. (underlined) Efficiency can be increased if not already done by the use of tape wound armature and field, (must fill space available with copper.) ✓ (handwritten checkmark) I am quite in agreement with lengthening the core 3/4". End thump was not bad, hardly noticed on EAC. 7. Contact for main switch might be tried later. Some form of spring for the final position, but it must give a position which is permanent to ensure correct engagement. The load on starter teeth is very small compared with back axle gears and gearbox practice, so the wear must be want of hardness or cleaner lubrication. Now hard surfaces are not so dependent upon clean lubrication we can improve both, as well as the area. When the armature is in running position, the air space should be as small as possible so that say 4 1/2 turns per pole is sufficient to give moderate saturation to the iron circuit. (1) | ||