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).
Production issues and helix errors found in Wraith engine timing gears.
| Identifier | ExFiles\Box 6\6\ 06-page296 | |
| Date | 30th August 1937 | |
| HPS.{Horace Percy Smith - Experimental Factory Mgr} from Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} c. to HY.{Tom Haldenby - Plant Engineer} c. to REG. Handwritten: 600 chassis 115's Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer}4/R.30.8.37. WRAITH TIMING GEARS. It should be easier to produce quiet timing gears on the Wraith engine unit than on any unit we have previously produced owing to having (a) three gears only (b) Fabroil camwheel, and (c) in the case of No.5 unit, soft metal gears and 41° helix. Despite all these design improvements the results in practice have so far been very bad, and in no case have the gears been up to production standard as first assembled. On No.2 unit the gears had a very bad bedding, and when checked on RHC{R. H. Coverley - Production Engineer}/Mr. Clark's set up the cam-wheel showed a helix error of 0.0020 in 1.080 face width. Similarly, on No.5 unit with soft metal gears, the bedding was very bad and measurements gave the following errors:- Dynamo pinion - Helix error -0.0012 in 1.080 Camwheel " " -0.0017 " 1.080 Crank pinion " " +0.0007 " 1.080 As we have previously stated, we consider the maximum helix error should be 0.0003 per inch width of gear. In view of the very large errors on No.5 unit, and as these cannot be attributed to hardening distortion, it would appear that there must be something wrong with the hobbing machines. So far as timing gear noise is concerned, no useful purpose will be served by building up new units with inaccurate gears. Will you please make sure that future timing gears are within the limit of 0.0003 per inch width for helix angle, and have 0.001 to 0.003 pitch line backlash. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} | ||