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 test field winding for a Phantom III dynamo.
| Identifier | ExFiles\Box 168a\3\ img493 | |
| Date | 28th April 1938 | |
| To HPS.{Horace Percy Smith - Experimental Factory Mgr} c. Rm{William Robotham - Chief Engineer}/RC.{R. Childs} BY/RD.2/B.28.4.38. 6142 PHANTOM III DYNAMO - FIELD WINDING. In order to obtain a field winding having a resistance of about 6¾ ohms, will you please make up, one set of field coils having 250 turns per coil of 20 S.W.G. (.036) D.C.C. Copper Wire, and being similar to D.76219 in all other particulars. Rm{William Robotham - Chief Engineer}/RC{R. Childs} will have for test one of the 6 production dynamos instructed in BY/RD.10/B.28.2.38. The above field coils should be fitted to this machine for a comparison test. The material required is :- ¼ lbs. of 20 S.W.G. (.036 dia). D.C.C. (Special 6/7 mils) Copper Wire. 15 yds. of 12 mm. x .005 Egyptian Tape. D.70710 - Cable Eye. 2 off. This is all production material. We understand that a field winding of this gauge, but having too high a resistance, has been tried in the past and gave a 1½% increase in cutting-in speed. This field winding will be much easier to assemble to the magnet case than the present standard winding. BY/RD. | ||