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).
Construction and specifications of Coil No. 3, with comparisons to G.II and 40/50 coils.
| Identifier | ExFiles\Box 45\4\ Scan129 | |
| Date | 2nd January 1923 | |
| X 4079. Hs.{Lord Ernest Hives - Chair}. 2nd January 1923. Coil No. 3 is made up as follows:- All moulden parts are made of "Mouldensite" which EFC. has proved to be stronger mechanically and makes a better insulator than either "Elo" or American Bakelite. The coil case is .500 deeper than the original - this allows us to make the core .500 longer, also we are able to get 300 turns of D.S.C. Wire .032" dia. along the core in four layers instead of six layers, as in the original. We have a .002" insulation between each layer of primary winding. The above alteration enables us to keep the secondary winding somewhat closer to the core, which is, I believe, desirable. The secondary winding consists of 21,000 turns of .004 dia. enamelled wire. We have taken advantage of some of the extra length of core and have spread the winding out and by getting more turns per layer have been able to get all the 21,000 turns on in about 45 layers instead of 60, which we have to do on the original. This, together with the extra room gained by using only four layers of primary winding and the alteration to the dia of case of .050" gives about .312 air space between the secondary winding and the case. This would seem to be ample. The above alterations to the coil have not been expensive; it has only meant a new plunger being made for the mould. I should mention that the H.T.Insert has a .050" coat of vulcanised rubber over it before being moulded into case, and that Wor.{Arthur Wormald - General Works Manager} gave me permission to make these alterations before I started on this job. For comparison I give you the winding of the original "G.II" coil and also the winding of the standard 40/50 coil. "G.II" Coil. Primary:- 300 turns of .036" D.S.C.Wire in six layers. Secondary:- 22,000 turns of .004" Enamelled Wire in 60 layers. 40/50 Coil. Primary:- 360 turns of .032" D.S.C.Wire in six layers. Secondary:- 21,500 turns of .004" Enamelled Wire in 60 layers. The air space in both coils is practically nil. | ||