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).
With diagrams proposing alternative construction methods for an ignition coil.
| Identifier | ExFiles\Box 178\3\ img048 | |
| Date | 28th January 1932 | |
| HS.{Lord Ernest Hives - Chair} E.{Mr Elliott - Chief Engineer}) FROM R.{Sir Henry Royce} BY.{R.W. Bailey - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) C to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} RG.{Mr Rowledge} DA.{Bernard Day - Chassis Design} IGNITION COIL. R2/M24.1.32. Sent from WW. 28.1.32. X6058 I do not think we can very conveniently roll up a core for the above from sheet metal. It occurred to me that an easy way would be to provide cut and flat strips of stalloy or suitable low hysterisis steel or iron of varying width, starting with say .250", increasing by .0625 to size required, thus ;- and use a few narrow ones to finish approx: circular. These would all fold down to make hedgehog type, and the complete coil go inside the tube of insulating materials, outside of which is the iron jacket. Brown - secondary winding. Red - primary winding. Blue - iron core and jacket. Black - insulation. Tube folded from sheet metal end split to reduce eddy currents. Several proportions of core area should be tried to get the minimum turns of secondary winding - i.e. quantity of expensive wire especially when wound. It has also occurred to me that we might get much less winding with short magnetic circuit of larger section consisting of magneto, armature like stamping, and rings, thus:- Insulating tube probably very thin - of good materials. Perhaps not very convenient for winding but is done on the most general pattern of magneto, and is a very good way of making a magnetic circuit of any proportions of air space etc, and the laminations are very good - i.e. without eddy currents. R.{Sir Henry Royce} | ||