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).
Inspection report on a U.S.A. Bosch Ignition Coil, type TC.30, detailing its construction and the inability to find a cause for its partial failure.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 109 | |
| Date | 19th May 1927 | |
| To E.{Mr Elliott - Chief Engineer} from EFC. C. R.{Sir Henry Royce} U.S.A. BOSCH IGNITION COIL TYPE TC.30. We have now completed our opening up and inspection of the American Bosch coil referred to in our EFC1/T17.5.27, and we are sending the parts along to you for your inspection. The following is the text of my assistant's report :- "This coil as described in our previous report WB.{Mr Brazier/Mr Bell}109 has now been opened up for inspection. We were unable to discover the cause of the partial failure as probably any evidence of sparking over was spoilt by the sealing compound running when releasing the coil by heating it. The arrangement of the core is interesting. An iron sheath .020" thick encircles the outside of the windings and is part of the coil magnetic circuit but owing to the fact that there is a large air gap between this sheath and the core, it is at low tension. It is made at each end in comb fashion apparently to avoid eddy currents and possible to help radiate the heat generated in the primary. The windings are wound unconventionally on to the core, the H.T. end of the secondary coming out next to the core itself; a large porcelain insulator forms a pedestal for the core and windings when in position in the sheet tin case. The primary is wound with 21 SWG. enamelled wire. Both windings are paper insulated throughout, three layers of .0015" waxed paper insulating each secondary layer. U.S.A. Bosch follow usual American practice by running a bitumen or pitch sealing compound into the metal coil case to seal the coil into position." We hope you are taking steps to have the other coil returned to us. EFC. | ||