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).
The American Bosch Induction Coil and the use of Bakelite and other insulating materials in distributors.
| Identifier | ExFiles\Box 61b\4\ scan0026 | |
| Date | 5th April 1921 | |
| H.R. 235a (100 T) (S H.{Arthur M. Hanbury - Head Complaints} 798. 10-12-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2947 X4275 Extract from Ov2/G5.4.21. April 5th 1921. X,1109 - Insulating Material. X.4275. American Bosch Induction Coil. With regard to the American Bosch Induction Coil, this consists of a laminated core of low hysteresis iron inside a fiber tube. The primary is wound with enamel wire with varnished linen between the layers, and the secondary of enamel wire with varnished paper between the layers. The enamel used on the wire is Tung enamel, of Chinese origin, made from cotton seed, we believe. It has high elasticity and dielectric strength and maintains these qualities indefinitely. The coil is jacketed about the middle with a copper plated jacket of low hysteresis iron, which extends to within about ¼" of each end of the coil, the magnetic gap formed between the ends of the core and jacket being sufficient for a quick magnetic break. The black tube surrounding the coil is Bakelite Micarta, and the end mouldings are of Bakelite. The ballast resistance is wound on a porcelain spool mounted on an asbestos washer. The coil is not impregnated, but is taped and varnished on the outside. The coils have been tested under a spray of brine and under all sorts of conditions of heat and moisture. X.800. Distributors. Bakelite cannot be safely used for the tracks of the rubbing type of distributors or for the post carrying the H.T. collecting brush on magnetos because once a spark passes on Bakelite it leaves a carbon track which is a conductor for subsequent sparks. For these positions it is necessary to use hard rubber without any lamp-black or other carbonaceous filling material or else to use the German stabilite or the hightensite of the American Bosch Company which is claimed to be a similar material. The American Bosch claim to have discovered a method of molding high-tensite for magneto distributors which they claim was not molded in the German Bosch magnetos at the time they took over the business. Contd. | ||