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).
Letter providing suggestions on the construction of magnet cores, specifically regarding leads, banding, and treatment.
| Identifier | ExFiles\Box 24\2\ Scan147 | |
| Date | 24th March 1921 | |
| M.Olley.- Sheet 2. March 24, 1921. wind your coils with bare enamelled wire. If you care to go into this question further I will be glad to talk this matter over with you and offer suggestions as to the construction of the magnet cores, etc. 3. LEADS. Our standard practice is to bring the lead out doubling the lead back on itself and twisting the two together. The insulation sleeving extends about 1" under the banding. We do this on all of our field coils used in automobile generators, and this construction will give you no trouble on 20 and 26 S.W.G. wire shewn on your prints. 4. BANDING. The coil should be banded with 3/64 or 1/16 torpedo twine. This is a strong, braided cotton cord, which we use on our standard product. Many coils are banded with ordinary book binder's cloth, but this is not as satisfactory as the torpedo.twine. 5. TREATMENT. The completed coil should be given two dips and bakes in Sterling varnish. In the dipping process, the coil is kept immersed until bubbling ceases, which is usually 20 minutes to one half hour. After this, it is drained and baked for 22 hours at 125°C. This process is repeated for the second dip.and bake. This varnish has no effect on the enamel on the wire. Enamelled wire coils should not be dipped in bakelite, as the bakelite destroys the enamel. However, there is no interaction between the bakelite micarta board in which the bakelite is thoroughly cured, and the enamelled wire which is wound on the spool. Please let me know if you desire any more information on this subject, as we are always glad to assist you in any of your problems. Trusting that the above will be of some service to you, I remain. Yours truly, (Signed) R.G.Thompson. | ||