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).
Design and functionality of a multi-position electrical switch, comparing a drum-type design to existing contacts.
| Identifier | ExFiles\Box 168a\2\ img098 | |
| Date | 14th March 1933 guessed | |
| (2) It is possible that the switch would be rather a deep affair. The handle would have to be insulated. It looks as though rings or segments would be threaded on and cramped endways, using bakelite micarta insulation tube and washer, and the currect brought to one of the rings to supply current to all and other contacts. It does not look as though we could have much more than these two contacts on a ring. The reason I don't favour the present contacts is that they are not very flexible, and require very careful setting, whereas the drum type suggested has a large movement more like a dynamo brush, and when off their segments drop say 3/16" on to a rigid stop so that the wear for adjustment one has only to alter the stop, and to see there is plenty of elasticity in the contact finger. Whether the joints are pin joints with the flexible, or whether it is a springy piece of copper with or without a pin joint is a matter of design, but it will be seen that the friction is not great, and easily controlled, and the sparking does not take place where the contact occurs, and the notch plate can have powerful control over the friction of the contacts, very different to the Bosch scheme. Controller type switches are usually built with contact fingers clamped on a square bar, covered with a bakelite square tube with washers between, I imagined that if we could do with 6 positions (5 on, 1 off) we could use 3 such bars. These could carry the back bearing, and also carry contact fingers on any of them. Assuming you wish to cut off all accessories at 'O' you would get: (a) 1 finger for accessories. (b) " ignition, charge, starter. (c) " side and tail. (d) " head. (e) " supply of current. 5 rings or segments, and we might be able to save one segment by having an extra finger. The actual electric contact might be about .2 wide or less, and separated by a 1/16" takelite washer. The washers on the barrel might have copper centre like a gasket to conduct the currect from end to end of the barrel. The design of contact finger should be quite a little work of art, and easy to make thoroughly efficient. R.{Sir Henry Royce} | ||