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).
Note on the effect of an insulated third point on magneto test spark gaps.
| Identifier | ExFiles\Box 63\4\ scan0025 | |
| Date | 26th May 1918 guessed | |
| (I) NOTE RE EFFECT OF INSULATED THIRD POINT Test spark gaps for magnetos are usually fitted with an insulated third point adjusted to nearly touch the insulated high tension point as in sketch:- [Sketch of a spark gap with three points labeled 'H.T. Point', 'Earthed Point', and 'Insulated point'. The H.T. point is connected to an 'H.T. Lead' and the Earthed point is connected to 'E' for Earth.] We have made trials to determine the effect of this third point. We cannot as a result of our trials come to any very definite conclusions. We have had cases (with the Bosch Z.R.6 and Bosch Z.A.2) in which the third point has had a decided and deliberate effect in assisting the spark to pass. That is to say, if without the point the conditions are such that a spark will not take place (or only take place now and again), the effect of bring the point up is to cause perfectly regular firing to ensue. An insulated piece of bare wire with one end projecting transversely towards the H.T. point has in some cases had the same decided effect, so also has the presence of an insulated conductor in the neighbourhood of the H.T. point, even at a greater distance than sparking distance; this was observed by using a screw driver. | ||