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).
Remarks on sketched sparks, comparing two different gap types and their appearance from a magneto.
| Identifier | ExFiles\Box 63\4\ scan0022 | |
| Date | 26th May 1918 guessed | |
| -22- REMARKS ON THE SPARKS SKETCHED. The sparks are bluish white and the arcs and striations are mauve. On the A gap the sketches represent the effect of a continuous succession of sparks from the magneto. On the B gap each sketch represents what is ordinarily one spark i.e. each sketch is the result of one break. This was attained by adjusting the magneto speed until successive sparks were conveniently spaced round the periphery. Long and short gap sparks could thus be observed at the same time. In each sketch for the B gap the lower straight line represents the internal sharpened circular edge of the square disc, and the upper line represents the path of the rotating high tension point. Neither type of gap A or B reproduces exactly in a drawn out state the spark on a stationary gap. A rapidly revolving mirror would be the only way to do this. A does so probably better than B. There is windage in the A case which very largely blows the arc away from the spark. On the other hand, in case B the position of the gap is continually changing in such a way that a drawn out arc may give way to another spark e.g. sketch Nos. 14, 20, 26, 30, 32 etc., which would not happen on a stationary gap. Thus, the quantity of electricity following up the initial spark or sparks is manifested as an arc on the A gap, but may be manifested as further sparks on the B gap. Z.R.6 At 150 R.P.M. the quantity is greater at advance than at retard (pp 4,5) (This is on account of the large quantity | ||