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).
Load and pressure of Goshawk dynamo brush springs and suggesting improvements.
| Identifier | ExFiles\Box 50\5\ Scan187 | |
| Date | 19th June 1923 | |
| X4883 To EFC. from R.{Sir Henry Royce} R2/M19.6.23. 4883 X.8676 - GOSHAWK DYNAMO BRUSH SPRINGS. With reference to these we find (on 5-G.II) that on measuring the load produced by these springs on the carbons by means of a spring balance, that it measures approximately just under ¼ lb. per spring. We have also measured the load produced by the brush springs on the Bosch dynamo, and this works out to be an intensity of approximately 4.25 lbs. per sq.in. of carbon area, whereas the intensity of pressure on the Goshawk brush is in the neighbourhood of half this. (The Bosch dynamo brushes it should be noted are of a particularly soft grade of carbon). We suggest that in view of the recent statement made by you that the brush wear on the Goshawk dynamo has been found to be .001 per 20,000 miles, that experiments might be carried out with increased brush spring pressure, to see whether this is advantageous from a point of view of reliability, and increased efficiency from a point of view of current carrying by the brushes, without undue wear. I understand we are now in a much better position because of: (1) Improved position (less liable to spark). (2) Removing the copper coating. (3) Better and freer fitting brushes. now(4) More reliable and greater spring pressure. R.{Sir Henry Royce} | ||