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).
Instructions to modify an S.S. main and auxiliary switch unit by increasing the carbon spring set to prevent sparking.
| Identifier | ExFiles\Box 64\4\ scan0240 | |
| Date | 15th April 1929 | |
| RR 23B {150 BKS.} (DB{Donald Bastow - Suspensions} 461-8-12-24) MP 306975 X.7655 ROLLS-ROYCE LTD. INSTRUCTIONS. 15 - 4 - 1929 To E.T.C. Order No. WD{Mr Wood/Mr Whitehead}54 Customer's No. S.S. main and auxiliary switch unit As a result of testing a unit with the brass winding cheeks fitted we were of the opinion that the flat carbon arm spring could have a much larger set. This would help to prevent sparking at the coppers due to the inertia of the carbon arm. Accordingly we fitted a carbon spring having a set of 10° instead of 5°! This modification considerably increased the spring pressure but did not interfere with the satisfactory operation of the switch and we would recommend this feature or modification as desirable. Signed H.E.W. This Sheet must be filed on completion of the work. Recommended to and noted for inclusion by by / R.D. | ||