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).
The wear of standard Bakelite contact breaker rubbing blocks on various cars.
| Identifier | ExFiles\Box 35\6\ scan 118 | |
| Date | 22th February 1924 | |
| EFC. FC.22. Feb. 22nd. 1924. WEAR OF STANDARD (BAKELITE) CONTACT BREAKER RUBBING BLOCKS. The contact breaker rubbing blocks on all available cars have been measured. It has been ascertained from the D.O. that the overall dimension of the block in position on the lever is .257" to .262". Allowing for fitting (which if anything tends to increase this dimension) .265" has been assumed as the thickness of the block and lever when new. In the case of the block fitted to 6GII, .265" was actually the maximum thickness as measured at the commencement of the 10,000 mile test, and the figures in connection with it may be regarded as the results of a definite test. The figures for 4GII and 7GII are of little value, as the exact number of miles run in the case of the former is unknown, while the rubbing block of the latter, after running, is larger than it should have been originally. | Car. | Assumed Thickness New. | Thickness measured. | Max. amount of wear. | Miles run. | Remarks. | |-------|------------------------|---------------------|----------------------|----------------|----------------------------------------------| | 7GII. | .265" | .264" | .001" | 1,450 | | | 4GII. | .265" | .250" to .251. | .015" | About 10,000. | No record of date when put on. | | 6GII. | .260" to .265" | .253" to .260" | .007" | 10,793. | Measurements actually made before and after running. | | 7GII. | .275" | .270" to .272" | .005" | 5,430. | | | ||