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).
Investigation into the seizing of a contact breaker lever on a Bentley chassis due to its Bakelite bush.
| Identifier | ExFiles\Box 61b\1\ scan0179 | |
| Date | 16th December 1933 | |
| E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. c. to Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} SEIZING OF CONTACT BREAKER LEVER ON BENTLEY CHASSIS. Following a reported failure of a contact breaker lever on one of our trials cars we have investigated the cause of this. Two standard levers were obtained from production with the standard pin. In each case the clearance was only approximately .0005". One of these levers complete with its Bakelite bush was immersed in water for 24 hrs, and the other one was baked at a temperature of 80ºC. for 24 hrs. At the conclusion of these tests both levers were tight on the pivot pin but in the case of the one immersed in water, after allowing it to dry in air the lever freed itself on the pivot, whereas the lever which had been baked remained tight. It appears therefore that these lever bushes whilst being slightly hygroscopic are not permanently so, but the effect of temperature on the car would appear to have a shrinking effect on the bush. It would therefore be a good plan to put all production levers in the oven overnight before fitting them to the distributors, in order to cure the bakelite compound. This is done on big bakelite mouldings, where it is known that Bakelite has to be properly cured under temperatured in order to make it absolutely stable. At the same time we consider there should be ample clearance at this point on magnetos. The usual clearance is at least .002". | ||