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).
Use of alloy steel versus carbon steel for Bentley contact breaker springs and issues with tempering.
| Identifier | ExFiles\Box 3\4\ 04-page349 | |
| Date | 22th June 1933 | |
| E.{Mr Elliott - Chief Engineer} Lacy c. Hs.{Lord Ernest Hives - Chair} c. He/Plt. BY.{R.W. Bailey - Chief Engineer} 2/G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 22.6.33. BENTLEY CONTACT BREAKER SPRING ---------------------------- Referring to E.8/HP.21.6.33. the production of a ribbon spring of this type in our special alloy spring steels is a very expensive and difficult process, and in my opinion is not justifiable. The reason for the use of the alloy steel is not the number of vibrations but purely a question of maximum stress, and I do not consider that the stress in the contact breaker spring need be such as to demand the very much increased cost of an alloy spring steel. Personally, I am quite satisfied that we can obtain a contact breaker spring in carbon steel made by the right people and in the right way which will function satisfactorily without failure. The springs which have been complained of have not broken, but apparently were on the soft side in tempering i.e. the tempering temperature had been carried too high. There is one other factor which has some slight bearing on the case viz. that a badly tempered spring, that is a spring tempered for too short a period tends to retain internal stresses, and this aspect of it is being taken up with the makers. The foregoing is a correct view of the situation, as steel does not soften as a result of work, but as you will appreciate tends to work harden. BY.{R.W. Bailey - Chief Engineer} | ||