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).
Piston knock issues with aluminium pistons and the resulting customer policy.
| Identifier | ExFiles\Box 35\2\ scan 099 | |
| Date | 22th August 1919 guessed | |
| Contd. X. 2748. 2. of clearance so that it is impossible to expect that these slack pistons will not knock. Everyone on the Technical side at least, knew that with aluminium pistons we should have to adopt a different policy with our customers to what we have done in the past. In the past we have trained our customers to try and detect the least knock and have willingly fitted new pistons when the least sign of a knock has been heard. Unless a different policy to that is adopted, aluminium pistons are impossible. It was in order that the sales Dept: should be fully aware of this change and what they are to expect that we demonstrated to Mr. Northey the conditions under which the knocks would be manifest. An owner of an old R.R. Car will certainly complain of knocks in his new car but we think if piston knocks are intelligently explained to him, in most cases he will be quite happy. We admit that we had hopes based on certain pistons which we ran on 49- GB that we should get less piston knocks than that we are experiencing on the new cars. We hoped they would be much better than those in 7-CA. There was an alteration made on the pistons since those which we were so pleased with on 49-GB. the alteration is that the rings were placed lower down. Putting the rings lower down robs the piston of some of the fitting portions which we have always found was necessary to avoid knocks. The rings being lower give us advantages in other directions. We shall (with the rings high up. We are also testing some pistons) be traying tomorrow a set of pistons made from a different alloy which Mr. Hall says will not expand nearly so much as th | ||