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).
Angular off-set of a battery ignition contact breaker arm, with a diagram and comparison to Bosch and Delco-Remy designs.
| Identifier | ExFiles\Box 61b\1\ scan0017 | |
| Date | 17th February 1927 | |
| To R.{Sir Henry Royce} from EF. c. to BJ. RG.{Mr Rowledge} Hs.{Lord Ernest Hives - Chair} BY EFC. X4041 E1/M17.2.27. BATTERY IGNITION. X.4041. With regard to the angular off-set of the contact breaker arm we have never considered any other line but the one passing through the pivot centre, and also the centre of curvature of the rubbing block. We have set out the Bosch and Delco-Remy proportions as accurately as possible and the measured angles of off-set are 25.5° and 26° respectively. A print is attached of the RR. contact arm arranged for 25° off-set for experimental trial. This has been sent to Derby for criticism, and with their agreement should be put on trial forthwith. So far as we can see the change of velocity of the make is in direct proportion to the linear displacement of the cam due to the off-set, and amounts to about 8%. By squaring the velocities it appears that the impact of the points would be reduced to about 85% of the present blow. The full available stroke of the rocker at the points is less than before - .049" instead of .057" - somewhat spoiling the purity of the test, but it is still more than double the gap to which the points are usually adjusted, e.g. .017" to .021", in fact it is more what we should expect it to be relative to the gap. E.{Mr Elliott - Chief Engineer} | ||