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).
Ignition contact breaker proportions and safety settings to prevent engine reversal.
| Identifier | ExFiles\Box 37\1\ scan 031 | |
| Date | 4th May 1918 | |
| To EPC. From R.{Sir Henry Royce} -2- RB{R. Bowen}/C4.5.18. Contd. because the secondary current at slow speeds would appear to have enormous energy, owing to the large current at the time of break. Previously we arranged for a 66% make and 33% break, but I think we should now work for 75% make and 25% break, with plus and minus 5% for wear. We find that for safety of not running backwards when starting, the following points must be correct:- 1st. preferably a jump spark distributor of ample diameter. 2nd. advance of contact maker and distributor together, as arranged in car ignition, or by controlling the drive. 3rd. ample retard to make up for back lash in gearing. 4th. distributor set to be only just opposite proper contact at the time of break. 5th. short duration of break. Kindly test the following proportions:- [Handwritten diagram of a cam and follower with the following annotations:] Above: Pitch of contacts Left: 3/8 Right: 1/4 Pointing to the right: direction of rotation & position when contact maker breaks ratio of contact make to break 3/8 contact make 5/8 This seems perfectly safe and simpler than the Delco Liberty scheme. Kindly prove this and adopt these conditions on 49-GB. which engine should run to 3,000 r.p.m. R.{Sir Henry Royce} | ||