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).
Tests comparing Delco and R.R. distributors, focusing on plug gaps and ignition performance with oxidised plugs.
| Identifier | ExFiles\Box 162\2\ img014 | |
| Date | 27th March 1939 | |
| Mr.1/MG.27.3.39 (continued) - 3 - oxide from electrodes. In further tests in connection with plug gaps, care was taken to avoid altering the condition of plug electrodes. Reducing gaps to .025 on an oxidised set of plugs effected a 75% improvement. Reducing gaps to .020 overcame the trouble. Re-setting gaps to .030, misfiring recurred. Fitting a Delco distributor effected a complete cure with .030 gap, using oxidised plugs. Reverting to R.R.distributor, trouble recurred. These tests were repeated several times, and conclusive-ly proved that the Delco ignition is superior to R.R. with large gap plugs in an oxidised condition. Comparing the two distributors, the differences are: (1) Delco has a make/break ratio of 70-30 R.R. " " " " 55-45 The increased time of make on Delco is obtained by using a 3-lobe cam, using two contact levers. The R.R.distributor has a 6-lobe cam with one contact lever. (2) Delco has a .024 air gap between rotating, and fixed electrodes, using a Monel Metal Rotor blade R.R. has an air gap in the region of .005, using a brass Rotor blade. We endeavoured to increase the make period on the R.R.distributor, by reducing the contact area of rubbing block, in conjunction with a .010 gap at low tension contact points. This combination gave a 30% improvement. By means of an adjustable Rotor blade we were able | ||