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).
Comparative analysis of ignition coil and contact breaker performance at 12 volts.
| Identifier | ExFiles\Box 52\3\ Scan342 | |
| Date | 25th September 1917 | |
| 12 Volts. 27|25|9|17 K2814 Condition | Amps (Short circuit, 2000, 300) | length of wire to contact | length of spark (30 Revs, 2000) | Sparking at contact / HT spark (300 revs, 2000 revs pm) ---|---|---|---|--- RR coil RR contact breaker, with Remy resistance in series with primary wire. | 5.2 | 2.2 | 2.9 | 12" | 13/32" | 9/16" | slight | bad (moderate) ditto | 5.2 | 2 | 3 | 5 ft. | 3/8" | 9/16" | slight | bad (moderate) RR coil Remy contact breaker Remy resistance in series with primary wire | 5.2 | 2.8 | 3.4 | 5 ft | 13/32" | 15/32" | slight | very bad RR coil Remy contact breaker Remy resistance in series with primary winding | 5.2 | 2.3 | 3.4 | 12" | 3/8" | 17/32" | moderate | very bad The high amperage in 3 & 4 test or previous test agreed with RR coil and Remy contact breaker is due to the current short circuiting across the points the gap not being great enough. To prevent this with the heavy current for running the engine at about 500 revs the amps vary from 6.5 to 8.5. When using 6.5 amps the spark is OK but when using 8.5 amps there is no spark due to the current jumping across the make & break. This is what happens when running at high speed. The gap varies on each break as follows Remy .032 .027 .025 .032 .034 RR .027 .025 .023 .025 .020 Difference in lift of contact with points just set to touch RR .045" Remy .077". 3 lbs pull required to lift contact just clear of point RR 1 1/2 lbs required to lift contact just clear of point. Remy contact points are made of steel and pit very dirty but do not fuse, a bluish coat covers the points. [Left Margin Text]: R.R. 166 (10 m) ISC 574. 25.2.16 E.P. 1340 | ||