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).
Graph of maximum gap-speed curves for five different special ignition coils.
| Identifier | WestWitteringFiles\D\April1920\ Scan7 | |
| Date | 13th April 1920 | |
| MAXIMUM GAP-SPEED CURVES for SPECIAL COILS. USING 12 VOLT BATTERY AND R.R. CONTACT BREAKER WITH SINGLE PLATINUM POINT SPARK GAP. I CURVE No. 1 - COIL No. S10. (x) " " 2 - " " S12. (o) " " 3 - " " E14. (⊗) " " 4 - " " E18. (●) " " 5 - " " 149* (☒) (*STANDARD COIL) GAP. (Inches) .5 .4 .3 .2 .1 0 R.P.M. 200 400 600 800 1000 1200 1400 1600 1800 ① ② ③ ④ ⑤ Handwritten: PCSg 30/3/20 E.7.C 13/4/20 | ||