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).
Instruction sheet detailing the measurement of the safety gap on a Watford aero magneto type IS12, which was found to be too small.
| Identifier | ExFiles\Box 43\4\ Scan026 | |
| Date | 9th December 1926 | |
| X4021 ROLLS-ROYCE LTD. INSTRUCTIONS. To: E.F.G. Order No.: WB{Mr Brazier/Mr Bell}117 Customer's No.: X 4021 9 - 12 - 1926 Safety gap on Watford aero magnetos type IS12. In a previous report on these magnetos (WB{Mr Brazier/Mr Bell}104/23-9-26) it was observed that regular sparking externally could only be obtained on 4.5mm to 5.0mm gaps in air, if these gaps were increased sparks occurred internally at the safety gap. It was then suggested that the safety gap on these magnetos was too small. We have now measured the safety gap on one of these type magnetos (NO 83134) and find it to be only 7.8 mm. This we consider too small for a jump spark magneto. Signed: contd This Sheet must be filed on completion of the work. | ||