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).
Instructions comparing the sparking performance and order of merit for different Goshawk coils.
| Identifier | ExFiles\Box 45\4\ Scan039 | |
| Date | 12th October 1922 | |
| RR. 238 (300 Bks.) (SF 152. 6-11-18.) MP 197880 ROLLS-ROYCE LIMITED. INSTRUCTIONS. 3. Oct 12th 1922 To E.F.C. Order No P.B. 58 Customer's No. X 4079 sparking performance of the coil; it will also make the coil reliable. i.e. enable it to maintain on the car, any performance it gives, when new, on the test bench. Using their maximum regular sparking gaps as a basis of comparison, the order of merit of Goshawk coils, is now as follows. Coil | Max. gap. | Remarks. + B. | 6.8mm | With 32" ballast. X1 | 6.5mm | = Standard performance. + SG{Arthur F. Sidgreaves - MD}1+SG{Arthur F. Sidgreaves - MD}2 | 6.3mm | With 25" ballast. X2 | 6.0mm + average production coil. | 5.2mm | With 32" ballast. Signed C.H.R. This Sheet must be filed on completion of the work. | ||