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).
Distributor timing specifications for a Watford IS12 Magneto No. 83133.
| Identifier | ExFiles\Box 43\4\ Scan060 | |
| Date | 9th February 1927 | |
| X4021 9.2.27. WATFORD IS12 MAGNETO No.83133. DISTRIBUTOR TIMING. Quantity. | Relative dimension. | Absolute dimension. ---|---|--- Pitch. (P) | 1.000 | .753" Make ratio (M) | .578 | .435" Range. (R) | .167 | .125" Forward overlap at advance. (Fa) | .044 | .033 Forward overlap at retard. (Fr) | .211 | .158 Brush + segment (B+S) | .558 | .420 Backward overlap at advance. (Ba) | .092 | .069 Backward overlap at retard. (Br) | -.075 | -.056 Segment. (S) | .266 | .200" Dia. of distributor. (D). | 3.820 | 2.875 Distance between leading edge of brush (Main) and leading edge of trailing brush. | 1.202 | .685 Width of trailing brush. | .226 | .170 Contd. | ||