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).
Speedometer drive particulars for the Phantom II and 20 HP models.
| Identifier | ExFiles\Box 50\4\ Scan316 | |
| Date | 28th October 1929 | |
| X.4308 28.10.29. X.4308. A.T. SPEEDOMETER DRIVE PARTICULARS. Phantom II. Road wheel revolutions per mile = 608.7 average or = 595 minimum. Speedometer drive gear ratios = 41/11 x 2/18 x 26/8 = 1.346 Speedometer drive revolutions per mile = 819 average or = 801 minimum. 20 H.P. Road wheel revolutions per mile = 660 Speedometer drive gear ratio = 50/11 x 2/16 x 20/10 = 50/11 x 1/4 = 1.136 Speedometer drive revolutions per mile = 750 EFC. | ||