Revision to the Wraith II Servo design, comparing its specifications with other contemporary models.
| Identifier | ExFiles\Box 9\4\ 04-page02 | |
| Date | 27th August 1936 | |
| Koot 641 Martindale. 79 E {Mr Elliott - Chief Engineer} /HDY. {William Hardy} 1/HP.27.8.36. C.E. Des. RMC. Hs {Lord Ernest Hives - Chair} /Rm. {William Robotham - Chief Engineer} Wraith II Servo. We send herewith N.Sch.4884 showing a revision of N.Sch.4309, the original design for the Wraith servo. The revision is mainly necessary because various features on the original design are now out of date when compared with Phantom III practice. The diameter remains unchanged at 4.25 mean diameter. That for the 25/30 and Bentley is 4.0". The area for the Wraith is 7.0sq.in against the 25/30 and Bentley of 8.0sq.in. The calculated torque multiplication allowing a coefficient of friction of .3 and with 45° cams is 2.7. The corresponding figure for the 25/30 which now has 35° cams is 2.5 and for the Bentley which still has 45° cams 1.75. The servo speed is 1/10.5 engine speed against 1/8 for the 25/30/Bentley. and E {Mr Elliott - Chief Engineer} /HDY. {William Hardy} | ||
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).