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).
Comparative table of clutch particulars for various car models.
| Identifier | ExFiles\Box 93\3\ scan0019 | |
| Date | 1st February 1935 | |
| SHEET (2) CLUTCH PARTICULARS MODELS: 20/25, BENTLEY, SPECTRECodename for Phantom III, WRAITH, BENTLEY TOTAL SPRING POUNDAGE: 20/25: 1240 BENTLEY: 1440 SPECTRECodename for Phantom III: 1330 WRAITH: 1350 BENTLEY: 1300 SEPARATION THEORETICAL: 20/25: .075 BENTLEY: .083 SPECTRECodename for Phantom III: .061 BENTLEY: .096 LOST SEPARATION FROM CUSHIONING: 20/25: .012 PRESSURE ON LININGS: 20/25: 25.8 BENTLEY: 24.9 SPECTRECodename for Phantom III: 26.7 WRAITH: 25.8 BENTLEY: 31.5 WORKING COEFFICIENT OF FRICTION: BENTLEY: .168 MAX WEAR BEFORE ADJUSTMENT PEDAL PRESSURE THEORETICAL: 20/25: 28.5 BENTLEY: 30.0 SPECTRECodename for Phantom III: 28.9 WRAITH: 24.9 BENTLEY: 31 ENGINE TORQUE: BENTLEY: 178 FABRIC DIAMETER: 20/25: 10.5 - 7.0 R = 4.37 BENTLEY: 10.9 - 6.7 = 4.4 SPECTRECodename for Phantom III: 13.5 - 9.5 = 5.75 WRAITH: 12.0 - 8.1 = 5.02 BENTLEY: 9.7 - 6.4 = 4.02 ACTUAL SEPARATION ALLOWING FOR LOSSES MEASURED EFFORT TO PUT CLUTCH OUT MEASURED EFFORT TO HOLD CLUTCH OUT FINGER RATIO: 20/25: 4.9 (43) BENTLEY: 5.5 (48) SPECTRECodename for Phantom III: 5.4 (66) WRAITH: 3.9 (55) BENTLEY: 4.8 (42) PEDAL TO THRUST BRG. RATIO: 20/25: 8.85 BENTLEY: 8.75 SPECTRECodename for Phantom III: 12.2 WRAITH: 14.0 BENTLEY: 8.75 PEDAL TRAVEL: 20/25: 3.2 BENTLEY: 4.0 SPECTRECodename for Phantom III: 4.0 ARRANGEMENT OF PEDALS: 20/25: F.60502 BENTLEY: N.SCH.4156 ARRANGEMENT OF CLUTCH: 20/25: N.SCH.3948 11" B&B BENTLEY: 11" B&B SPECTRECodename for Phantom III: N.SCH.4229 WRAITH: N.SCH.4313 BENTLEY: 10" B&B | ||