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 the PH III, 25/30, and BENT 4¼ models.
| Identifier | ExFiles\Box 85\2\ scan0300 | |
| Date | 16th November 1936 guessed | |
| PH III | 25/30 | BENT 4¼ CLUTCH ARRGT. | G84357 | G57170 | G132099 PEDAL ARRGT. | F87352 | F61066 | GL{G. Linnett} 799 WT. OF FLYWHEEL & CLUTCH. lbs | 77 | 71 | 64 INERTIA FLYWHEEL & CLUTCH. lbs ins² | 2200 | 2005 | 1810 INERTIA DRIVEN PLATE lbs. ins² | 102.5 | 42.8 | 32.7 OVERALL PEDAL RATIO | 54 | 42.5 | 39 WORKING PEDAL TRAVEL | 5.0 | 3.4 | 3.7 FREE MOVT. OF PEDAL | .787 | .950 | .950 THEOR.L SEPARATION | .092 | .080 | .095 ACTUAL SEPARATION | .075 | .058 | .065 WEAR BEFORE ADJUSTMENT | .015 | .022 | .026 TOTAL WEAR ALLOWANCE | .125 | .125 | .104 CUSHIONING ON DRIVEN DISC | .030 | .030 | .030 EFFECTIVE DIA. FACINGS | 11.00 | 9.00 | 8.00 TOTAL THRUST POUNDAGE | 1932 | 1320 | 1368 THEOR.L PEDAL PR.{Percy H. Rose} CLUTCH ENGAGED | 39 | 31 | 35 TYPE OF FACING | No6 | MOULDED | WOVEN MAX. ENGINE TORQUE lbs. ft. | 356 | 190 | 208 WORKING μ | .19 | .19 | .23 CLUTCH PARTICULARS 7/L. Smith 4 x 36 RM{William Robotham - Chief Engineer} 250 | ||