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).
Calculation of B.V brake pedal ratios for different mechanical and rationalised systems.
| Identifier | ExFiles\Box 121\1\ scan0372 | |
| Date | 29th October 1940 | |
| 206 To Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}3/ET.29.10.40. 1029 B.V BRAKE PEDAL RATIOS. ------------------------- Taking a body weight of 3920 lbs. (weight of 9.B.V.) for a 32.2 ft/sec² deceleration, total force required at shoe tips is W/2 x R/r = F/ F = (3920 x 29.0) / (2 x 12.25 x 0.36) = 12950 lbs. 1. ALL MECHANICAL PRODUCTION SYSTEM. Theoretical ratios. Total Front Brakes = 72.1 P. Total Rear Brakes = 47.55 P. Total brakes = 120 P. Ratio F/R = 1.51 Allowing for efficiencies of 57.5% on the front and 67.5% on the rear these figures become: Front Brakes = 43.3 P. Rear " = 33.3 P. Total " = 86.6 P. Ratio F/R = 1.29 Thus for a 32.2 ft/sec² stop we require a pedal pressure of 12950 / 120 = 108 lbs. theoretically or 12950 / 86.6 = 149.5 lbs. actually 2. RATIONALISED SYSTEM AS EXEMPLIFIED BY 12.B.V. Theoretical ratios. Total Front Brakes = 77.7 P. Total Rear Brakes = 60.7 P. Total Brakes = 138.4 P. Ratio F/R.{Sir Henry Royce} = 1.275 Allowing for efficiencies of 70% front and 67.5% rear, these figures become Total Front Brakes = 54.3 P. Total Rear Brakes = 41.0 P. Total = 95.3 P. Ratio F/R.{Sir Henry Royce} = 1.32 | ||