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).
Calculations and specifications for 'Myth' hydraulic brakes.
| Identifier | ExFiles\Box 110\1\ scan0007 | |
| Date | 6th September 1940 | |
| 706 To Ev.{Ivan Evernden - coachwork} from Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby}2/ET.6.9.40. MYTH HYDRAULIC BRAKES. ==================== With regard to shoe dimensions, the projected sizes of 10.0 ins. diameter and 1.5 ins. wide, assuming a lining of 100°, give a ratio of laden weight to lining area of 27 lbs/sq. in, which is somewhat high compared with our normal maximum figure of 23 lbs/sq.in. A width of 1.75 ins. would bring it into line and reduce drum temperatures. For a 25 fb/sec² stop, the weight distribution calls for a front to rear braking ratio of 1.70, using a pedal pressure of 150 lbs. for a 100% stop, and a lining frictional coefficient of 0.4, the overall brake ratio will be 123.5 : If the tandem master cylinder is 1.000" diameter, we can use either: 1. Wheel cylinders of 3/4" and 9/16" diameter front and rear respectively, giving a brake ratio of 1.78:1, and a pedal leverage of 10.0" / 1.52", or 2. Wheel cylinders of 7/8" and 11/16" diameter front and rear respectively, giving a ratio of 1.62:1, and a pedal leverage of 10" / 2.15" . We should like to know why the handbrake could not work at a bisector similar to the type to be used on Rippletto. Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} | ||