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).
Technical discussion on brake system design and calculations for the Myth and Rippletto models.
| Identifier | ExFiles\Box 121\1\ scan0317 | |
| Date | 13th September 1940 | |
| -2- Ev.{Ivan Evernden - coachwork}4/JH.13.9.40. During the discussion on wedge efficiency it was suggested by Mr. Parnell that this should not be below 80%. It was not considered that this factor should be justly blamed for troubles on the front brakes of 8 cylinder cars of the Senior Range. The Rippletto brake drums will be 11" in diameter and the shoes 1¾" wide. The drums will exceed 11" by virtue of increased lining thickness if this is used. MYTH. It was agreed that Myth should have the same hydraulic equipment as Rippletto and the same pipe line pressure. The difference in weights being provided for in the diameter of the drum, and the width of the shoes. The calculation to arrive at the drum size is as follows :- Car loaded 26 cwts. or 2900 lbs. 5.5 x 16 tyres. Rolling radius 13" Retardation per wheel 750 lbs. approx. Shoe tip pressure assuming ¾" dia. wheel cylinder 550 lbs. Retardation at drum 2200 lbs. This gives the drum approximately 8.9" dia. Mr. Parnell stated that he recommended the standard 9" drum with 1.5" wide shoes, the drum diameter being slightly increased to accommodate the thicker lining. Mr. Parnell will investigate the use of the plate lever hand brake operation, but it was tentatively agreed on his recommendation that we should use the latest bisector. GENERAL. It was agreed that we would supply to Mr. Parnell layouts of the front and rear brakes for both Myth and Rippletto, the Rippletto to come first. Mr. Parnell will send us as soon as they are available arrangements of the master cylinder and the wheel cylinders including the bisector so that we may complete our schemes for both Myth and Rippletto. Ev.{Ivan Evernden - coachwork} | ||