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).
Brake system developments for public service vehicles from the Commercial Motor Transport Exhibition.
| Identifier | ExFiles\Box 179\1\ img110 | |
| Date | 21th November 1931 | |
| FROM E.{Mr Elliott - Chief Engineer} C. to S/W.R. F.C. & H.{Arthur M. Hanbury - Head Complaints} ORIGINAL 21 NOV 1931 E1/W21.11.31. X631 COMMERCIAL MOTOR TRANSPORT EXHIBITION. (CONTINUED FROM E1/W14.11.31. & E1/W16.11.31.) BRAKES. Brakes on public service vehicles operating under modern traffic conditions are called upon to perform continuous and heavy duty, and it is therefore desirable to observe the trend of development. A point of some interest is raised by the exhibit of Ransomes Sims & Jefferies of an interlocking device whereby the parking brake is applied whenever the service brake is used, thereby halving the unit load on the rear axle brake shoes. Increased life out of all proportion to the increased brake surface area is claimed, such as for example brakes used by the Bristol Tramways on electric busses running 63,000 miles and wearing only one third of the liner thickness. This is compared with 7 to 10,000 miles which is said to be the usual life of liners on public service work. Naturally one accepts these figures with a considerable grain of salt but if there is anything in it at all it indicates that there is a limiting value for brake shoe pressure beyond which the liner wear becomes increasingly rapid. This point has possibly been considered by Messrs Dennis on their new bus chassis on which there is not a square inch of brake drum surface not covered by brake shoe. They have adopted the well known sch. of arranging the 4 brake shoes in the same plane but the design work has been well carried out and the shoes are supported in such a way as to avoid any tendency to twist. With this sch. they obtain practically double the brake shoe area for a given drum width. Each shoe is 6.5" wide and the internal dia. of the drum is 17". Two are operated by pedal and two by hand. A Marelli servo coupled to a Lockheed hydraulic system is used to operate the 4 wheel brakes. (1) | ||