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).
Suggested specification for a 28 cwt. car's braking system.
| Identifier | ExFiles\Box 110\1\ scan0002 | |
| Date | 28th December 1935 guessed | |
| COPY. As from - 11, Manor Place, Oxford. My suggested specification for your 28 cwt. car is as follows :- Brake Drums - 10 1/4" internal dia. Linings - 1/4" thick 2 1/4 wide. Front brakes - Girling 2 leading shoe, only trailing shoe special shoe, leading shoe standard. Internal Hydraulic wheel cylinder 1 1/8" internal dia. (Design for 1 1/4" cylinder in case of need). Rear brakes. - As front, only mechanical wedge. Linkage. - Pedal normal, operating balancer similar to SCD. scheme made for 7.B.V. Pedal ratio to rear 16 : 1. Pedal ratio to front 24 : 1. Hand brake to rear 30 : 1. Master cyl. 1" dia. (I think this has enough capacity) Reasons & Remarks for this specification :- Brake Drums 10 1/4". This to accommodate linings 1/4" thick instead of usual 3/16". I do not like the idea of coming down from 12" at the same time as we throw away the zervo but accept it as inevitable. We ought to realize that on B.V. we get an increase of pedal effort in 14/3 ratio of 5 to 1, and we have to cope with this loss at the same time as we come down in drum diameter. Two Leading Shoe Brake. There is no hope of getting a satisfactory brake in view of the loss mentioned above unless we use the 2.5 : 1 energizing effect of the 2 LS brake. We have run the Bendix 2 LS brake some distance on 6.B.V. rear and it has done quite well. I am at present suggesting the Girling set up as more suitable for us but this point is immaterial. It is unfortunate that we never got 7.B.V. running before the war. Shoes 2 1/4" wide etc. I suggest that when using a "wrapping" brake that we shall get no satisfaction unless the surface temperature is kept down to a a minimum and the best way to do this is to use a wide shoe. Here there may be a difficulty with New Hudson who think that big cars ought to have large diam. drums, i.e. they increase width and diam. together. | ||