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).
Tests on brake inefficiency for Phantom cars, comparing different brake drum and shoe configurations.
| Identifier | Morton\M19\ img163 | |
| Date | 5th May 1931 | |
| ORIGINAL To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/GML. c. to Sg.{Arthur F. Sidgreaves - MD} Hor. c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to Hy.{Tom Haldenby - Plant Engineer} Ha/GWH.{George W. Hancock - Head Chateauroux}4/KT.5.5.31. X4117 Y7366 We have been receiving a number of complaints from Owners, of the inefficiency of brakes on Phantom cars after several applications of the brakes. We have carried out numerous tests using Cast Iron ribbed and Steel drums, both front and rear, and various makes of brake linings using both the narrow and broad brake shoes on the rear. We found from these tests that the cause of the inefficiency complained of, is due to the narrow rear brake shoes quickly losing their efficiency through heat. This is caused by the smaller area of braking surface with a consequent higher unit pressure. We found that equal efficiency could be maintained with the narrow rear brake shoes when using the ribbed brake drums. The drums in this case keeping the brakes cooler. We also found that equal efficiency could be maintained by using the broad rear brake shoes when using the 40% stiffer plain drums, the reason being that more area of brake is in contact with less unit pressure. The front brakes are not affected to the same extent as the rear, and we did not find any gain by the use of ribbed drums. The following figures of distance in de-acceleration by the application of the brakes from 70 MPH, making seven consecutive tests shows the proof of the above statements. 40% stiffer rear plain brake drums Narrow type rear brake shoes. Front brakes standard. Distance to pull up from 70 MPH. to 10 MPH. 1st. test cold 305 ft. 7th. test hot 429 ft. a loss of 124 ft. 40% stiffer rear plain brake drums Broad type rear brake shoes Front brakes standard. Distance to pull up from 70 MPH. to 10 MPH. 1st. test cold 260 ft. 7th. test hot 270 ft. a loss of 10 ft. Ribbed rear brake drums Narrow type rear brake shoes Front brakes standard. Distance to pull up from 70 MPH. to 10 MPH. 1st. test cold 244 ft. 7th. test hot 260 ft. a loss of 16 ft. Ferodo bonded brake linings were used on the rear brakes and Ferobestos brake lining on the front for the tests. | ||