Trial of a four-shoe brake on the Wraith front axle to solve brake squeak problems.
| Identifier | ExFiles\Box 7\7\ X 606 Brakes-page097 | |
| Date | 13th January 1938 | |
| To Hs. {Lord Ernest Hives - Chair} from RM {William Robotham - Chief Engineer} /AFW. c.c. SG. {Arthur F. Sidgreaves - MD} c. By. {R.W. Bailey - Chief Engineer} c. Da. {Bernard Day - Chassis Design} e. {Mr Elliott - Chief Engineer} By {R.W. Bailey - Chief Engineer} /Ald. {F. Allwood - Experimental Design} γ 606. 4 SHOE BRAKE, WRAITH FRONT AXLE. We want to try on a Wraith a four shoe brake. This means making another set of brake shoes. We are out to try to prevent brake squeaks which are a serious problem on the front of Wraith, not on the rear. We have obtained considerable evidence that the lower the pressure between lining and drum, the less likely are brake squeaks to occur. On Wraith the front shoes are narrow, the rear wide and squeak free, the Ph.III gives us little trouble on account of its massive brake and large area, the Bentley is a constant source of complaint as the brake linings are too small. Bendix of America, and the proprietary brake manufacturers of this country, and some of the friction lining makers, confirm that this is the cause of our trouble, and urge us to increase the area. R. {Sir Henry Royce} and Da. {Bernard Day - Chassis Design} were working on a four shoe brake in 1930 but it was never fitted. The Girling 4 shoe brake increases the lining area by 50% and moreover evens out the lining pressure instead of allowing it to vary by as much as 3 to 1 on different parts of the lining as it does on our brakes. The Wraith R.R. car is more suitable for operating such a brake, than the Girling expander: the resulting brake is absolutely non-wrapping. The War Office has approved the 4 shoe brake and ordered it in large quantities for Tanks, as it has six times the usual life between relinings. We are committed to Wraith brakes, they cannot be widened without increasing the track, and having new hubs, stub axles, drums, shoes and brake assembly generally. The alternative way of increasing the area consists, in effect, of using 4 tipping shoes instead of the two per drum now instructed for production, and is not likely to be more expensive than a bigger brake generally. It is also lighter. If we had had our present information about unit pressures, we would have urged the Design Dept. to widen the | ||
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).