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).
Letter to The Gates Rubber Co. discussing issues with British-made belts and requesting suitable American belts for testing.
| Identifier | ExFiles\Box 135\1\ scan0127 | |
| Date | 15th February 1938 | |
| Messrs. The Gates Rubber Co. -2- 15th. February 1938. We think it best to explain here that there is no question of our using American belts in production on our cars since we have a ruling that only products available in this country may be fitted to them. Our tests so far with this British made American type belt indicate that it is very much superior to any belt previously tested - our only trouble has been with the biggest size belt to EXS.194 transmitting the large power mentioned above. With this belt we have had three cases of the belt turning inside out on the pulleys. Sectioning and examination of the belt has shown that the cords have pulled loose in the rubber surrounding causing the section to distort. As previously mentioned the horsepower transmitted is approximately 16-20 while the pulley diameters, both driving and driven are 3.450". The pulley speed (driving) is 4250-4500 r.p.m. We would be interested to hear whether you have had any similar experience and whether you can advise us as to the best way of altering the belt to get over this difficulty. Also we would like to know whether in your opinion we are asking too much in trying to get a belt of the general dimensions shown on EXS.194 to transmit 16-20 H.P. continuously under the above mentioned conditions. The maximum belt life under endurance conditions which we have had so far is 8 hours at 4250-4500 driving pulley r.p.m. with the American type construction belt made in this country - our old type belts only last 2-2 1/2 hours under these conditions. Further, the new belt gives an apparent slip of approximately 5% (measured by speed of fan compared with speed of engine) while the old type belt gives slip figures of 12-20% and stretches very badly. We are anxious to get some comparative figures with American belts, in particular your Concave Walled type. The pulley sheave groove angles which we are using are 24° (driving and driven) with a top width of sheave groove of .900 for the EXS.194 belt and 28° (driving and driven) with a top width of sheave groove of .675 for the EB.221 belt. However, with the EB.221 belt the driven pulley is 5.675" exterior diameter, while the driving pulley is 5.151" dia. for these pulleys if you make same - if not, the nearest sizes you have would do and we will make pulleys to fit them, if you will give us the correct Vee angles and widths for same. Two belts of the large size and three of the samll size would be quite adequate for our tests. | ||