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).
Report to Messrs. Ferodo Ltd. on the testing and peculiar behaviour of fan belts.
| Identifier | ExFiles\Box 135\1\ scan0104 | |
| Date | 21th December 1937 | |
| Messrs. Ferodo Ltd. -2- 21.12.37. In view of this we should require these belts approximately 3/4" - 1" longer - we will let you know the exact figure later. We would like to know whether the mould can be altered to give this length, and if so would like you to make this alteration, at our expense of course, and supply us with a further three belts from it for test purposes. In connection with the question of initial belt tightness and over-stress, we had a peculiar experience with one of your new belts. As tried initially with fan pulleys giving a fan speed/engine speed ratio of 1/1, the belt was seen to be far too tight, it was therefore run with a smaller driving pulley (giving a ratio of .9/1) which dropped the belt tension to a more reasonable amount. The belt was run for 1 hour under maximum load and speed conditions and the tension dropped very slightly. The higher ratio driving pulley was then refitted and the belt was still very tight. Further, by an oversight it was put on incorrectly, i.e. it was placed on the driven pulley and forced over the driving pulley by turning the engine on the starter. In spite of this unduly high initial tension, the belt was then run in the hope that it would slacken. However, after two minutes running the belt came off and was found to have turned inside out. It was refitted and it was observed that the section of the belt in the pulley Vee was as shown on attached sketch. After a further five minutes running, the belt again turned inside out although in this case it did not come off its pulleys. Examination of the belt section showed it to be distorted. We are returning the belt to you to-day for your inspection. The pulley centres were then altered to reduce the initial tension and a new belt was fitted. As mentioned above no trouble whatever has been experienced with the belt during two hours running. We would like to hear from you as to any theories which you can suggest to account for the peculiar behaviour of the first belt. The only one which occurs to the writer is that the initial forcing of the belt over the driving pulley distorted it and caused it to run down one side of the pulley Vee and up the other. In any case this occurrence emphasises the need for care in initial fitting of these belts. | ||