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).
Investigation into a bell crank defect on Raphael's car, with recommendations for inspection and rectification on all cars.
| Identifier | ExFiles\Box 92\4\ scan0353 | |
| Date | 23th August 1937 | |
| -2- In view of the above we concluded that the bell crank on Raphael's car 3.AZ.60 was in some way peculiar, as it has broken two links in a short space of time. Fortunately we were able to get hold of the car and examine the bell crank. It is not correctly machined, the angular travel of the dumb bell link is restricted to 46° instead of 54° as shown on the drawings, because the countersink out has not been carried low enough and the smaller diameter is .015" too small. This has caused the neck of the dumb bell to be hit repeatedly and these impacts have worn a groove in the hard metal of the bell crank. We have examined four bell cranks on customer's cars and they show no sign of this defect; we therefore conclude only a small percentage are defective. In most cases this can be determined by external examination. The procedure is to jack the front of the car up and then take the weight of the car on its hubs with the wheels removed. This has to be done in three positions, i.e. both locks and straight ahead. The pin in the lower end of the bell cranks is then removed. If in all positions the lower end of the bell crank can be pushed outwards 1/10th. of an inch beyond the normal brakes off position then no foul is occuring. If there is any doubt about a particular car the brake drum and bell crank must be removed and the latter examined. We recommend that every car be examined in this manner and the defective ones made good. This can be done by stoning the bell crank where the foul occurs; the link must be replaced. As a further safeguard the sheetmetal stops G.83603/4 should be fixed to the pivot cap and arranged to prevent the bell crankfrom trapping the dumb bell. This should be done on every car; the cost is not great. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||