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).
Propeller shaft vibrations and mechanic joint issues on an S.S. car.
| Identifier | ExFiles\Box 11\2\ 02-page086 | |
| Date | 27th January 1929 | |
| X794b 85 To: Hs.{Lord Ernest Hives - Chair} From: G.W.H. Hôtel de France, Châteauroux, Indre. January 27th. 1929. We had a run out on the S.S. car this morning. We should not consider that the torque reaction is any worse after fitting a new engine fabric coupling. We have run into serious trouble with the mechanic joints on the propeller shaft. A very bad period developed up at 45 M.P.H. and upon returning to the Garage we found that all the oil had been flung out of the front joint. Before proceeding with the whys and wherefores, we have noticed throughout the test a period at approx. 45 M.P.H. and have attributed it to an engine period. This is definitely not so, so that if you notice this period on any of your S.S. cars it comes from the propeller shaft. If you observe the shaft at this period you will see that it vibrates considerably. The front mechanic joint, which has given the trouble, was taken down for examination and we find that it can be badly distorted by over-tightening the nuts. We also observed that the freedom of the bearings is affected by this distortion. It would appear that the machining of the bearing spigots and the covers have to be made with no limits whatsoever. The spigot faces have also to be accurate to .001" or else it is impossible to tighten the nuts up without cross binding the bearings. Another feature is that upon tightening the nuts the spigot bearings can follow round in the direction of the nuts, thus causing a binding effect that way. It would appear that a definite length of spanner is needed so that over-tightening could not occur to overcome any tendency to distort the covers. We should like you to make discreet enquiries from the fitters who assembled these mechanic joints. The reason is that we found 2 nuts only finger-tight although they were locked up by the locking plates. The reason was obvious, for as soon as we put a spanner on them the coupling could not be moved. We even find that if one half of the covers is taken off, considerably more freedom is given to the universal action. This means that the holes in the covers are slightly out of line for the spigots and when the cover is fitted it places the strain on the spigot bearings, causing them to bind. The covers in our opinion are too weak for the job and, as we have stated, absolutely accurate machining with no limits whatsoever will have to be attained. We have carried out to-day a test for RM{William Robotham - Chief Engineer}'s information: With 2 gallons of petrol in the rear tank it took 4 min. 54 2/5 seconds to suck one pint of petrol, with the starter motor turning the engine over at the rate of 68 revs. per min. With 1 gallon of petrol in the rear tank we could get no suction. There elapses approximately 20 seconds between each period of delivery. G.W.H. | ||