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 by E. W. Monkhouse on the performance of Perfloc nuts compared to ordinary nuts under various tests.
Identifier | ExFiles\Box 77\5\ scan0218 | |
Date | 19th April 1912 guessed | |
REPORT BY E.{Mr Elliott - Chief Engineer} W. MONKHOUSE, M.I.C.E., M.I.Mech.E. 14, OLD QUEEN STREET, WESTMINSTER, S.W. DEAR SIR, I have pleasure in giving you the following report on experiments carried out on the Perfloc nuts, and my opinion on the nut as obtained therefrom. The tests have been made to see :— (a) Whether the nut was as strong as an ordinary nut. (b) The effect of vibration on the nut. (c) Screwing-up tests, the nut being screwed up to a face with an ordinary spanner. To prove (a) two sorts of tests have been made :— (1) Tensile tests of bolts fitted with the nut. (2) Screwing-up tests, the nut being screwed up to a face with an ordinary spanner. Six tensile tests were made—two on 3/4-in. bolts and four on 1-in. bolts. One of the 3/4-in. bolts and two of the 1-in. bolts were tested as received, and the others were turned down in the shank so that the diameter of the shank was the same diameter as the bottom of the thread. At intervals during the tests the bolts were taken out of the testing machine to see whether the nut had come to any damage ; at none of the loads were the nuts found to be in any way injured, and, further, the nuts were found uninjured after the bolt had been broken. On the tests the load was applied between the under side of the heads of the bolts and the under side of the nuts. The figures obtained on the tensile tests are sent on sheets herewith. The tests show that the effect on the Perfloc nut of applying tension to a bolt fitted therewith is in no way different from the effect on an ordinary nut treated in the same way. Nuts have been hove hard up in the usual way with a spanner, and have stood the treatment as well as an ordinary nut. To prove (b), a series of tests have been made, of which the following is a description :— (1) A bolt was passed through a wooden lever in such a way that the head of the bolt could be pressed down on to a revolving spur wheel by means of a lever. The spur wheel rotated at such a speed that the bolt head, when pressed down, received 2,800 blows per minute. On to the bolt were screwed ordinary nuts and Perfloc nuts, one at a time, the two sorts of nuts being, to the feel, equally tight on the bolt. Both sorts of nuts were screwed home equally and properly. The result of the test showed that, whereas the ordinary nut was shaken loose after a few minutes' application to the vibrator, the Perfloc nut was not affected after long continued application. A test was made to see the effect on the two sorts of nuts when only screwed half-way down the thread of the bolt under the same conditions of vibration, and it was found that, whereas the ordinary nut rapidly unscrewed itself and eventually came off the end of the bolt, the Perfloc nut, on the contrary, screwed itself on and not off. (2) A 1-inch Perfloc nut was fitted to a stud on a turbo-alternator at the Generating Station of the London Electric Supply Corporation, subject to a good deal of vibration, having a rapid periodicity owing to electrical causes. In this case the ordinary nuts originally fitted to the studs were found slack after a few hours' running, so that it became necessary to washer up the nuts in such a way that when hardened up they were in close contact with a split-pin passed through the stud at the back of them. The Perfloc nut was fitted, on February 21st, to one of these studs without special washering, and leaving 1/8 inch space between the nut and split-pin, giving ample room for starting back. On the 1st April the nut was examined, and was found well up to its work, not having slacked back at all. Between February 21st and April 1st the nut was not touched. (3) Three 3/4-in. Perfloc nuts, without any lock nut or guard pin, were fitted to studs holding down the guard plate on a large boiler feed pump at the Generating Station of the London Electric Supply Corporation. It had been found necessary for ordinary nuts placed in this position to be securely locked, as otherwise they invariably slacked out. The three nuts referred to were fitted on March 12th, and the pump ran until March 26th, having worked 270 hours in the interval. On March 26th the pump was opened out, and the nuts were found perfectly tight. (4) Nuts were fitted to the bearings of two counter-shafts on pumping machinery at the Rickmansworth and West Drayton Pumping Stations of the Rickmansworth and Uxbridge Valley Water Company. The countershafts are direct connected to gas engines, and drive spur wheels through pinions fitted to their ends. The shafts are subjected to a great amount of vibration, and the nuts on the bearing caps have always given a deal of trouble, and have constantly required tightening up. Perfloc nuts were fitted to these bearings, and remained perfectly tight for six weeks, at the end of which time the plants were shut down for repair. All the nuts were marked, and some were sealed up. The shape of the spring thread in the Perfloc nuts is such as to fill the thread on the bolt and the female thread in the nut at least as well as the thread on commercial bright bolts are filled by the thread on their nuts, so I consider that the Perfloc nut should not be any more liable to damage through rusting action than is ordinarily the case. The nuts submitted and tested were to Whitworth standard, and were used on standard Whitworth studs and bolts. I consider the nut to be a practical commercial article. Faithfully yours, (Signed) E.{Mr Elliott - Chief Engineer} W. MONKHOUSE, M.I.C.E., M.I.Mech.E. | ||