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).
Reports and description of Perfloc lock-nuts, including vibration and corrosion tests.
Identifier | ExFiles\Box 77\5\ scan0216 | |
Date | 25th August 1914 guessed | |
REPORT BY MESSRS. WM. ROBERTSON & SONS. 121, ST.{Capt. P. R. Strong} VINCENT STREET, GLASGOW. GENTLEMEN, We beg to report as follows on the Perfloc nut, which has been put to a practical test under our observation at the Allan-shaw Coal Company's Pits, Hamilton, Lanarkshire. The nut was tested on the following machinery :โ (a) On two piston packing glands of the winding engine. (b) The engine driving the cleaning plant. (c) The underground pumping plant. In reference to (a). The nuts were first placed in position on December 22nd, 1911, and remained on for a month without showing any signs of loosening or wear. They were then removed and replaced on January 30th, 1912; we examined them on the 7th of February, and again on the 12th of the same month, and found them thoroughly satisfactory. The nuts were subjected to considerable vibration in this position, which was increased by the fact that the engine is by no means modern, and also in addition to this they were under the extra disadvantage of great strain caused by the continual reversing of the engine. In reference to (b). The nuts here were subject to greater vibration and rough usage, but came through the test with equal satisfaction. The vibration under test (b) was more constant than under test (a). The nuts were on the engine for 52 days. In reference to (c) we can only report what we have said as regards tests (a) and (b), and the nuts fulfilled their purpose thoroughly on this important piece of mining machinery. In all cases one of the nuts took the place of two ordinary nuts. Of the nuts tested by us all gave us entire satisfaction. We were considerably impressed by the effective way in which the releasing spring acts, and however tightly the nut grips the bolt we found by pressing the projecting arm back the nut was easily disengaged with the use of a spanner. Being self-contained, no grit or dirt can enter and interfere with the spring, even in any dry and dusty sections of a mine in which it may be exposed. We have also to note that the nut is of standard size and takes up no more space than an ordinary nut, and is the best lock-nut that has come under our notice. We beg to report to you that from the tests, which were severe, we have made we are perfectly satisfied that the nut grips the bolt tightly and does not work loose. We are, yours faithfully, (Signed) WM. ROBERTSON & SONS. REPORT BY MR. R.{Sir Henry Royce} RANKINE LYNN, 144, ST.{Capt. P. R. Strong} VINCENT STREET, GLASGOW. DEAR SIRS, LOCK NUTS. I have made a number of tests as instructed upon the above, particularly from the point of view of corrosion. I have suspended a steel nut on a piece of your phosphor bronze wire in the following liquids :โ 1. Paisley town water (excellent quality). 2. Corrosive river water. 3. 1 per cent. nitric acid. 4. 2 per cent. sulphuric acid. 5. 1 per cent. hydrochloric acid. Naturally steel corroded under such conditions, but the phosphor bronze wire did not corrode nor did it go into solution. I send you under separate cover steel bolt with steel nut and Phosphor Bronze Wire attachment. I placed the nut in position on the bolt and immersed the whole in 3 per cent. sulphuric acid for six days of twenty-four hours each. The acid was renewed every day. You will notice that whilst the steel exposed to the acid is heavily corroded the Phosphor Bronze Wire is as bright as when it was made. Further, the position of the thread on the bolt covered by the nut is perfectly bright and clean, showing that the acid had not entered the thread, and proving, I think, a very good fit by your system. Yours truly, (Signed) R.{Sir Henry Royce} RANKINE LYNN. PERFLOC NUTS. That there is a great demand for an efficient lock-nut is only too obvious from the number of cumbersome and expensive locking devices that have from time to time been placed on the market. The Perfloc nut, which is of standard size and can be used on any bolt, combines the functions of a nut and locking device. The outstanding feature of the nut is that the greater the vibration, the tighter it becomes. It has been shown, when an ordinary nut and a Perfloc nut were screwed half way down the thread of a bolt, that whereas the ordinary nut rapidly unscrewed itself, the new nut screwed itself on and not off. Such nuts, although subjected to considerable vibration and to great strain, have remained in position without showing any signs of loosening or wear, whereas ordinary nuts previously used in the same positions required constant tightening up. The Perfloc nut is direct in action, locking itself instantaneously and automatically. It will be seen from the accompanying photograph that the thread consists of a spiral spring. This is anchored at one end into the top of the nut, whilst the other end projects slightly beyond one of the faces of the nut, a slot being cut on the nut to take this end without jamming on the face of the washer. | ||