“The Best Methods of Using Thin Oils.—This will show us that oils which are deficient in body, but which are good in other respects, may be used with good results if doled out in small quantities, as required, by automatic oil-cups like the Lieuvain needle lubricator, [Fig. 2498], or any other means. Journals which cannot be fed by means of automatic oil-cups in positions difficult of access should be fed with oil which has a good body. If time permitted, much might be said of the proper shape for bearings of machinery—a subject which would lead to valuable results if discussed by the members of this Society, many of whom must have great experience of those designs which have produced the best results, as well as of those mixtures of metals which are the most durable for light high speed and heavy slow shafting. If any member will take up this subject, or if several members will read short notes, giving their actual experience of different sorts of footsteps, pedestals, and spindles, as well as of the use of different sorts of oil-cups and lubricators, it will be highly advantageous knowledge, which must be of great value to all who use machinery.
Fig. 2499.
“Fluidity of Oils.—Continuing my remarks on the thinness or fluidity of oils, I wish to call attention to an ingenious arrangement for testing the fluidity when subject to a slight increase of temperature, and also for detecting any tendency which they may have for combining with the oxygen of the atmosphere; this latter quality being advantageous in oils which are used to mix with paint, but which is a great evil when used for lubricating purposes. A piece of plate-glass placed at an angle is made warm to 200° Fahr. A drop of oil when placed on the upper end of this glass will flow down a few inches and thus indicate its fluidity when subjected to increase of temperature. [Fig. 2499] shows a ready method I have designed for testing oil in this way. It consists of a tin box in which is fixed the glass, through which can be seen a thermometer. A graduated scale at the side of the box enables the track of the oil to be measured. The box has a door at the back which enables a copper vessel full of boiling water to be introduced; the box is lined with felt to prevent rapid radiation, and when the door is closed it will be seen that several experiments may be conducted before the apparatus becomes too cool for use. I think this a cleaner way than using a lamp for the purpose. The copper may also be used by itself for indicating the behavior of oil on copper when slightly warm in making it discolored or otherwise. As I have before stated, there are many oils which are good lubricants, but which become too thin when exposed to slight heat, and I do not hesitate to reiterate the statement, as I wish to have some influence on the future designs of bearing in this district. A correspondent writing to Engineer from Queensland says that for six months in the year oil runs off the machinery like water and seems to have no lubricating power; he says that the thermometer registers in the summer 140° in the sun, and 110° in the shade. Great difficulty seems to have been experienced by him in keeping oil on the bearings; his experiments on locomotives show that it costs for lubricating a locomotive there about a halfpenny to three farthings a mile, according to the mixture used.
“Influence of the Atmosphere on Oils.—There are some oils which are excellent lubricants for the first few hours of use, but which have a low capacity for resisting the influence of the oxygen of the atmosphere upon them. The warm glass test may be used for indicating this weakness. If after the test for fluidity the oil be permitted to remain on the glass any exhibition of a resinous or varnish quality may be observed. Another test for this resinous or gummy quality is one which has been suggested to me by Mr. F. R. Wheeldon, of Bilston. He has made many experiments. He found that by permitting oil to remain on a Stapfer friction tester after one test which had been recorded, he tested again on the following day, without adding any fresh oil. This is a severe test, as the thermometer was made to indicate 200° Fahr. each time.
Fig. 2500.
“Longevity of Lubricants.—Supposing an oil to possess all the qualities which we think a good lubricant should have—that it has fluidity in season, and that it does not combine with the atmosphere and become varnish, that it does not become like water in summer and like mutton suet in winter, and is in most respects satisfactory. We then want to know its powers of endurance, its capacity to resist wear and tear—in other words, its longevity. A good test for longevity or durability of oil when subject to either heavy or light frictional pressure is one suggested by Mr. W. H. Hatcher, a very careful investigator, and chief of the Laboratory of Price’s Patent Candle Company, who are extensive oil manufacturers. It consists in taking away the bottom step of the Stapfer tester and placing a small dish containing oil underneath the friction roller (as in [Fig. 2500]). This oil is carefully weighed before and after several hours’ frictional wear and tear. The drawing ([Fig. 2501]) shows the application of this mode, which I have designed, for testing solid lubricants, such as lard and sulphur and other railway and steamship mixtures. It will be seen that the material is kept to its duty by the weighted lever, and its progress of diminution can be tested in its place by the scale-beam arrangement. When it is used with the pressure on the top step it is advisable to drive it at about 2,000 revolutions per minute; otherwise much time will be occupied in destroying a weighable quantity of oil. The large Stapfer tester ([Fig. 2502]) was designed a few months ago for this purpose for the Government railways of New South Wales, and it is also used by the Manchester, Sheffield, and Lincolnshire, the Lancashire and Yorkshire, and other railways. I have not been able to get any results of these tests in time for our subject on this occasion, but hope to do so at some future time. The frictional roller is 6 inches in diameter, the pressure amounts to 1 cwt. on each step. As it takes a considerable time to wear away half a pound of solid lubricant, it may be advisable to measure by minutes instead of using the speed index. The speed should be at least 1,500 revolutions per minute. The Stapfer tester should be used in a room of equal temperature, and should not be subject to draughts of cold air, as it will be obvious these will interfere with the indications of the thermometer. A recent alteration in the Stapfer tester permits the quantity of oil used for testing to be measured with greater accuracy than before. A small oil-hole is made in the top step (see [Fig. 2502] at a and at c) in which is placed a glass tube. This only holds a few drops, and can be filled by simply dropping the oil in, holding the finger at the bottom to prevent it running away, and then place it in the hole. If a small needle lubricator be weighed and then filled with oil of a definite weight, and placed in this hole (see [Fig. 2502] at b), oil may be tested for longevity and for its anti-frictional properties for a longer period than with the small tube. If oil be placed in this at the same time that oil is placed in the lubricators in the works and the oil tester be driven from the same shafting, permitting it to stop and start when the engine stops and starts, the effect of a week’s work upon the weight of the oil may be seen; notice should be taken of the difference of the temperature between the thermometer on the instrument and the temperature of the atmosphere of the workshop.