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Fluidity Experiments. A Spindle Oil. Olney Bros. Sample 16.

150

60.5

120

91.75

140

69.75

110

106.50

130

79.

100

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Fluidity Experiments.
Swift. Sample 18.

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120

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276.

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Fluidity Experiments. Champion Oil. Downer Oil Co. Sample 28.

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Fluidity Experiments. Neatsfoot Oil. Alexander Boyd & Sons.

Sample 22.

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06

Temperature.

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315.5

469.5

578.5

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DISCUSSION.

Mr. Cotter-I would like to ask the proportion of work lost by friction.

Mr. Woodbury-About twenty-five per cent. of the power was used in manipulating the fibre of the cotton, the other seventy-five per cent. was used up in friction.

Mr. Porter-I would like to inquire by what means the amount of power employed in manipulating the fibers of the material is ascertained and distinguished from the power absorbed in the various frictions.

Mr. Woodbury-That was not ascertained by me personally but by a member of this Society, in whose work I have considerable confidence, in a mill. He took diagrams from the engine and then they went to the mule-room and broke off all the roving, noting the difference of power, and then they turned off the whole power of the mule-room, and in that way went through the establishment stopping the operations. There is a second differential which I considered at the time, but knew no means of eliminating it-that the friction of the machine must be slightly greater when doing the work than when running empty.

Mr. Worthington-I think it is a matter of congratulation that so careful and capable an experimenter has taken up this subject to lubricating oil. I do not know anything in which we are so much at sea as in that, opinions differing almost as to the utility of oil at al in a steam cylinder, and I am glad to learn that he proposes to investigate cylinder oils.

Mr. Sterling-It is an important point brought out that the true test of the efficiency of oil is the dollar.

Prof. Thurston-Mr. Woodbury in his paper made some reference to the fact that the coefficients of friction, as ordinarily stated, are not found to be strictly correct; in other words that there are no such losses in ordinary practice. Then he has shown you here how seriously the temperature of the lubricant affects the co-efficient of friction. You will notice that the work done is all at extremely light pressures. It is simply due to the pull of the band, and the resultant of that and the resistance of the work of the spindle. It is exceedingly light, and it is for that reason that we get what appeared to be extremely high co-efficients of friction. In the table exhibited you will see that the co-efficients run from seven and a half per cent. up to about twenty per cent., the highest figure being lard oil, and a special grade of machinery oil, which are each about twenty-two per cent. Now, a fact which was not brought out so strongly by the paper as it might have been is, that this co-efficient is also affected very largely by the pressure per square inch put upon the journal,

and what I intended specially to remark upon was the fact that these co-efficients do not represent the values of the co-efficients obtained in ordinary engine work, but are the co-efficients obtained in extremely light work, as in the spinning frames of cotton mills. If we use the same lubricating material, and the same surface pressure rising above that to fifty pounds, we will find the co-efficients come down in value to a fraction of the figures given on the scale. Carrying the pressure up to a very common figure, such as we might get with any machine work, of one hundred or two hundred pounds, we Iwill find that the co-efficient is reduced. I have had occasion to make tests of various kinds of oil between various sorts of surfaces, and, under varying pressures and temperatures, up to pressures of fifteen hundred pounds to the square inch, and for a very short period of time two thousand pounds to the square inch, and at temperatures which ran from the ordinary atmospheric temperature to above the boiling point of water, and I find that upon the crankpins of steam engines, such as are sometimes used on the North River boats, carrying the pressure of a thousand pounds to the square inch, instead of a co-efficient of friction of five per cent., we get one-tenth of five per cent.-one-half of one per cent. for the co-efficient of friction-so that the field explored by Mr. Woodbury is limited to these extremely low temperatures. They do not represent the results as ordinarily obtained, or exceptional results obtained by putting on tremendously high pressures, so that if we take the very best of lubricating materials-sperm oil, is the best I have ever found for heavy pressures-and put a pressure upon it of a thousand pounds to the square inch, then, instead of the text-book, co-efficients of friction, all the way from four to seven per cent., we get figures that run to one-tenth of that amount. I have obtained co-efficients of friction with sperm oil as low as one-fourth of one per cent.

The pressure, therefore, at which you are working is one of the very important elements in determining what is to be the co-efficient of friction to be assumed in design.

Now, I spoke of this partly as a commentary on this paper, and partly as a commentary on that of Mr. Hoadley. Mr. Hoadley shows us that we may divide the circumference described by the crank pin by horizontal and vertical lines, and he calls the upper and lower of the two sections of his circumference, the work-doing parts of the traverse of the crank pin, and the end sections he calls the work-using sections.

Now he shows us what is the effect of friction in reducing the efficiency of engines, where we put full pressure on the crank pin at either end of the stroke; but it must be observed, as a commen

tary upon that statement, that these figures are very much smaller than we have been accustomed to assume. The friction of the crank pin in a well-made engine, with a good bronze box, running on good steel journals, ought to come down to a fraction of one per cent. That being the case, we get the result that Mr. Port r indicated, that the loss of power at the two ends of the stroke becomes insignificant, more insignificant than I presume he had supposed.

A remark was also made by another member of the Society, upon our determinations of the value of lubricating oils for steam cylin ders. In a long series of experiments, which I have had occasion to make on lubricating oils to be used in steam cylinders, I have taken oils furnished in the market for that purpose, and tested them at the temperature of the steam cylinder, bringing them up to a temperature of 250° or 300°, and some cases 350°, and I found that the value of the oil for lubricating purposes, within the steam cylin ders, is by no means the same as its value for lubricating on the crank pin, and other external parts not subjected to high temperatures, and that the oil giving the best results on the crank pin may give poor results in the cylinder.

In several cases I have found that oils that were among the best for ordinary use, were among the poorest for cylinder work; while other oils that were not nearly so good for external use, were among the very best for use within the steam cylinder. So no one can tell what is the value of an oil for the purpose to which he applies it, until he subjects it to a test under precisely those conditions. Mr. Woodbury presented us with the results of work done under the precise conditions of actual use. He runs the spindles at the ordinary speed, and runs them as in ordinary spinning frames, and then measures the friction, and the data he gives are of course absolutely reliable as determining the results to be met with under that set of conditions. That is one reason why we may rely so absolutely, I presume, upon his results. He has determined under these conditions what is the comparative value of a large number of oils; but I wish to renew his caution that we are not to take these results, which represent the relative value of oils for spindles, as representing the relative value of those oils for crank pins, or the lubrication of steam cylinders. Another remark was made in the paper, apparently incidentally, that a man may save a conside mwnt t can of money in the purchase of his oils, while losing at the vastly greater amount in paying his coal bills, and that question how are we to determine the money value of It is evident that the value to the dealer is not at all like its value to the purchaser. The money value of the oi sumer is something less than the money value of the w

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