This is not all the fault of the engineer or the belt manufacturer. Often belts are made uneven, and soon get out of shape, even with the best of care. We sometimes find a belt that ordinarily runs easy on the pulleys and does its work with ease suddenly inclined to run to either one side or the other of the driven pulley. This is caused by one of two things—either the belt has been too slack, or the load increased for want of lubrication, or other causes. In either case it will run off if you insist on applying the power. The remedy would be to take up the belt, thoroughly oil the journals, or take off the extra load—maybe a combination of all. Still a little extra work making the belt tighter will enable it to run well and do the extra work just as long as the extra tension can be maintained. Then it may appear perplexing and run to one side of the driven pulley when the driven shaft gets out of line with the driving shaft. In a case of this kind the belt does not run to what is called the high side of the pulley, but to the low side. Another peculiar indication: If two shafts are parallel and there is a high place on the pulley, then a belt will run to the high place; but if the shafts are out of line, or, in other words, are not parallel, and the face of the pulley straight, then the belt will run to the low side or that closest to the driving shaft. The remedy would be to line up your shafting.
The object of this chapter is not to say how belts are made, but to impress upon the minds of belt users that to get the best results, belts, like all good servants, must be well cared for, and all responsibility should rest with one man, just as with your engine or any high-priced machine.
XI
A COMPARATIVE TEST OF FOUR BELT
DRESSINGS[8]
During January, 1905, a comparative test of the working efficiency of four belt dressings and preservatives was made by T. Farmer, Jr., and the writer. The test was made on the regular belt-testing machine of Sibley College, Cornell University, a full description of which appeared on pages 705-707 of Vol. 12, Trans. A. S. M. E. This machine tests the belt under actual running conditions, though our belts were in somewhat better than average condition. The four belts were new 4-inch Alexander No. 1 oak-tanned single-ply, and were 30 feet long. Particular care was taken to keep them free from oil and dirt. The belts were first tested as received from the manufacturer, after which each belt was treated with one of the dressings and again tested.
[8] Contributed to Power by William Evans.
The dressings were two semi-solids, designated No. 1 and No. 2; a bar, No. 3, and neatsfoot oil, No. 4. As the first three are proprietary articles, it was not thought best to give their names, though any one familiar with the actions of belt dressings will readily recognize No. 1 from its peculiar curve. In applying the dressings, we followed directions carefully, and in the case of Nos. 2 and 3 exceeded them. The belt was given a five-hour run, during which two or three applications of the dressing were given, and then it was set aside in a warm place to allow it to absorb the applied dressing. After thus "soaking" for at least forty-eight hours, the belt was again run, this time for three hours, with one more application of the dressing. As No. 3 was a bar of sticky dressing, it will readily be seen that this precaution was not really necessary. No. 4, the neatsfoot oil, was not applied during the last run, as we were afraid of getting too much oil in the belt. As this oil is so extensively used by engineers for dressing belts, special care was taken to get the best possible results with it.
