Filing, polishing, a cleaning out of the oil hole or oiler, and the taking of proper precaution against future failure of lubrication will put everything into first-class order. When the loose pulley is, as it is best for it to be, farthest away from the bearing, held in its place by the tight pulley and a collar, not only is the tight pulley better adapted for carrying its load, owing to additional support resultant from its proximity to the bearing, but such matters of small repair as come up are much simplified.
Fig. 28 in some degree, aside from the cutting up and heating of the bearings, illustrates the breaking strain, in addition to the usual torsional strain, which becomes enhanced in direct proportion with the increase of breaking strain, to which an out-of-line or out-of-level shaft is subject. The bends are exaggerated for illustration.
In this instance, the fact of one hanger-bearing being out of line or level subjects the shaft to a severe breaking strain. The shaft being both out of line and level does not, if both at the same point, aggravate matters, as might at first be supposed.
It is true that the full torsional strength of a shaft is only equal to the weakest portion of it, so that three weak spots more or less can, theoretically, make no difference one way or the other. But, practically, there is the undue strain and wear of the bearings at these points, and if a pulley transmitting any considerable amount of power is situated anywhere along the length _A B_ it is sure to be unpleasantly in evidence at all times.
Only an eighth or a quarter out, but oh, what shaft-breaking stories that fraction could tell!
The following is a simple method for testing the alinement and level of a line of shafting that is already up.
As in Fig. 29, stretch a line _C_ so that it is exactly opposite the shafting. Set it equidistant from the shaft end centers _G_ and _F_ and free from all contact along its entire length except at its retaining ends _A_ and _B_. Now, it is self-evident, as line _C_ is straight and set equidistant from the shaft end centers _G_ and _F_, that if you set the entire center line of the shafting at the same distance from line _C_, as _G_ and _F_, you are bound to get your shafting into perfect alinement.