Fig. 2592.
For horizontal adjustment, all we have to do is to place a straight-edge along the planed face of the target, and adjust the shaft equidistant from the straight-edge, as shown in [Fig. 2592], in which a is the shaft, b the target, c the straight-edge referred to, and d a gauge or distance piece. If, then, we apply the straight-edge and wood gauge to every target, and to the adjustment, the whole line of shafting will be complete.
There are several points, however, during the latter part of the process at which consideration is required. Thus, after the horizontal line, marked on the targets by the straight-edge and used for the vertical adjustment, has been struck on all the targets, the distance from the centre of the shafting to that line should be measured at each end of the shafting, and if it is found to be equal, we may proceed with the adjustment; but if, on the other hand, it is not found to be equal, we must determine whether it will be well to lift one end of the shaft and lower the other, or make the whole adjustment at one end by lifting or lowering it, as the case may be. In coming to this determination we must bear in mind what effect it will have on the various belts, in making them too long or too short; and when a decision is reached, we must mark the line c, in [Fig. 2590], on the gauge accordingly, and not at the distance represented in our example by the 15 inches.
The method of adjustment thus pursued possesses the advantage that it shows how much the whole line of shafting is out of true before any adjustment is made, and that without entailing any great trouble in ascertaining it; so that, in making the adjustment, the operator acts intelligently and does not commence at one end utterly ignorant of where the adjustment is going to lead him to when he arrives at the other.
Then, again, it is a very correct method, nor does it make any difference if the shafting has sections of different diameters or not, for in that case we have but to measure the diameter of the shafting, and mark the adjusting line, represented in our example by c, in [Fig. 2590], accordingly, and when the adjustment is complete, the centre line of the whole length of the line of shafting will be true and level. This is not necessarily the case, if the diameter of the shafting varies and a spirit-level is used directly upon the shafting itself.
In further explanation, however, it may be well to illustrate the method of applying the gauge shown in [Fig. 2590], and the straight-edge c and gauge d shown in [Fig. 2592], in cases where there are in the same line sections of shaftings of different diameters. Suppose, then, that the line of shafting in our example has a mid-section of 21⁄4 inches diameter, and is 2 inches at one, and 21⁄2 inches in diameter at the other end: all we have to do is to mark on the gauge, shown in [Fig. 2590], two extra lines, denoted in figure by d and f. If the line c was at the proper distance from a for the section of 21⁄4 inches in diameter, then the line d will be at the proper distance for the section of 2 inches, and e at the proper distance for the section of 21⁄2 inches in diameter; the distance between c and d, and also between c and f, being 1⁄8 inch, in other words, half the amount of the difference in diameters.
In like manner for the horizontal adjustment, the gauge piece shown at d in [Fig. 2592] would require when measuring the 21⁄4 inch section to be 1⁄8 inch shorter than for the 2 inch section, while for the 21⁄2 inch section would require to be 1⁄8 inch shorter than that used for the 21⁄4 inch section, the difference again being one-half the amount of the variation in the respective diameters. Thus the whole process is simple, easy of accomplishment, and very accurate.
If the line of shafting is suspended from the joists of a ceiling instead of from uprights, the method of procedure is the same, the forms of the targets being varied to suit the conditions. The process only requires that the faced edges of the targets shall all stand plumb and true with the stretched line. It will be noted that it is of no consequence how long the stretched line is, since its sag does not in any manner disturb the correct adjustment, but in cases where it is a very long one it may be necessary to place pins that will prevent it from swaying by reason of air currents or from jarring.
The same system may be employed for setting the shafting hangers, the bores of the boxes being used instead of the shafting itself.