When the reboring method cannot be used—as when the hangers are carried by lag screws, lag-bolts, bolts screwed directly into supporting iron girders, etc.—it is evident that hanger adjustment can be secured by packing down one foot of the hanger base, as shown in Fig. 37.
Fig. 37.
The piece of packing (necessarily wedge-shaped) between the hanger foot B and the stringer A tilts the bottom of the hanger forward. The size of the wedge regulates the amount of adjustment. Wedge-shaped space D, at foot C, should also be packed out so as to avoid throwing undue strain upon C's extremity c. If now, the foot c of the countershaft's other supporting hanger (No. 2) be similarly and equally packed, as B of No. 1 hanger, the shaft will have been thrown forward at one end and back at the other, and thus into line. The equal division of the adjusting wedge packing between the opposite feet of the two hangers enables a limited packing to do considerable adjusting without any undue marring effect; and, further, insures the shaft's remaining level, which evidently would not be the case if only one hanger were packed down.
After so adjusting, be sure to get your hangers squarely crosswise of the shaft as readjusted, so that the hanger bearings will lie in a true line with the shaft and not bind it. At all times be sure to have your hangers hang or stand plumb up and down; as, if the bearings are not so pivoted as to be horizontally self-adjusting, excessive friction will be the lot of one end of the bearing with not even contact for the rest of it. The bearing being self-adjusting all ways, square crossing of the shaft line by the hanger line and plumb still remain eminently desirable for appearance's sake.
Before a countershaft can be put up on a ceiling whose supporting timbers are boarded over, or in a modern fireproof structure whose girders and beams are so bricked and plastered in as not to show, it is necessary to positively locate those of them which are to carry the stringers.
It is in the earnest endeavor to properly locate these that the unaccustomed hand turns a wood ceiling into a sieve and a brick one into a wreck. To avoid kitchen and house razing effects, try the following recipe:
We will assume that line A B, Fig. 38, laid out by one of the methods previously described, is the center line of the proposed countershaft. The hanger's base length, lateral adjustment and individual foot length call for stringers 4¾ inches wide, placed 5¼ inches apart or 14¾ inches outside (as per sketch). The floor position of the machine to be driven, or the driving point of the main shaft, is so located with reference to the countershaft that one of the supporting hangers must go at or very near C, and the countershaft's length brings the other hanger at or very near D.
Now between points C D and with due reference to the center line A B, lay out the position which your stringers are to occupy. It is self-evident that by confining your beam prospecting to the stringer spaces E and F, ultimately, when the countershaft is in place, all the cut-up portions of the ceiling will be hidden from view.
