Fig. 38.
Generally the necessary supporting beams will not all be found within the shaft's length distance C D; in such cases continue your cutting in the same parallel line to A B, as at E or F, going from C D outwardly until you strike the sought-for beams. Having located beams, say 1 and 2, we find by measurement that they are 5 feet apart, and, as beams are generally uniformly spaced, we may start 4 feet 6 inches (go 4 feet 6 inches and not 5 feet, to make sure not to skip beam 3 and thus make a cut that will not be covered by the stringers) from 1 to cut outwardly for the location of beam 3.
Where the building's beams run parallel to the shaft, Fig. 39, mark the counter's-center line A B, and then mark the spaces—as determined by the countershaft length, floor position of the driven machine or the driving point on the main shaft—to be occupied by the stringers C D, and, starting from the center line A B, cut outwardly each way to the desired beams 1 and 2.
Fig. 39.
Where the center line as laid out (before the position of the ceiling beams was known) brings it close to or directly under a supporting beam, it is generally advisable where possible to step the counter back or forward to a central position between the beams.
Where shafting is already in place in a building, no matter on what floor, valuable measurements as to beam location can thus be had from the plainly in sight and the reasonably deducible. Lacking in-place-shafting to go by, the walls, columns and main girders always clearly indicate the crosswise or parallel run of the ceiling beams to the proposed shafting line.
In the usual method of locating the timbers of a boarded-over ceiling, a brace and bit, or a nail, can be used for the purpose. If shy of an awl, and in preference the other two ways, force or drive a chisel (cold chisel or wood) in between a tongue and groove of the ceiling boards in stringer space (Fig. 38) E or F, and thus spring the boards sufficiently apart to insert a compass saw. With the extremity of a 12-inch saw a very little cutting (along the tongue and groove, as this shows least) will enable you to locate a beam, since they generally run 8, 12, 16, 20, 24 and 30 inches apart.
Always, on locating your beam, run the point of your compass saw down the whole of the timber's width, so that any nailed-on pieces will not lead you into a false estimate of the beam's thickness.