128 PRACTICAL INSTRUCTIONS REGARDING THE USE OF 



We have already shown that a double-effect drum does the 

 work per acre at less cost than a single-effect drum, the only 

 troublesome point in the former being the anchoring of the 

 fixed pulley. The steel anchors with two spikes give the 

 best results, but they require to be strongly fixed, and many 

 persons do not know how to manage them. We must not 

 hesitate to place two or three behind each other joined 

 by chains, if necessary. Moreover, if it rains during the 

 night they must be pulled out and refixed. The anchors are 

 completely sunk in the ground, and each of the spikes must 

 be stayed by cross pegs t t (Fig. 82) ; the direction of the 

 anchor must be carefully ascertained, as its position has great 

 importance on their fixity. This is arrived at by an invariable 

 rule ; the line m n passing by the point of application of the 

 pulley, must form equal angles a oc , with the two parts of 

 the cable passing over the pulley. The workmen find it by 

 the following simple and practical method : A rod 8 feet 

 in length is taken, and one end placed in i, the point of 

 intersection of the two parts of the cable ; the distance the 

 rod reaches in each direction is marked off, the two points 

 joined by a rope and the point of the centre o determined. 

 The direction o i is the direction sought. This method 

 applies to any system of anchoring, for, when beams are 

 used, they must be placed perpendicular to that line. 



The fixed pulleys should be of large diameter, and fixed 

 on wide plates. Fig. 82 represents a strong type of suitable 

 dimensions. The pulley P is 33J inches in diameter, and 

 has a groove 2^ inches deep ; it is thicker near the pivot, 

 which is slightly conical, and has an average diameter of 

 2-fo inches. This pivot A traverses an iron plate q r 

 slightly countersunk and inclined towards q and an oak plate 

 19^ inches wide, 3ft. 3in. long, 3 inches thick, strengthened 

 on the side by two iron plates f jf, bolted through at p p . 

 The pivot A is held by a nut #, taking in at the same 

 time a flat iron piece 2^ inches in width, c c'. 



This piece c c' is bent and rounded at c to a distance level 

 with the top of the pivot ; a piece d terminated by a hook 

 fits on it ; a pin keeps the piece d on the pivot A, another 

 <f on the piece c ' . This piece is indispensable to prevent the 

 pivot A from bending under the traction of the cable. 



The piece d may revolve round the pivot A to allow the 

 cable to be taken out of the sheave. At the rear, a V-shaped 



