106 Bulletin 86 



is moved forward with the mortar boxes several times a day. Large 

 sizes of pipe are lowered by means of tripod or derrick with block 

 and tackle. 



The custom in other places is to use a smaller laying crew — only 

 three or four men. The layer handles pipe up to 16 inches in diame- 

 ter alone. The addition of a few more unskilled men does not add 

 materially to the cost per day and it permits of much faster progress. 



Sixty percent of the pipe layers, it is said, do not use a laying 

 core. Over half of the pipe at Continental was laid without one. 

 Pipe layers are much divided in opinion as to the usefulness of the 

 core. Many layers make good water-tight joints, with smooth in- 

 side surfaces, without it. However, a man with limited experience 

 or who is inclined to shirk his work is much surer to place a proper 

 amount of mortar, and to secure it throughout the full circle of the 

 joint, if he uses a core, and for that reason it is recommended that 

 specifications require its use. The inside joint should always be 

 brushed even when a core is used. 



There is one pipe manufacturer in California who makes Mc- 

 Cracken bell-end pipe for irrigation pipe lines. His method of lay- 

 ing is as follows. The layer faces the bell-end of the last pipe laid, 

 and the helper straddles it. The helper washes the bell-end with 

 water and places mortar in the lower half of the bell while the layer 

 builds a fillet of mortar around a core projecting from the spigot end 

 of the upright pipe. The pipe is shoved into the bell-end, and the 

 helper fills the top of the bell with mortar. A bander finishes the 

 joint, and a mixer and a back filler complete the laying crew. No 

 excavation is made for the bells. The experience of this contractor 

 does not reveal any superiority of the bell and spigot pipe over the 

 tongue and groove pipe. 



The specifications for laying the sewer line at Glendale were as 

 follows. "Before a pipe is laid, the lower half of the hub of the pre- 

 ceding pipe shall be plastered on the inside with a stiff mortar mixed 

 1:1, and sufficient thickness to bring the inner bottoms of the abut- 

 ting pipes flush and even. After the pipe is laid, the remainder of 

 the hub shall be thoroughly filled with similar mortar and the joint 

 wiped inside and finished to a smooth bevel outside." 



A new feature introduced recently on the Thomas-Hammond 

 machine is the self-centering joint. The lower part of the bell is 

 beveled so that the spigot, when it is forced into the bell, becomes 

 accurately centered. This tends to give maximum flow capacity to 

 the pipe line. However, it was found at Glendale that the mortar 

 on the bottom interfered with the centering by raising the spigot 



