84 Bulletin 86 



The rate of output claimed for the National machine is 700 feet 

 of 14-inch tile per day, 600 feet of 18-inch, 550 feet of 24-inch, and 

 350 feet of 30-inch. Eight men are needed for sizes up to the 20- 

 inch and eleven men for larger sizes. The wall thicknesses of the 

 pipe are the same or a little greater than those given in Table I. 

 The mortar is mixed drier than for the McCracken, as otherwise the 

 tampers work through it instead of on it. 



One form of made-up reinforcement that has been used with the 

 National machine consists of two rings of heavy wire, one close to 

 the inside of the pipe and the other near the outside, the two rings 

 being connected at intervals by wire spacers, all electrically welded. 

 It is called double hoop reinforcement. 



THE MONARCH 



The manufacturers of the National also make the Monarch, 

 which ia similar in principle to the McCracken and Schenk machines. 

 It has a solid heavy cast frame, surmounted at the top by a sort of 

 walking beam which raises and lowers the packer shaft. The beam 

 is attached to the shaft through a ball thrust bearing. The Monarch 

 is designed for making drain tile from 5 to 20 inches in diameter. 

 The table on which the smaller sizes are made has six stands for 

 the jackets, so that the operation of the machine is very rapid. Two 

 lengths of tile can be made, 12 and 18 inches. 



THE THOMAS-HAMMOND 



All of the preceding machines except the Sherman are made in 

 Iowa. Another machine, the Thomas-Hammond, originated in Ta- 

 coma, Washington, in 1908. The product of the Thomas-Hammond 

 machines is called "glazed cement pipe," and is accepted by leading 

 cities on the Pacific coast for sanitary sewers. 



Several changes have been made in the original design of the 

 machine so that it is now much more compact, accessible, and port- 

 able. The newest model is now called the Hammond, and about a 

 score of them are now in service. This machine uses the tamping 

 principle, but, while the outside form and tile revolve under the 

 tamper, the inside form stands still and serves to give the tile a 

 smooth or glazed interior surface. The concrete is fed into the 

 mold in a uniform stream and in layers about 1^ inches deep. The 

 tamper strikes 400 blows per minute, each blow being from 300 to 

 500 pounds, depending on size of pipe. The revolving table is so 

 timed that the blows overlap. The tamper is of oak or hickory and 

 rises automatically, due to the compacting of the concrete. When 



