90 Bulletin 86 



fornia, in March, 1916, and has been in successful operation since 

 that time. Another machine is in service in Yuba City, California. 



PNEUMATIC AIR TAMPERS 



Several pipe contractors, who still use the ordinary hand molds, 

 have installed air compressors in their yards, and use pneumatic 

 tampers, v^hich are similar to pneumatic hammers and drills. The 

 Ingersoll tamper, which is preferred, weighs about 20 pounds and is 

 suspended from a tripod with pulley and counterweight. It has a 

 5-inch stroke, and strikes 750 blows per minute. The head of the 

 tamper is three-fourths of an inch thick and 6 inches long, in circular 

 form to conform to the curve of the mold. The air pressure is 90 

 pounds per square inch. The compressed air is piped about the 

 yards and several pipe crews can use it at once. A 7-inch by 6-inch 

 compressor, displacing 75 cubic feet per minute, will supply two 

 crews. About 10 percent more pipe can be made than by hand 

 tamping, and the pipe is tamped more uniformly and more densely. 



THE DURYEE-COLE 



A continuous pipe machine, the Duryee-Cole, is in process of 

 manufacture and will doubtless be tried out soon. 



HAND-MADE CEMENT PIPE 



Cement pipe made and tamped by hand has become very com- 

 mon throughout southern California and Arizona. The usual style 

 of outfit is that shown in Fig. 14. It consists of outside and inside 

 collapsible forms, a rimmer for forming the tongue on the top end 

 of the pipe, enough bottom pallets for one or two days' run, hopper, 

 tampers, scoop, and shovels. Bell-ended pipe is made by hand in 

 the Middle West. An example of such pipe is shown in Fig. 2. 



After the forms are placed in position and a batch of mortar is 

 made ready, one man feeds the mortar into the forms while another 

 tamps vigorously. Care must be taken not to feed the mortar faster 

 on one side of the ring than on the other, nor faster than it can be 

 thoroughly tamped. The mortar is made of a rather dry consist- 

 ency ; most pipe makers make it unnecessarily dry. When the forms 

 are filled and the top joint (tongue) has been made, the forms are 

 carried by hand to the curing floor, where the inside form, or core, 

 is first removed from the tile and then the outside form, or jacket, 

 is removed. 



