Manufacture of Cement Pipe 99 



To change the machine from one size of tile to another requires 

 about an hour's time. This is done sometimes during the noon hour 

 or after working hours in the afternoon. 



The advantage derived from reinforcing machine-made pipe is 

 not fully determined, but it seems probable that much reinforced 

 pipe will be used in the future with the extension of the field for 

 cement ])ipe. For machines of the National type, double hoop rein- 

 forcement is the best. For packer-head pipe machines some form 

 of cage in which the circular rings are supported is preferable. At 

 Continental electro-welded hoops of No. 7 wire were tried first. The 

 rings were of a size to fit into the corrugations of the jacket, where 

 they were securely held. Three rings per 2-foot pipe were used, 

 and they were found to be firmly imbedded in the concrete. But 

 there was difficulty in getting the rings properly welded in local 

 machine shops, and on account of the surface position of the rings 

 they could not be expected to resist corrosion. Cages made of hog 

 wire were next tried with success, and later similar cages made of 

 "Triangle Mesh." The last proved to be the best adapted to the pur- 

 pose ; it is rigid and stays in position in the jacket. The mesh comes 

 in rolls of 150 feet, and in various widths, of which the 20-inch width 

 was selected. The longitudinal wires in the mesh are 4 inches apart 

 and are thoroughly braced by the cross wires which run diagonally. 

 When the reinforced pipe were tested in the internal-pressure 

 machine, the results were disappointing. There was no increase in 

 strength, and there was some leakage along the lines of the wires. 

 This same type of reinforcement was tried in a tamping machine in 

 California, and it was found that the steel weakened the pipe 

 greatly. A correspondent who uses double-hoop reinforcement 

 writes that the reinforcement is not considered to prevent the tile 

 from cracking, but it does prevent the tile from collapsing in case 

 cracks occur. Despite these discouraging reports, it is believed 

 that a technique can be found for making reinforcement effective in 

 packer-head pipe. The action of the trowel compacts the mortar 

 to so great an extent that it appears to have the consistency of 

 jelly, and this should be enough to create a bond between the 

 cement and steel. It may be that the curing process in the open 

 air permits the cement to break from the steel through shrinking. 

 The author was able to make but a few tests, and believes that 

 full investigation will reveal a method of successfully reinforcing 

 McCracken and other similar pipe. 



