Fig. 66.—Diagram Showing Method of Rolling Chenoweth Pile.
Method and Cost of Making Reinforced Concrete Piles by Rolling.—In molding reinforced concrete piles exceeding 30 or 40 ft. in length, the problem of molds or forms becomes a serious one. A pile mold 50 or 60 ft. long is not only expensive in first cost, but is costly to maintain, because of the difficulty of keeping the long lagging boards from warping. To overcome these difficulties a method of molding piles without forms has been devised and worked out practically by Mr. A. C. Chenoweth, of Brooklyn, N. Y. This method consists in rolling a sheet of concrete and wire netting into a solid cylinder on a mandril, by means of a special machine. Fig. 65 is a sketch showing a cross-section of a finished pile, in which the dotted line shows the wire netting, the hollow circle is the gas pipe mandril, and the solid circles are the longitudinal reinforcing bars.
Fig. 67.—Machine for Rolling Chenoweth Piles.
In making the pile the netting is spread flat, with the reinforcing bars attached as shown at (a), Fig. 66, and is then covered with a layer of concrete. One edge of the netting is fastened to the platform, the other edge is attached to the winding mandril. The winding operation is indicated by sketch (b), Fig. 66. Fig. 67 shows the machine for rolling the pile. It consists of a platform and a roll. The platform is mounted on wheels and is so connected up that it moves back under the roll at exactly the circumferential speed of the roll; thus the forming pile is under constant, heavy pressure between the roll and platform. When the pile has been completely rolled it is bound at intervals by wire ties; the wire for these ties is carried on spools arranged under the edge of the platform at intervals of 4 ins. for the first 10 ft. from the point and of 6 ins. for the remainder of the length. The binding is done by giving the pile two or three extra revolutions and then cutting and tying the wire; then by means of a long removable shelf which contains the flushing mortar, as the pile revolves it becomes coated on the outside with a covering that protects the ties and other surface metal. Finally the pile is rolled onto a suitable table to harden.
An exhibition pile rolled by the process described is 61 ft. long and 13 ins. in diameter. This pile was erected as a pole by hoisting with a tackle attached near one end and dragging the opposite end along the ground exactly as a timber pole would be erected. It was also suspended free by a tackle attached at the center; in this position the ends deflected 6 ins. Neither of these tests resulted in observable cracks in the pile. The pile contains eight 1-in. diameter steel bars 61 ft. long, one 2½-in. pipe also 61 ft. long, 366 sq. ft., or 40.6 sq. yds. ½-in. mesh 14 B. & S. gage wire netting, and 2 cu. yds. loose concrete. Its cost for materials and labor was as follows:
| Materials— | |
| Gravel, 28.8 cu. ft., at $1 per cu. yd. | $ 1.05 |
| Sand, 19.8 cu. ft., at $1 per cu. yd. | .73 |
| Cement, 3 bbls., at $1.60 per bbl. | 4.80 |
| Netting, 40.6 sq. yds., at 17½ cts. per sq. yd. | 7.10 |
| Rods, wire, etc., 1,826 lbs., at 2½ cts. per lb. | 45.65 |
| ———— | |
| Total | $59.33 |
| Mixing 2 cu. yds. concrete, four men one hour, at 15 cts. per hour | $ 0.60 |
| Placing concrete and netting, four men 30 mins., at 15 cts. per hour | .30 |
| Winding pile, four men 20 mins., at 15 cts. per hour | .20 |
| Removing pile, four men 10 mins., at 15 cts. per hour | .10 |
| ———— | |
| $1.20 | |
| Grand total | $60.53 |
This brings the cost of a pile of the dimensions given to about $1 per lin. ft.