Fig. 108.—Cross Section of Retaining Wall. New York Central Terminal Work.
Fig. 109.—Portable Concrete Mixing Tower, N. Y. Central Terminal Work.
GRAND CENTRAL TERMINAL, NEW YORK, N. Y.—In building a retaining wall of the cross-section, shown in Fig. 108, a traveling tower moving on tracks parallel to the wall contained the concrete mixing plant. The construction of the tower is shown in Fig. 109. The tower had two platforms, one at the top carrying two 10-cu. yd. bins for sand and stone and the other directly below carrying 40 cu. ft. (4 cu. ft. cement, 12 cu. ft. sand and 24 cu. ft. stone) Ransome mixer driven by a 30 H.P. motor and a Lidgerwood motor hoist. The elevator tower carried two 40-cu. ft. Ransome dumping buckets traveling in guides and dumping automatically into the bins. These buckets were operated by the Lidgerwood motor hoist on the mixer platform. Sand and broken stone on flat cars were brought alongside the tower. The sand was shoveled direct from the car into the sand bucket, but the broken stone was shoveled into wheelbarrows which were wheeled over a light bridging from car to bucket and dumped. Wheelbarrows were used for handling the stone chiefly because the capacity of the plant was so great that enough men could not be worked in the limited space around the bucket to keep up the supply by shoveling. The wheelbarrow work added materially to the cost. Cement was carried from the cars to the sand bucket, hoisted and stored on the mixer platform which provided storage room for 100 bags. A 1-3-6 mixture was used; the sand and stone were chuted directly from the bins to the charging hopper and the cement was charged by hand. The mixed concrete was delivered to two 1 cu. yd. dump cars running on a 2-ft. gage track laid in sections on thecross pieces connecting the uprights of the forms. The track had no switches, so that one car had to wait for the other. Four men were required to push each car and two more men assisted in dumping the car and kept the track clear. The wall was built in sections 51 ft. long, each containing 250 cu. yds. One of these sections was filled in 8 hours with ease and by a little hustling a section was filled in 6¾ hours, which is at the rate of 37 cu. yds. of concrete per hour. Working 8 hours per day the cost of mixing, transporting and placing concrete with this mixing plant, with wages for common labor of $1.50 per day, was as follows:
| Total. | Per cu. yd. | |
| 2 men carrying cement | $3.00 | $0.012 |
| 6 men shoveling sand | 9.00 | 0.036 |
| 17 men shoveling stone | 25.00 | 0.100 |
| 11 men wheeling stone | 16.00 | 0.064 |
| 2 men at stone and sand bins | 3.00 | 0.012 |
| 2 men opening cement bags | 3.00 | 0.012 |
| 1 man dumping hopper | 1.50 | 0.006 |
| 1 man dumping mixer | 1.50 | 0.006 |
| 1 man cleaning chute, mixer, etc. | 1.50 | 0.006 |
| 1 motorman or engineer | 3.00 | 0.012 |
| ——— | ——— | |
| Total labor mixing | $66.50 | $0.266 |
| 8 men pushing 2 cars | 12.00 | 0.048 |
| 2 men cleaning track, etc. | 3.00 | 0.012 |
| 7 men spading concrete | 10.50 | 0.042 |
| ——— | ——— | |
| Total labor transporting, placing | $ 25.50 | $0.102 |
| 1 foreman | 5.00 | 0.020 |
| Electricity estimated | 7.00 | 0.028 |
| ——— | ——— | |
| Total general | $ 12.00 | $0.048 |
| Grand total | $104.00 | $0.416 |
It will be noted that the cost of shoveling and wheeling the broken stone amounts to 16.4 cts. per cu. yd., or nearly 40 per cent. of the total cost of mixing and placing. The cost of spading the concrete is also high for a sloppy mixture, but is probably accounted for by the fact that the concrete had to be spaded so as to have 2 or 3 ins. of clear mortar next the forms. The forms used in constructing the wall are shown by Figs. 110 and 111. They were made in panels 51 ft. long and a locomotive crane was used to shift the panels. This crane worked handling forms only a small part of the time, but a form gang of 10 carpenters was kept busy all of the time moving and reassembling. Assuming the work of the crane to amount to $5 per day and the wages of the carpenter gang to amount to $25, we get a cost of 12 cts. per cubic yard of concrete for shifting forms. It should be noted carefully that the costs given for this work do not include cost of materials, interest on plant, superintendence and other items.
Fig. 110.—End View of Forms for Retaining Wall, New York Central Terminal Work.