Cost for Haul. It is assumed that the scrapers will be worked in a gang of six, which will require one foreman, one plow, three scraper holders, and one man on the dump. The ex pense for these items will be the same as for the drag scrapers, and are so entered in Table 15, page 119. At this distance a trip will occupy 24. minutes, and a yard will be deposited every 10 min utes, or 60 yards per day, at a total cost of $3.50 or 5.83 cents per cubic yard for hauling.
The wear and tear is computed on the assumption that a scraper will last for 200 days' continuous work, making a cost for deprecia tion and repairs of, say, 20 cents per day per scraper. The wear and tear on the plow will be estimated at 30 cents per day. The total cost will then be as in Table 15.
Notice that the cost for 100 feet with the wheel scraper is 9.99 cents per cubic yard, while with the drag scraper for the same distance it is 12.67 cents. The difference is in the cost of hauling, and is due to the difference in the capacity of the two scrapers.
Cost for Haul. A trip will be made in about 4 minutes, and each scraper will put in 50 cubic yards per day. The three scraper holders can fill an additional scraper, making nine in all. The cost will then be as in Table 15.
Cost for Haul. In this case another scraper can be added, making four teams to each scraper holder. A trip can be made in about 5i minutes, and each team will move 45 yards per day. The cost will be as stated in Table 15.
Cost for Haul. It is difficult to determine the most economic distance for each size of scraper, since the several sizes are seldom available for making the test. However, at 300 feet, the cost with a No. 2 scraper is about the same as with a No.1 at 200 feet; and at 400 feet the cost with a No. 2 is about the same as with a No. 1 at 300 feet. But at 400 feet a No. 3 is more economical than a No. 2.
A snatch team is required in filling No. 3 scrapers. The extra force acquired by using the extra team completely fills the scraper, and also packs the load so that it is less liable to spill than when loaded by a single team. For this distance it is most economical to work the scrapers in a gang of eight; and two men will be re quired to hold the scrapers while being filled. Each team will put into place 45 cubic yards, or 360 for the gang. The total cost will be as shown in Table 15.
Cost for Other Distances. For each additional 100 feet of lead, add 1 cent per cubic yard to the cost of haul; and the total cost will be approximately as shown in Table 15.
When the amount of earth to be moved is considerable and the length of haul is great, something must be allowed for keeping in repair the road over which the earth is transported. A wheel scraper is prone to wear a series of humps and hollows along the road it traverses, and these must be kept in subjection, if the work is to be (lone at reasonable cost. The proper allowance will vary greatly with the soil, the weather, etc. Trautwine recommends 0.1 cent per cubic yard per 100 feet for this expense.
It is difficult to determine at what distance wagons should supersede wheel scrapers; but usually the economic limit for wheel scrapers is 600 to 800 feet, and it is seldom wise to use scrapers beyond S00 feet—unless they are at hand and wagons are not.
There is very great variation in the amount of earth a shoveler will load in a day. In well managed work, the shovelers are not actually engaged in loading much more than half of the time; while under poor management, they do not really work half of the time. With short intervals of rest equal to the working time, a man should load, in a day of 10 hours, 20 cubic yards of light sandy soil, 17 yards of loam, and 15 of heavy soil—provided all are loosened by plowing or picking. Usually five or seven men are set to load a wagon—two or three on each side and one at the rear. Seven men will load a wagon with loam in 5 minutes, 8 minutes will be con sumed in traveling to and from the dump, 1 minute in dumping, and 1 minute in getting into and out of the cut—making in all 15. minutes for a round trip; and therefore the cost for wagon and team is 8.75 cents per cubic yard, as above. In this case the team works only about half the time. If only five men are engaged in loading a wagon, 7 minutes will be consumed in loading, and the time for a round trip will be 17 minutes, and each wagon will deliver only 35 cubic yards, making the cost 10 cents per cubic yard. In this case, the team really works less than half the time. If the men shovel only 12 to 15 cubic yards each, as is very common, the loss by the wagon's waiting for a load is considerably more than the above. The proper number of men to be set to loading a wagon depends upon the relative wages of shoveler and wagon, upon the length of the haul, and upon the quantity loaded per day per man.* Usually seven shovelers are employed to each wagon, but this number is not enough to secure the greatest economy. In the fol lowing estimates it will be assumed that nine shovelers are em ployed to each wagon. At the above distance, nine shovelers, each loading 17 yards per day, will be required to keep three wagons going, each of which deposits 45 cubic yards per day. The cost of loading will then be 8.8 cents per cubic yard.