ROAD-BUILDING MACHINERY. In recent years there has been a great advance in the machinery employed in building earth roads. The wheelbarrow was formerly much used for short hauls, but has been superseded by some form of drag scraper (§ 137) drawn by horses, and is never used now except for very small jobs, or in wet and swampy places. Formerly an embankment was constructed with plows and drag scrapers (Fig. 15, page 97), while now it is built much more cheaply and better with either the "road machine," "road grader," scraping grader (Fig. 24, page 102), or with the ck vating grader (Fig. 35, page 110). Years ago earth was thrown into wagons or carts by hand and hauled to its destination, while now it is moved with wheel scrapers (Fig. 21, page 101). Earth was formerly moved considerable distances with the drag scraper, while now the wheel scraper is employed. Formerly the surface of the excavation was finished with the drag scoop-scraper, while now it is done much better and more cheaply with the tongue scraper (Fig. 18, page 98) or the scraping grader.
There are a variety of plows, dump carts, wagons, etc., used in moving earth, which need not be considered here. The dump cart is much in favor in the New England States, but is never used in the Mississippi Valley. The steam shovel and dump cars afford the most economical method of handling earth when the amount to be moved justifies the outlay for the plant; but as that would seldom be the case in highway work, this method will not be considered.
Drag Scrapers. There are three forms of the drag scraper —the scoop (Fig. 15), the flat-bottomed pole-scraper (Fig. 18, page 98), and the buck scraper (Fig. 19, page 99).
The scoop scraper, Fig. 15, is made in three sizes. The smallest, for one horse, has a capacity of 3 cubic feet; and the two larger sizes, for two horses, have a capacity of 5 and 7 feet respect ively. Some have metal runners on the bottom, Fig. 16, and others have practically a double bottom, Fig. 17, which decreases draft and increases durability. The best forms without runners
cost about $6.00, $6.50, and $7.00 for the different sizes respect ively. Runners do not add more than 50 cents to the above prices, and the double bottom, not more than $1.00.
The scoop scraper is much used for moving earth short distances; but with it there is difficulty in building a bank of uniform solidity, since each scraperful is deposited in a compact mass by itself, with low loose places between them. Nor is the scoop scraper suitable for finishing an embankment, since the surface made with it is a succession of humps and hollows which is very trying to drive over when dry, and when it rains the low places fill with water which speedily softens the remainder of the road, and finally produces mud holes. The tongue scraper (§ 139) is much preferable for finishing the surface.
The scoop scraper is sometimes employed in loading wagons. This is done by building an elevated platform under which the wagons are driven, and to the top of which the earth is drawn in a scoop scraper upon an inclined runway. In the middle of the plat form is a hole through which the scraper is dumped. To decrease the height of the platform, the trackway under the platform is excavated. This arrangement of platform and runways is called a trap.
The pole or tongue scraper, Fig. 18, is ordinarily used for leveling up the road surface in excavations, and is frequently employed in preparing the subgrade for pavements. It may be used to transport earth short distances, but is not so good for this purpose as the scoop scraper. It is made in two sizes, 36 and 48 inches wide, which cost about $6.00 and $7.00 respectively, f. o. b. factory.
The buck scraper, Fig. 19 and 20, is the outgrowth of experience in irrigation, and has some advantages over the com mon scoop scraper. (1) The proportions of the buck scraper are such that it is more readily loaded to its full capacity. (2) It dis tributes the earth on the bank better, as it can be adjusted to deliver in layers from 1 to 12 inches thick. (3) The runners make it more durable. (4) It is more easily loaded. (5) It will follow up a steep bank without dumping, and hence runways are not required.