File:Descriptive catalogue of the road models of the Office of Public Roads (1913) (14595081059).jpg

Identifier: descriptivecatal47unit (find matches)
Title: Descriptive catalogue of the road models of the Office of Public Roads
Year: 1913 (1910s)
Authors: United States. Bureau of Public Roads
Subjects: Roads Models
Publisher: Washington : U.S. Dept. of Agriculture, Office of Public Roads : G.P.O.
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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^ the distance betweenthe jaw plates at the lower edge. The gyratory crusher consists of a solid conical iron shaft, sup-porting a heavy mass somewhat like an inverted bell. By means of 28 DESCRIPTIVE CATALOGUE OF ROAD MODELS. an eccentric a rotary motion is given the shaft so that every point ofits surface is successively brought near the surface of the bell, andthe rock caught between the shaft and bell is crushed. The gyratory crusher will not produce as many flat pieces or tail-ings as the jaw crusher, because the stones must come in contact withtwo curved surfaces at the same time before they are broken. ROAD GRADERS. Figure 1 shows in miniature a machine which is used in buildingearth roads and in preparing the subgrade for macadam roads. Theframe, which is on wheels, supports an adjustable scraper blade, thefront end of which may be used to plow a furrow, while the rear end
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Fig. 1.—Model of road grader. pushes the earth toward the center or distributes it, smoothly. Theblade may be set at any angle or tilted either backward or forward. In building the earth road with the road machine a furrow is firsiploAved with the point, of the blade where the outside of the ditch isto be located. The blade may be made to penetrate hard or stonyground by elevating the rear end considerably and by using only thepoint of the blade for such plowing. The team should be driven so that the point of the blade will followthe furrow made on the first trip, plowing a full furrow with theadvance end of the blade and with the rear end dropped somewhatlower than before. The machine should be guided gradually toward the middle of theroad, so that it will move the earth previously plowed toward thecenter. This is done by slightly elevating the rear end of the blade ROAD MACHINERY. 29 to allow the earth to distribute under it and to give the necessarycrown to the sides of the road.

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