26 



BULLETIN 463, U. S. DEPARTMENT OP AGRICULTURE. 



The rate at which earth can be excavated with an elevating grader 

 is relatively very high when conditions are favorable and the grader 

 can be kept moving. But there are a number of rather complicated 

 parts about such a machine which sometimes get out of order, 

 and the work also is hampered frequently by many unforeseen con- 

 tingencies, such as " bogging " of the wheels, choking of the plow 

 or the elevator belt, occurrence of buried stumps or stones in the 

 excavation, etc. For these reasons the actual capacity of elevating 

 graders, considered over a long period, seldom is more than about 

 one-third or one-half the rated capacity, and where the material is 

 loaded into wagons as it is excavated the actual capacity of the ma- 

 chine may be reduced still further. Elevating graders of the size 

 used ordinarily in road work have a rated capacity of about 100 

 cubic yards per hour. 



"USE OF SCRAPERS, WAGONS, ETC. 



To grade a road of any considerable length, no matter where it is 

 located, usually will require a considerable amount of work with 

 devices other than the grading machine and elevating grader. 

 The latter machines, as previously explained, may be very economi- 

 cal for special conditions to which they are adapted. But these 

 special conditions seldom prevail for more than comparatively short 

 stretches of road without sections intervening which require that a 

 relatively large volume of material be moved from excavation to em- 

 bankment within a distance of only a few hundred feet. Figure 15 

 shows a typical cross section for an earth road, where the grading 



TYPICAL CROSS SECTION FOR EARTH 



*W," width of road between ditches, npt less than 20 feet 

 *D" varies from 2 feet to 6 feet depending on the rainfall and grade. 

 ~h",' crown, varies from ^ inch to the foot for level grade to I inch to 

 the foot for a grade of 5% 



Fig. 15. 



machine hardly could be used advantageously except for finishing 

 the road surface. To accomplish work of this kind economically, 

 the devices for loosening, loading, and hauling the material must 

 all be adapted to turning around quickly in a small space and, not 

 infrequently, must be such as to be handled readily over very rough 

 ground. Such implements as wagons, wheeled scrapers, drag 

 scrapers, and plows therefore should form a part of the equipment 

 on practically all road-grading projects. 



The choice of proper implements to employ in moving material 

 from excavation to embankment depends, first, on the nature and 

 quantity of the material to be moved, and, second, on the length of 



