Concrete Roads
and Their Construction

MECHANICAL DEVICES FOR MAKING ROADS 125 have now been modified so as either to remove a relatively thin slice of material or to cut their way through a hill. When used for levelling a rough piece of country—as in working a wholly new road or in widening an existing one—steam-shovels are found to be much cheaper and quicker than hand-digging, and far less super- vision is required. A British firm of steam-shovel manufacturers is Ruston and Hornsby, Ltd., Lincoln, whose No. 5 Excavator (Fig. 78), by reason of its remarkable mobility, wide range of move- ments, ease of control and general utility is particularly suitable for road-making. This excavator is capable of taking a maximum depth of cut of 20 ft. without breaking the top down, by hand, and will also successfully deal with very shallow cuts for grading, With the standard bucket-arms this machine can excavate a trench to a depth of 6 ft., and, by the simple expedient of letting out the jib ties and fitting slightly longer bucket-arms, up to 12 ft. The minimum bottom width of cut with 1 to 1 slopes is 12 ft., and the maximum height of open bucket door from rail level 12 ft. 9 in., the maximum and minimum discharging centres being 22 ft. and 15 ft. respectively. Small revolving steam-shovels have been in use in the United States for road-making with great success. The sizes which are most popular are equipped with dippers of | or | cu. yds. capacity. Two such dippers full of material woüld com- pletely fill the ordinary tip wagon or cart, while three dippers would load a 2-yd. wagon or cart to its maximum capacity. The shovels revolve through a full circle, permitting the ma- chine to dig or dump at any angle and enabling them to operate successfully in limited space. The latter feature is especially valuable when it is necessary to build one-half of a roadway while the other half is open for traffic. These steam-navvies will excavate any materials which can be penetrated by picks and shovels, and they are also valuable in handling properly blasted rock. The shovels have capacities in ordinary roadwork varying from 15 to 60 cu. yds. per hour, depending on the depth of cut, class of material, and manner in which disposal of the material is organ- ized. Traction wheels are generally used on this class of navvy, but any of them can be equipped with standard gauge car wheels, and on some of the shovels continuous tread traction can be substi-