ROAD AND STREET MACHINERY, appliances used in the preparation and preservation of roads are of various types and may be classified as under: Plows and Scrapers.—Plowz used in this work are of the ordinary pattern and call for no detailed description. Scrapers usually consist of a steel blade, mounted between two wheels, and so contrived that its cutting depth and in clination are capable of adjustment. A special type of plow is known as a grader. This machine cuts into the earth and loosens it, and then lifts it on to a moving belt which conveys it to the roadway.
Stone Crushers are described in detail under "Grinding, Crushing and Pulver izing Machinery.' They are used in re ducing large stones to a size suitable either for surfacing macadam roads, or for mixing with cement in the prepara tion of concrete.
Rollers, although now very familiar, are of comparatively recent origin, the first road roller being constructed in 1787 in France. Their obvious use is to compress the road-bed and upper lay ers, in order to produce a hard, durable and smooth surface. Steam rollers are commonly seen in the United States, but motor driven and horse drawn rollers are also used. Steam rollers may weigh as much as 20 tons, but the lighter horse drawn machines sometimes do not exceed 2 tons.
Spreaders consist of a container, in which the load of stones is carried, and which can be tilted to any desired angle. In this way the quantity of stone dumped on to the road may be ad justed. Behind the container is a drag with a movable scraper, by means of which the depth of stones may be reg ulated.
Sprinklers are used for spreading wa ter, oils and various tarry preparations on the surface of roads, in order to lay dust and produce a more even and less easily pulverized surface. They consist of a tank, mounted on wheels, carrying a perforated pipe behind. Modern sprin klers are sometimes fitted with steam boilers for heating the liquid, and with air compressors, by means of which the material may be forced through nozzles in a spray.
Sweepers and Scrapers, used in clean ing streets, are of various types. The sweepers usually consist of a cylindrical brush, which revolves as the framework on which it is mounted is hauled along. More elaborate machines pick up the dirt as it is swept by the brush, some by means of a conveyor, others by means of a suction device, similar to the well known vacuum cleaner. Most of these machines are horse drawn, but motor vehicles are also in use. Scrapers may consist of a row of curved blades at tached to movable rods which enable the blades to yield to irregularities in the surface of the road. Small, manual types are familiar, as well as larger horse-drawn machines.
Scarifiers are used in loosening the surface of macadam roads, when under repair. They are of various patterns, but consist essentially of metal spikes which scrape or drill into the road to a depth sufficient to loosen the surface. The spikes are sometimes fixed to the front of steam rollers.