How Lorries Aid Rapid Road Construction.
Page 19
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THE rapidity with which roads are being constructed in the United States will be gathered from the fact that the total road mileage of that country is now 2,941,294. Many roads have been built of recent years, and motor lorries have done much to make this rapid growth possible.
A modern appliance which has effected considerable economies in both time and labour on highway construction in America is the Koehring paver. The machine shown in the accompanying illustration is operated by the Borough Asphalt Co. of New York, and works in conjunction with their fleet of ten Mack lorries.
The type of body used on the lorries is divided into five separate compartments, and, when in use on road work, each is loaded with a batch of dry aggregate (sand and crushed stone) at a central plant located some little distance away. 11pbn arriving at the scene of operations, the lorry backs up towards the mixing plant or paver. The body is then tipped, and, by a patented mechanical device, one of the compartments, which contains just enough material to
fill the mixer, is opened, and its contents precipitated into the hopper. Cement is then added from a wheelbarrow, the hopper raised, and the mixture poured into a large revolving drum.
To discharge the contents of the five compartments by this new method takes a matter of only six minutes, whereas, by the old system, it took five men working With shovels and wheelbarrows about three minutes to load only one batch of material on the hopper. In addition to the time-saving factor, the new scheme has enabled manual labogr to be considerably reduced, thus effecting a large saving in costs on wages and other items.
When the concrete is thoroughly mixed in the revolving drum, a slot is opened, and the mixture runs into a large steel bucket, which rides on a movable steel arm about 15 ft. long. This enables the bucket of concrete mixture to be dropped anywhere within the radius of the steel arm. Labourers then quickly spread the material, and when the 15 ft. of ground are covered the paving machine moves ahead. By this ingenious arrangement it is sometimes found possible to start work on a city block in the morning and have it fully paved with concrete by nightfall.
When the concrete has hardened sufficiently, the asphalt is ready to be laid. For this operation the partitions in the lorries are removed, and the entire body is filled with the hot asphalt. Incidentally, the bodies of the lorries are insulated with asbestos for this purpose.