HIGH-PRESSURE TAR-SPRAYING OF ROADS.
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A New Type of Self-contained Municipal Vehicle Which Enables Certain Road Operations to be Effected with Economy and Expedition.
'INURING the past decade or so methods of road making and repairing have undergone a remarkable change. Clumsy and cumbersome plant, much of it necessarily man-operated and very slow in its use and application, has been superseded by mechanically operated equipment, which possesses i manifold advantages and is capable of effecting many economies, apart from speeding up the work considerably. If one has any doubts as to the acknowledged value of the motor vehicle in connection with diverse highway operations, he should pay a visit to the scene of works where such activities as road construction, widening, re-surfacing, draining, tar-spraying, and the like will afford ample evidence of the all-round efficiency of _petrol and steam vehicles in different guises and of other mechanical paraphernalia.
A few years age the lumbering horsecart held supreme sway in the matter of road excavation and similar operations, but the march of time and the progress of its mechanical successor have rought a complete change in the methods of undertaking such tasks; likewise has much mechanical plant whieh was hauled by horses been almost eliminated and in its place has appeared the self-contained power-operated vehicle.
Such a vehicle, and one that is destined to meet with increasing approval at the hands of municipal authorities, so soon as its merits become known, is the mechanical tar-sprayer. Mechanical tar-spraying machines may not be new, and attachments are available for fitting to motor vehicles, but, in spite of this, primitive and wasteful methods are still employed by some authorities.
Local authorities that have the interests of the ratepayers at heart and are desirous of carrying out tar-spraying operations with expedition and at low cost will look with favour on the type of vehicle which is illustrated on this page. Our pictures show an Aitken patent sprayer mounted on a Mann steam wagon, and recently shipped to New Zealand by Mann's Patent Steam Cart and Wagon Co., Ltd., of Leeds, on behalf of the Aitken Taroads Syndicate, Ltd., of 29, St. Vincent. Place, Glasgow, for use in connection with road work.
With this system of spraying, the tar, or bituminous compound, is sprayed whilst hot under a pressure of about 200 lb. per square inch through the special design of nipple, which gives a finely atomized, fan-shaped jet, and, moreover, as a result af the form of the nipples, effects, this operation without. destroying the velocity due to the pressure in the receiver. By this means a very considerable penetration into the joints of water-bound macadamized roads is obtained, oi when a road is being resurfaced the metal can be laid untarred, and then sprayed at such a pressure as to penetrate the coating of stone previous to rolling.
It will be seen that, under the rear of the machine, a doubletbarrelled twothrow pump is fitted, which is driven by a chain from the main axle, with a dog clutch for throwing it in and out of gear. This pump draws the tar from the main tank, which is of 1,000-gallon capacity, and delivers it into the pneumatic receiver disposed-transversely at the rear of the machine. The upper half of this receiver has previously been charged with air at, say, 200 lb. pressure by the same pump, and the tar is then discharged through flexible pipes to the special nipples. The rate of discharge is controlled by means of cocks operated by an attendant, who stands on the platform which is situated at the back of the vehicle.
The Mann tar-sprayer will undoubtedly give a good account of itself "Down Under,' and fully maintain the prestige of the motor vehicle products of the Mother Country.
This vehicle affords another example of the adaptability of the modern COM mercial motor vehicle for special classes of municipal service.