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Compressed-air Tipping Gear
HOLDING the opinion that there is a big demand for a power tipping gear which costs little more than a similar hand-operated' mechanism, Hamilton Motors (London), Ltd., 466-490, Edgware Road, London, W.2, has evolved an apparatus which is believed to be the first tipping gear that works on compressed air. We understand that it will be in production on May 1.
Designated the Timed patent pneumatic tipping gear, it is the invention of Mr. W. D. L. Theed, a member of the staff of Hamilton Motors, which concern holds the marketing rights. Built, at present, solely for Bedford 30-cwt, and 2-ton short-wheelbase chassis, the Theed gear is, normally, marketed as a complete tipping body which costs, all told, £39, this figure Including the cost of fitting. Thus Bedford 30-cwt. and 2-ton lorries equipped with the Theca pneumatic tipping mechanism cost £239 and £262 respectively. The dimensions of the standard general-purpose body are :8 ft. 3 ins. by 6 ft. 5 ins. by 1 ft. 6 ins. A ballast body is available with lower sides. The normal equipment includes a top-hinged tailboard having automatic releasing gear ; hand-releasing gear is optional.
Existing Bedford chassis can be converted, but when this is done new bodies will probably have to be fitted. For other chassis of :30-cwt. and 2-ton , capacities it is hoped that the• pneumatic tipping gear will be available within a month or two.
Any doubts as to the efficiency or re liability of this new gear should be dispelled by the fact that a prolonged test carried out during a period of strenuous work for the Gas Light and Coke Co. failed, so we understand, to reveal any weakness in the mechanism, and we are informed that it is capable of tipping a load more than 50 per cent, in excess of the nominal pay-load.
Briefly to describe the apparatus, a single-cylindered air-cooled pump is driven from the gearbox by a proprietary power take-off. Air is pumped to a three-way valve situated accessibly on the near side of the driver's seat.
The three positions are : (1) To direct air to the ram: (2) to hold the ram and divert the air directly to the exhaust to which a service line can be connected; (3) to lower the ram, that is; to put the ram cylinder in direct communication with the exhaust, the pipe restricting the air flow and thereby affording the necessary cushioning for lowering the body without shock.
The connections are of flexible 1-in. armoured tubing and heavy-gauge copper pipe.
Of thh non-telescopic, single-stroke type, the ram cylinder is 44 ins. bore. Air enters through the hollow piston rod, the normal working pressure being about 200 lb. per sq. in. The cylinder is attached by arms and trunnions to the front end of the body, whilst the bottom end of the rod is secured to an extra cross-member by a ball joint.
It should be noted that the socket is placed in the channel of the crossmember, and a metal and rubber guard protects the ball joint from above—au
Important point in view of the fact that the contents of .the body might otherwise fall directly on to it. The whole joint is, of course, packed in. grease.
A leather cup-washer preserves an airtight joint between the piston and cylinder walls, and the air seal is assured by maintaining a supply of lubricant in the cup-washer nearly up to the level of the air orifice. Access to the plunger can be gained by removing with a C spanner a screwed cap which forms the upper end of the cylinder.
When the top of the tip is reached, the pump is automatically thrown out of gear by a cable operated from the rear end of the body. In order to impose the minimum practicable load upon the rani, the body is hinged at a fairly forward point, the actual dimensions being approximately 6 ft. from hinge to front end, and 2 ft. 6 ins, from hinge to rear end.
The hinge-pin is a IHn, shaft running through the longitudinal members right across the frame just behind the rear wheel, the channels being reinforced where the shaft passes. On its extended ends short arms are free to turn. These are bolted to the under member of the body, the bosses being bushed and 1i in. wide.
With the engine running at a quick tick-over, the time occupied to discharge a 3-ton load is said to be about 35 secs.
In addition to the purpose for which the Theed gear is primarily intended, the supply of compressed air can be used for inflating tyres, spray-painting, etc., the device for utilisation of the compressed air being connected to the discharge pipe. An interesting paint in this connection is that it is possible to employ the ram cylinder as an air reservoir when carrying out work of this description.