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A Crane 120-ton All-hydraulic Trailer

29th June 1951, Page 91
29th June 1951
Page 91
Page 91, 29th June 1951 — A Crane 120-ton All-hydraulic Trailer
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A Crane Design Embodying Hydraulic Suspension, Auxiliary Steering and jacking, and an Air-Operated Braking System

AMOST remarkable trailer for heavy indivisible loads has been built by"Cranes (Dereham), Ltd.. Dereham, Norfolk, for Robert Wynn and Sons, Ltd., Newport. Constructed to carry loads of ' approximately 120 tons, the trailer has hydraulic suspension, hydraulic auxiliary steering, and hydraulic jacks, all of which are operated by electrically driven pumps. Other revolutionary.. details of this exceptional outfit inelude two bogies, each with four axles, which can be turned through 180 degrees, adjustment in width of the frame for different sizes of load, and 'special arrangements incorporated for easy loading.

The main frame is suspended between two bogies, each of which has eight wheels with 16.00 by 20-in. 24-ply tyres, and the whole vehicle consists of the bogies, two swan necks, and the main frame. A variety of frames which may be longer, higher or different in other respects, can be used with the bogies.

The swan necks are designed with 'shovel-mouth lower ends, the latter being arranged to encase the ends of the main frame when travelling. They are held to the longitudinal frame by two turnbuckles, and these can be fitted either on the inside of the frame or, when all space between the members is required, on the outside.

Torsional Rigidity Both swan necks and main frame members can be assembled for any particular load to give overall widths varying from 4 ft. 6 ins. to 15 ft. 6 ins. There are six sets of cross tubes which can be assembled either singly or in combination to give the varying width of frame. Torsional rigidity of the frame and swan necks has been assured by employing box-section members.

The frame of each bogie is approximately 1 ft. 6 ins, deep and provision is made for fitting outriggers at each corner, to attach the frame members and swan necks when these are extended to the maximum width.

There are four short axles to each bogie, and each of these is pivoted at the centre to allow individual movement to ground contour. Above the centre of each axle is a 9-in.-diameter hydraulic ram, which can rise or fall as necessary either to lift or lower.the load to pass over humped-backed bridges or to clear low railway arches. The rams are also seif-adjusting, to allow the flow of oil from the front cylinders to the rear, or vice versa, as needed to equalize the load on each tyre.

If required, one side of the frame can be raised or lowered, thus tilting the load should ths be required for clear

ance or balance. The plunger movement is vertical, because the cylinder is arranged to rotate with the axle when steering.

No Flexible Connections

At the head of each cylinder the fluid passes through a Crane-designed rotary joint, obviating the need for flexible hose. Each piston has a Gaco seal at its head and a ring which prevents air being drawn in should the axle 'suddenly sink into a hole in the road. This would result in the flow of oil being too slow and might produce a partial vacuum.

Both bogies can be steered in any one direction at the same time, and the four axles comprising each bogie can be turned through 90 degrees in either direction by a second hydraulic system, or -by drawbar control. Generally, the rear of the trailer will be separately controlled by a steersman riding on a small platform at the tail. Simple controls are arranged at this point to bring hydraulic steering cylinders into action by trimming one of a pair of three-way valves.

All four axles can pivot simultaneously through 180. degrees, this movement being brought about by .a system of chain steering, which couples all four cylinder heads together and is operated from the drawbar post. Each link of the chain is of sufficient length to pass along one side of each of the

chainwheels which are, in effect, or square construction. This makes it possible to include a positive pinning position to each of the steering heads.

At the top of each cylinder there is a large ball-bearing of angular-contact type, which transmits the full load Of 20 tons to each axle. The ram is prevented from turning in the cylinder by a triangular linkage. Both ends of the vehicle are identical, the front being steered as well as towed by a triangular drawbar, but the tear is steered, either by a tractor at the rear of the trailer or by the manually controlled hydraulic;

actuation. The trailer can be turned completely within a circle of approximately its own length, or can be moved bodily sideways by the use of two tractors, Each bogie is equipped with a sixcylindered high-speed pump which develops a fluid pressure of 2.400 lb. per sq. in. Driven by a 230-volt a.c. motor, one of these units can be brought into use in a few seconds to operate either the steering or axle cylinders. Power from the main supply can be used when the trailer is being loaded or unloaded at a factory or power station, but a small petrol engine and alternator are fitted for use where external power is not available.

The Braking System The brakes are controlled by air cylinders operated by a Bendix Westinghouse two-line system, and all 16 wheels can be braked from either bogie. There are individual brake linkages to each axle, and because of the 180-degree steering, there is little clearance between the tyres and the casing of the vertical cylinder with the wheels in certain positions. The employment of hoses between the bogie frame and axle is therefore ruled out. In the Crane design an air duct is provided in the hydraulic cylinder and a flexible hose at the head allows for steering movement. A further hose connects the duct with the air cylinder to allow for the rise and fall of the axle and piston assembly. The brakes are Girling two-leading-shoe pattern, with 16i-in.-diameter drums and 6-in.-wide shoes arranged for selfenergizing operation in both directions.

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Locations: Newport

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