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A.E,C. Chassis-less Trolleybus Progress

13th April 1940, Page 23
13th April 1940
Page 23
Page 23, 13th April 1940 — A.E,C. Chassis-less Trolleybus Progress
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Fleet of 25 "Unit-construction Weymatznbodied Vehicles Placed in Service by L.P .T .B. —Bodies Directly and Permanently Attached

to Chassis

ANexperimental so-called " chassisless " trolleybus was built by the Associated Equipment Co., Ltd., in February, 1938, and placed in service by the London Passenger Transport Board. As a result of its behaviour and the experience thus gained, 25 more were built and these have recently been allocated to the Board's West Ham depot. They have bodies by Weymann's Motor Bodies, Ltd., Addlestone.

Of unit construction, these vehicles have as a main principle the rigid connection of the body side pillars to the main frame. The cross-members are extended to form outriggers to which the side pillars are rigidly attached. Normal floor bearers are eliminated. By this arrangement the strength of the whole is enhanced, with a saving in weight.

For the frame, light deep pressed members are used, the thickness being little more than half that of the conventional chassis frame. Where stresses are high, angle-pieces are inserted and riveted in position. Unnecessary metal is removed by trepanned holes in both side-members and cross-members. , The ends of the outrigger brackets are similar to the design of the

orthodox body cross-sill, and the pillars are attached in the normal manner. A notable point is the absence of welding. In the corner between pillar and outrigger a light angle member gives reinforcement.

It is stated that a feature

of this " unit-construction" design is that it

permits the use of bodies of various makes and with different pillar sections, with the A.E.C. underframe.

On the bulkhead is a flat foot, which is arranged to .coincide with a similar top flange on the frame cross-member below it. The two are riveted together. At the rear of the frame is a deep crossmember, running the full width of the body, which serves, in addition to its chief function, as a step riser and as .a strong bulkhead for the attachment of corner and door pillars.

The design takes adequate advantage of the rigidity of the body side structure to augment the strength of the underframe. No mean difficulties face designers of chassis-less buses, in which entire reliance is placed upon the girder effeet of body sides, for a number of reasons. On a laden six-wheeled trolleybus, loading amounting to over 8 tons is concentrated at two points at the bogie attachment and at the front the figure exceeds 5 tons.

Not only is the body-side girder of reduced depth at the rear points of maximum loading, but also there is an appreciable lateral distance— about 18 ins.—between the side and the point of application of the force, so that a twisting moment is introduced.

With regard to the front end, the wheel-arch on the near side cuts deeply into the body side girder, whilst the door of the driver's cab breaks right through the girder on the off side.

Conclusions as to the relative advantages and disadvantages of " chassisless " construction arrived at as a result of the experience gained may be summarized as follows:—

Gains ensue from the overcoming of body-holding-down difficulties, weight saved, longer life and easier maintenance. Losses follow from the fact that such construction is practicable only on a large scale, that modifications to suit express requirements cannot readily be made and that the body cannot be removed from the chassis.

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