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Class 100 Gloucester RC&W 2-car DMUs

Body Sides

In an integral body of this type it is important that the vertical loads due to the weight of the structure, equipment and passengers should be distributed into, and reacted by, the whole depth of the body side including the solebars. Structurally a flat or slab body side is the ideal truss. The loading gauge excluded this possibility, since the width over panels is 9 ft. but the maximum width over solebars is limited to about 7 ft. 11 in. The problem was further complicated because the change in width from 9ft. to 7 ft. 11 in. is not gradual, but takes place almost entirely at floor level.

The transfer of load from solebars in the body side was effectively achieved by bending the pillars sharply at floor level; the pillar was actually built into the sole-bar to ensure efficient transfer of load without giving rise to sudden stress changes. Calculations showed that the forces in the pillars were at a maximum around floor level, and determined the size of pillar sections in this area. At the cantrail this size of pillar section was greater than necessary, and advantage was taken of the weight saving made possible by using a tube whose wall thickness varied. Such tubes - known as butted tubes - were readily drawn commercially being commonly used in bus seat side bends and steering columns of bicycles. The tubular pillars incorporated in this coach structure were of constant thickness over the bottom 18 inches, and the wall thickness then tapered over a length of 12 inches. Thereafter the thickness remained constant at the thinner gauge up to cantrail level. The use of this bent butted tube, for the body side pillar overcame the loading gauge problem at solebar level and it saved weight and enhanced the stability and efficiency of the body side by permitting a good pillar attachment.


For efficient use of metal, compressive strength and stability, a double tube was chosen to form the basis of a fabricated solebar. These solebars were built up by welding as units, as shown in picture on the left. The pillars were riveted to the solebars.


A stiff, deep box section was required to form the cantrail, and this was fabricated from cold formed sections generally in Corten steel. Considerable attention was paid to the connection of piIlar to cantrail since this connection was required to transfer shear into the cantraiI. This design provided a truly integral truss and without making a displeasing outside appearance. The framing members were joined by welding, with panels also attached by welding to form a unit.

The final image shows the sub-assembly of one side being assembled on a jig.

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