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Pony Truck or Trailing Truck

For most of the photos on this page, you can click the image for a larger picture.

The "2" in the 4-6-2 Pacific locomotive wheel arrangement is the 2 wheel truck that supports the weight of the rear of the locomotive. This truck can be known as a

The British Railways drawing use the term "pony truck" so that is the term used here. The Class 7 Britannia locomotives and the original Class 6 Clan locomotives were fitted with a leaf spring pony truck. This had limited room for movement and was reported to give a hard ride. The solitary Class 8 locomotive - 71000 Duke of Gloucester was fitted with a longer travel coil spring pony truck which is reported to assist in providing a very smooth ride. This pony truck was part of the drawing set for the lot 242 Clans.

We are grateful to Michael Hughes from the BR Class 8 Steam Locomotive Trust for the reproduction of the following photos which show the pony truck from 71000 which we will need to manufacture.

Highslide JS

This is a view from the front of the pony truck showing the central front pivot. The triangular front section of the truck is a casting, the rear section is a fabrication.

Highslide JS

This is a rear view of the pony truck. The coil springs are shown, either side of the outside Timken taper roller bearing axle box. The 2 oval plates are the weight bearing areas; 2 bolster cups "float" on here which engage with bolster domes fitted at the rear of the locomotive frames. Between the 2 plates is the centring pin. This pin is bolted to the dragbox at the rear of the frame extensions and engages in a slot on the pony truck. 4 side control springs (2 either side of the pin) control the movement of the pony truck on entering curves and help recentre the truck leaving a curve. The 2 oil boxes lubricate the centring gear bushes. You can see the end of the centring gear protruding below the oil box.

Highslide JS James Conway has joined our design team and is working on deciphering the British Railways drawings. His first job was to produce a CAD model for the radial arm of the pony truck. This is a casting and here is a front view.
Highslide JS A view from the rear showing how it is joined to the pony truck fabricated frame assembly.
Highslide JS Starting to build up the fabricated frame assembly. The axle, spring beam and spring links are shown.
Highslide JS Springs and supporting gussets added
Highslide JS Side control gear added
Highslide JS A cut away showing the side control springs and gear. The centring pin engages in the bronze bush
Highslide JS Wheels added together with the fore and aft strengthening ribs.