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Dragbox Appeal

After completing the bogie frame (phase 1) our plan is to assemble the components that sit around the dragbox at the rear of the frames.

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The dragbox is situated at the rear of the frame extensions and is the brown component you can see on the right of the image (click for a full size view). The vertical hole is where a large pin is located that engages with the locomotive/tender drawbar. The dragbox is in stock and will be fitted, together with the frame extensions, after the hornguides have been machined.

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This is a rear view of 70000 Britannia's hind beam when under overhaul. The class 7 Britannia frame assembly is very similar to class 6. Thanks to Nigel Fraser Ker for allowing us to reproduce this photo. This shows the central intermediate rubbing plate, the outer rubbing plates and the pony truck bolsters fixed to the gussets. The frame assembly is sitting on a temporary truck.

The next stage in frame assembly will be to

Hind Beam
The hind beam is a flat plate that is attached to the rear face of the dragbox. We have 2 hind beams currently sitting under the front buffer beam. One appears to have been drilled and one has a small number of holes drilled. We need to extract the hind beam and assess what work needs to be done

Status - Requires inspection
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Intermediate Rubbing Block
The Intermediate Rubbing Block is fixed centrally on the hind beam. The engine drawbar goes through the central "mouth" and 2 manganese steel liners are fixed above and below. This rubbing block presses against a similar rubbing block on the tender.

Status - CAD Drawing required prior to seeking quotation
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Outer Rubbing Plates
Two Rubbing Plates are fixed to the hind beam. The tender has 2 sprung buffers on the front face which press on these plates. Manganese liners are fixed in the rubbing area.

Status - In Stock - require inspection
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Hind Beam Gussets
On either side of the dragbox, outside of the frame extensions, a large gusset is fitted to strengthen this area. It also allows the weight of the rear of the locomotive to be transferred to the pony or trailing truck.

Status - CAD Drawing required prior to seeking quotation
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Pony Truck Bolsters
Bolted to the bottom of the gussets are 2 pony truck bolsters. This is a photo of the pattern which we have in stock. The bolster is fitted with the dome facing downwards. It engages in a cup which is free to "float" on the orange oval plates which you can see on the CAD model at the top of the page. The pony truck is a "delta" truck as the weight of the locomotive is transferred on 3 bearing areas.

Casting (in progress) - £512 (each)
Machining - £900 (each)

Status - Manufacture in Progress
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Rear Firebox Support
Bolted to the top of the of the gussets are 2 rear firebox supports. The grey component is fixed to the frames; it has a manganese liner fitted to the top face. The red component is fixed to the bottom of the firebox - you can see a 45 degree hole for the lubrication pipe. The cream components form a clamp, preventing vertical movement but allowing fore and aft movement to accommodate the boiler as it expands and contracts.

Status - CAD Drawing required prior to seeking quotation
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