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Starting the bridge


Richard T

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I made a start on the branch-line bridge.

 

First up was to measure out and make the stone abutments for each side. I’d already carved away craft foam to the nearest layer down, which gave me level and known base heights (in the absence of scale theodolites a useful reference!). I then used the hot wire cutter and a craft knife to shape two rectangular blocks of craft foam, one for each end, into which I drew dressed stone outlines with a soft pencil (and forgot to photograph). These are visible—still raw— in blue in the pictures.

 

Next up were the cap timbers, 9" × 7" (actually 8 5/8" × 6 7/8", an odd measurement resulting from the 5/8" × ½" timber I ordered locally; I don't expect my modelling in this context is accurate to closer than ½" [scale] so not worried by the odd numbers!). These were cut to 7' lengths and then the four stringers, with the same cross-section, were laid across them and the track template such that each long sleeper will rest on at least one of those outermost stringers; this resulted in a neat centre-to-centre for the four stringers of 20". All are laid on edge.

 

I drilled 1 1/8" (2 mm) holes in the cap timbers, then drilled these out to 2 1/8" (4 mm) to a depth of about 3" (5½ mm). I then cut lengths of 2 mm steel threaded rod (~1" scale) such that I could bolt together the caps and stringers, with the nuts at the underside pulling in to the widened holes so the caps would still rest flat on the abutments.

 

 

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Lower abutment with cap timber.

 

 

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Upper abutment with cap timber and threaded-rod bolts in place.

 

Finally I distressed the wood a little with a wire brush, ensuring I did not overdo it.

 

The fit was perfect... now just need those sleepers to turn up! The bridge will be the second template to be built up.

 

 

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Test fit with raw abutments, and stringers cut to size and bolted to their cap timbers. The span is 15' and seven long sleepers will rest on the stringers. The bridge is in the 34' radius curve climbing at 1 in 25: true CMER style!

 

 

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Cap timbers and stringers stained. I used Ronseal “Jacobean Oak”—seemed in keeping with my Highland location—daubed on with a sponge. Weathering will come later when all is in situ.

 

 

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Test fit of the stringers, being inspected and adjusted by the Works Engineer, Doctor John. Still awaiting delivery of the scale lumber for the sleepers.

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