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Aylesbury - A Bridge Too Far


gazzaday

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“I need something to get my teeth into”, I said. In hindsight, I would have been better off with a Werther’s Original. Nevertheless, I decided to model the footbridge at the north end of Aylesbury station.

 

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The actual bridge itself has undergone a number of reincarnations. I managed to obtain the original drawings. Unfortunately, the original contractor decided to do his own thing, the span being some 10ft longer than the drawing depicted. Fortunately, the piers remained relatively true to form. Armed with the drawing and a number of photographs from Flickr, I decided to model the span as it stood in the 1950s. The span consisted of a square ended Pratt Truss made up from equal angles, with universal beams at each end. There were nine square sections to the truss and I estimated that each section was 8ft high, giving a total span of 72ft. Much to the delight of Eileen’s Emporium, I used 1mm brass equal angles for the main ties and struts with 0.5mm for the secondary members. By measuring the brickwork below the universal beams, I calculated the beam size as a 686 x 254; which were constructed in suitably sized Plastistruct sections.
I drafted the span to scale using Microsoft Visio software. I laid out a print of the span on an old breadboard and proceeded to set out the main brass cross beams securing them with steel pins. I had not undertaken any soldering for nearly thirty years. For an intricate piece of work of this nature, I decided to bite the bullet and invest in a decent iron. I plumbed for an Antex 690SD which offered variable temperatures shown on a digital display. I proceeded to solder the uprights to the main beams followed by diagonals. My attempts at soldering were embryonic, being that there appeared to be more solder than brass. I frustratingly chased joints around the truss like a demented Pac Man. The second span benefited from both practise and a slightly higher temperature of 300°C. The gusset plates were replicated using 0.5mm thick brass plate. Paper templates from the design drawing were stuck to the plate and the sections cut out individually with a metal cutter. It is interesting to note that none of gusset plates are the same; I suppose this is a reflection of the post war year’s construction quality. To prevent pedestrians hanging (or jumping) through the truss, the bridge was fitted with a mesh screen up to shoulder level. I recreated this using 1mm square Scale Link fret soldered to 0.3mm equal angle.

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I expected the first outing of my efforts in the Clubhouse (Risborough & District MRC) to be greeted with applause and choruses of “for he’s a jolly good fellow”. This was not to be, with the only comment being, “where are the rivets?” With renewed determination, the rivets were recreated using Archer water-slide transfers. Despite the small scale, these proved very effective. However, in future, I will apply the rivets just before the final pint coat, as some of the detail was lost.
I constructed the deck using 1mm thick Plasticard and brass composite; the brass section enabling the deck to be soldered to the bridge trusses. The asphalt surface was recreated using wet and dry paper. The truss (minus the deck) was sprayed with Tamiya primer followed by a finish coat of Humbrol Light Grey. I carefully soldered the deck to the trusses and fitted the smoke deflectors which were constructed from brass plate and angles. I received a good tip of drilling a hole through the deflector plate to enable the solder to run through to the supporting angles. Brass tacks were also soldered to the composite deck to enable positioning on the brick piers. The whole structure was suitably weathered with a light spray coating of Humbrol matt black. The finishing touches to the structure being a couple of train-spotters.
My attention now turned to the brick piers. Once again, using Microsoft Visio software, I drafted the design based upon the original drawing and historic photographs. As the intention was to utilise the laser cutter, the design had to be drafted in its constituent parts. The drawing was converted into DXF format. A week later, I was presented with the output from the laser cutter in the form individual pieces like an Airfix kit. The quality of the finished product is truly excellent, right down to the intricate masonry work which had a curve on the east pier. Details of this nature would be extremely difficult to recreate in Plasticard. I bevelled the edges of the constituent wall pieces using a rotary sander. This ensured flush edge to the wall corners. Furthermore, a club member had ingeniously included a mounting hole through each of the pieces to ensure that they lined up during the final assembly. The piers were painted with a Humbrol Orange Lining and Leather mix to match the actual finish. The finished article was weathered with matt black and stains of concrete to represent calcium deposits.
In summary, this has been a very satisfying first contribution to the club layout. My introduction to the club and this initial and challenging project has renewed my interest in railway modelling. In hindsight, there are things I would have done different. Although the end product is not a perfect recreation of the original, it looks right and more importantly puts a smile on my face. Now, where are those Werther’s Originals?

 

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Edited by gazzaday

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Brilliant modelling

 

I walked over that bridge on my way to 'the Floyd' 77- 85.

 

Superb. Now you just need to do the old Goods Shed !

 

Good work there.

 

Matt Wood

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Thanks Matt.  Can you remember what the decking consisted of?  I have assumed it was an asphalt finish.  I am sure the Goods Shed will be included in our layout.  I have just finished the South Signal Box; blog to follow.

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