December 2012 – A Bridge at last!

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December 2012 – A Bridge at last!

By Alan Price

In our last home, I had a good garden railway that kept me occupied and which saw a lot of development and evolution. Being a sloping site, the line originally began at ground level, then went to waist-height. I never got round to making the intended girder truss bridge, making do instead with a simple wooden plank hinged at one end. I bought some aluminium section with good intentions, but……

About 18 months ago we moved to a new home, requiring a new line.  This time it is all at waist-height. Again, I needed a removable section for access to the “orchard” (i.e. the small area containing a couple of fruit trees and bushes). A simple wooden bridge sufficed to get the line operational, but having a little more available time, I decided to make that truss bridge at last.

I had an idea of what I wanted, and a look at the MVL Bridges website confirmed my ideas. When I got down to making the plans, I realised that even my modest requirements would require a little more aluminium than I had purchased those years ago. Fortunately, Michael Leckenby of MVL also supplies the aluminium sections he uses at very reasonable rates, and so I was able to order what was required, which arrived very quickly.

I am no engineer, and so, even with plans, construction was a make-it-up-as-you-go-along affair. Fortunately, most things went well, but there were some hiccups on the way.  For instance, I measured my largest loco to ensure there was plenty of clearance, but as the bridge began to take shape and I added the uprights, I had a thought about the rolling stock. Mine is a dual-scale layout, running either SM32 or 1/12th scale on the same track. My sudden thought was the IP Engineering 7/8ths Guards coach with its duckets – with great dismay, I realised it would not fit the bridge as I had made it thus far!!!! Fortunately, I could easily remove the uprights by drilling out the pop rivets and by adding them to the outside of the bridge ( a much better appearance in my opinion) the aforesaid coach could negotiate the bridge – just!

The other hiccup was a minor one, in that the pop-riveter would not fit inside the bridge, and so some rivets had to be done the “other” way. This was more a matter of aesthetics, rather than anything else, but if I had planned it properly, it would have been even better in my opinion.

I started with the deck, naturally enough, with 2 lengths of 1” x 1” T-section aluminium and cross-members of 5/8” x 5/8” U-section, except for the end bearers, which were 1” x 1” angle.  2 strips of ¾” aluminium were used as diagonal bracing.  This bridge was to be hinged at one end and so the T-section was suitably cut and shaped, along with two further short pieces for the other parts of the hinges (the pictures will help you understand exactly what I mean).

To keep the sides vertical, not leaning in or out, I decided to use a method I had observed on many foot-bridges. Two of the cross bearers extended beyond the width of the deck. To these would be added diagonal braces of ¾” strip.  Meanwhile, the vertical members were added, this time being ½” square tube section. Two lengths of the 1” x 1” angle were cut and bent to go along the tops of the vertical members. (Careless measuring nearly meant a wasted length, but again I managed to rectify the matter.) Four corner plates were cut from some scrap aluminium sheet, then I added the remaining diagonal braces. (This was the point at which I realised I had to fit the pop-rivets the “wrong” way.)

Two further lengths of 1” strip were added along the length of the deck. I then had a decision to make: do I simply attach a suitable length of 32mm track, or do I attach individual chairs? Rightly or wrongly, I chose the former. The remaining touch was to add a wooden walkway on one side. Then the holes were drilled in the hinges, bolts inserted and the bridge was fixed in place.

The result is a strong, attractive-looking bridge which is easily raised and lowered, that accurately lines up with the track on either side.

Alan Price

2016-10-12T13:53:48+00:00 December 1st, 2012|Model of the Month|Comments Off on December 2012 – A Bridge at last!