Swapsie – the childish act of swapping things according to Wiktionary.

Do you remember at school swapping a Top Trumps set for a the latest Hot Wheels car or similar? I do! I remember getting roundly b*llocked by my mum for not recognising the value of things I was giving away and (metaphorically I am pleased to say) swapping gold bars for glass beads almost like the Incas and Cortez.

In the world of toy trains, the same happens and is very useful where someone can offer something that you don’t have (or find difficult to make) in return for something you do have. This is one such example. Sitting next to Duncan Redford at an EM Gauge Society/Scalefour Society skills day a few years back demonstrating signal construction a barter was arrived at whereby I would build Duncan a signal in return for him doing some 3D design and printing. I think it is fair to say that neither of us have rushed with our respective shares of the bargain but with the next ExpoEM only a week away, I have shifted into gear to finish the started signal that was my part of the deal.

Duncan is building a GWR broad gauge era layout and wanted a close replica of a signal that the GWR Society has recreated at Didcot, but adjusted to have only a single arm. So after coming out in cold sweats about the idea of modelling anything GWR (!!!) I took a look at it. Like many signals, there are differences and similarities with other signals but after a bit of study it became clear that it was sufficiently different that a site visit to Didcot to be required.

Having measured it up including, when no one was looking, a climb to the arm/lamp to measure it, I came home to draw it. I was shocked to find that it was tiny; 3mm/1foot at best and I had a panic attack -had I mucked it up and mis-measured it. Obviously, being a professional surveyor I could not possibly have done that, could I? After a few months, the fear that I had niggled on me and so came about site visit number 2 and a further climb up the signal ladder. Nope, it really is tiny – both the post and the arm are notably smaller than I am used to.

There are several unusual aspects to the signal; the one glass spectacle plate, the tapered arm and the very pronounced stiffening around the slot in the post were all going to be key to capturing the character of the signal. So out came the computer and a small fret was added to an etching order for the arms/spectacle plates. I then formed the basic post from 4mm square section brass which I filed to a taper with a 2.5mm cross section at the top.

Despite having built a few slotted signals already, they are still pretty difficult to get to work well. The difficulty that I have had is to get a soldered joint onto the arm spindle when it is encased in the brass post around it that acts as a heat sink. On a number of occassions the joint has broken and the arm no longer operate. I was determined this was not going to happen this time and have adotped a different approach, by assembling the arm first and then mounting it within the post whilst this was being assembled.

I had filed some 4mm square section into a taper to form the full length of the post. Even though I was about to cut a section of this out, it is necessary to form the full length of the taper so that it is consistent across its full length. Once I was happy with this, i filed two pairs of slots in the outside of the post on oppposing faces. The depth of these was such that the tongue between them was the correct size for the slot in the post. I chose to mount the finial at this stage, with some 296^o solder and a lot of heat (from a minature blow torch). This is what it then looked like:

Next, I cut away the block of post that sits between the two filed sections to create a hole in my post. As there is around 2 hours of work to get the post to this point, it is a bit nerve racking chopping it like this! I then cut a pair of 1*4mm brass plate lengths to sit on the tongues and drilled both to receive a 14BA bolt. This was threaded through the first of the plates and adjusted until this a continuation of the taper of the post – this entails some filing of the metal to make the outside face match the post and plate match. It was then soldered in place, again using the 296^o solder and a blow torch, to look like this:

The photograph above shows that these plates were wider than the post, in practice the prototype acheived this by planting timbers across these sections but it is easier to do this by way of using the sider plate material.

Temporarily mounting the second plate enables the hole for the arm spindle to be formed through both parts of the arm. The arm was now attached to the spindle with more use of the 296o solder and the use of a couple of minature washers either side of the arm so that I could be confident that the joint would hold.

Releasing the second plate now allows the arm/spindle assembly to be inserted and any adjustments made to ensure that it can move freely in the slot by securing the second plate in place with a 14 BA nut. The nuts and bolts are scarificed in the build by leaving them in place for the next step because once I was happy that it was correct I soldered the second plate in place including the nuts and bolts. This time I used 145^o solder which meant that it would not disturb the first plate as I was doing this and this is what it then looks like – a slotted post with an arm within that is firmly attached to its spindle!

More to follow; including the second piece of bartering that I know someone is looking out for progress on!