Twin miniature arm ground signal
Entry posted by wenlock
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To complete the signalling on my layout I need something to control the exit of traffic from the exchange siding across the double slip. One route leads out onto the main and the other onto a short head shunt, so two arms would be required. I could have employed another twin arm siding signal similar to the one that controls the exit of the loop, but liked the idea of a ground signal to add a bit of variety. As my layout is set in Edwardian times it predates ground signals using discs to indicate routes. In thIs period miniature arms on short posts were used to to control stock movements. I searched around to find a suitable kit that I could use to build a 7mm scale version, but unfortunately nothing appears to be available. I suppose there probably isn't a huge market for a GWR signal that was obsolete 100 years ago!
I decided that the only option was to have a go at scratch building something to represent this long gone esoteric beastie:-)
I want the signal to be operational and plan on using servos to control the arms in a similar fashion to the other signals on the layout. For this reason I decided to construct it from brass which should have adequate strength despite the small size of the components.
One of the features of this type of ground signal were the position of the balance weights. Most GWR signals that I've seen have these weights fitted to the external walls of the post, however this type of ground signal has them set inside an arched housing at the base of the post.
I started construction by soldering three lengths of square brass tubing together and then filling out the U shaped slot in the base of the thicker piece.
Brass tubing soldered together
Balance weights were cobbled together using left over components from the MSE kits that I used to build the other signals on the layout. A pivot hole was drilled through the wide section of the post, so that a 0.7mm wire could be inserted through the post and the two balance weights to hold them in position. A flat piece of brass was also cut and soldered to the base of the post to allow the signal to be installed on the layout and stop it falling over during construction! Small L shaped pieces of brass were then soldered to the post so that lamps could be mounted on them later on.
Post, base and balance weights
The brass wire was threaded through the post and balance weights and then carefully fixed in position. I chickened out of using solder for fear of gumming the whole thing solid and instead used 5 minute epoxy resin, with Vaseline as a barrier on the pivot points. Lamps were found in my bits box and once again fixed in position again using epoxy resin.
Weights and lamps in situ
Small sections of tubing were cut to act as spacers to make sure the signal arm cleared the lamp lens during rotation.
Tubing and pivot wire
The signal arms were cut from pieces of scrap brass fret left over from my Dean Goods project, it just goes to show never throw anything away! The arms were drilled to take an 0.8mm wire and then brass wire was used to form the pivot points. Operating wires were bent from 0.5mm wire and clearances were checked during movement of the arms.
Arms and operating wires
Once I was satisfied that things worked as they should I could make a start on making the arm look more like a GWR miniature arm.
The lenses were cut from coloured acetate sheet available from Model Signal Engineering. I sharpened the inside edge of a piece of brass tubing and found by twisting this on top of the acetate it was fairly easy to cut out circles that could be used to form the signal arm lenses.
Acetate lenses
Notches were cut into the brass arm to allow the fitting of the lenses using a 2mm abrasive bur. The signal arms have a raised border around their edge and I formed this by using cyanoacrylate to glue Plastikard microstrip around the edges of the brass signal arm.
Addition of lenses and raised edging
The raised border around the arm also continues round the signal arm's lenses. I made curved sections of Plastikard microstrip by wrapping a length around a 2mm diameter bur and then placing it in boiling water. Once the water had cooled down the plastic strip had thermoformed into a permanent curve.
Plasticard strip around bur
Sections of the curved microstrip were cut and then glued into position around the lens using cyanoacrylate glue.
Sections of curved plasticard strip
After much fiddling and a bit of light sanding with an old nail file "borrowed" from Mrs Wenlock the arm started looking quite promising, so the same technique was used to make the second arm.
Finished arm
The signal was then primed with an acid etch primer and painted using Humbrol enamels. I've painted the post in my interpretation of "Torbay Bright" which I hope is appropriate and convincing!
Finished signal ready for installation on layout
The next step is to mount the signal alongside the double slip on the layout, but I think I've gone on enough for one post, so we'll leave that for another day
Best wishes
Dave
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