Modbury Signalling 1 - Point Dependent Ground Disc Signal
This little signal is one of the old style rotating types whereby the lamp case rotates to show a round green plate (and green light) when the road is clear or a red rectangular plate (and red light) when the road is blocked. Richard Brummitt has also made one in 2mm (http://www.rmweb.co....little-and-lit/) but being some sort of masochist he decided to illuminate his!! At a very early stage of thinking about what I wanted to model and to what extent I wanted to model it I discounted lighting up my signalling. The principle reason for that decision is simply that I feel if I were to go down that route then I would also have to add illumination to everything that would be lit from dusk til dawn, to me that included engine lamps, firebox fires, coach lighting, etc as well as the signals.
So to the task in hand... Although small I really want all of my signals to work, and this ground disc is no exception. So the first item on the agenda was to make up a TOU and the associated Memory Wire actuator for the catch point, before these were fixed in place I drilled a 6mm mounting hole for the Ground Disc housing (an 8mm length of 5.5mm diameter brass tube with double sided PCB soldered on each end and drilled through centrally to accept the ground disc pivot).
Ground Disc Housing
Once the TOU had been fixed in place and tested I was able to progress with the ground disc itself confident that the mechanism to make it rotate 90 degrees would not foul or be fouled by the TOU.
The first task was to turn up the lamp case - in 2mm scale this is some 1.5mm diameter and 1.5mm high with a further domed roof with integral "chimney" on top, the whole thing being no more than 2.5mm high. Before the lamp case was parted off from the end of a 2mm diameter brass rod I was using, a 0.7mm diameter hole was drilled up into the case to accept the pivot of nickel silver rod. The aspects of the signal were made from pieces of 0.004" nickel slier sheet, the round plate being stamped out of the sheet with a purpose made 1mm diameter punch on a piece of lead sheet, the rectangle from a 1mm strip which was sanded back to size after being soldered onto the case.
Ground Disc Lamp with the round and rectangular plates soldered in place and mounted on a 0.7mm nickel rod
The base of the ground disc was next up and included the baulk of timber to which the cast ground disc base was bolted. This item was filed up on the end of a piece of 3mm square brass bar, which had a 0.7mm hole drilled though it to accommodate the pivot rod. Before the base was separated from the bar, an area around the 0.7mm hole on the bottom was filed away to provide a recess to accommodate a small turned up washer that would be soldered in place on the pivot to prevent the lamp case moving upwards (and potentially being lost when the baseboards are up turned). Similarly a 0.3mm hole was drilled through the cast base to accommodate the point rodding that will connect it to the catch point blade.
Ground Disc Base atop a timber baulk
Once all these little components had been made, the pivot was passed through the base and secured with a tiny washer, then the base was then soldered on top of the housing (with the pivot rod passing through). Finally a small crank was made up with a 0.5mm hole just off centre and soldered below the housing in such a way as to be at 45 degrees to the plates on the lamp case - the idea being that a drive rod (attached to the TOU) will engage in the 0.5mm hole and a push of ~1mm will cause the pivot and hence the lamp case to rotate 90 degrees.
The whole upper assembly was chemically blackened (although not as black as I had hoped so I will need to go over it with a splash of paint), the faces of the round disc and rectangular plate were painted green and red respectively, the timber baulk was painted PP Track Colour (Weathered Sleepers), and the drive rod painted red (as will be all of the point rodding, FPL's, etc suitable for the Edwardian period).
The finished Point Dependent Ground Disc before locating on the layout (before touching up the parts that are supposed to be black)
Thanks for looking.