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Modbury Signalling 1 - Point Dependent Ground Disc Signal

Posted by Ian Smith , in Signalling 16 January 2015 · 938 views

GWR 2FS
Because I am now trying to get some of the under-board gubbins in place for the operation of the turnouts I need to get some of the above board items in place so that I can ensure that the two won't interfere with each other. One of these above-board items is the "Point Dependent Ground Disc Signal" associated with the catch point at the exit to the goods loop.

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).

Attached Image

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.

Attached Image

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.

Attached Image

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).

Attached Image

Attached Image

Attached Image

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.

Ian
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Great stuff Ian.

A disc and crossbar next then?

Regards, Andy

Fascinating, Ian, especially how the signal itself is just the tip of a much larger iceberg!

 

Any plans for a ground semaphore? (or have you already done one of those, I can't remember). I mean the ground signal that was a mini semaphore, like the one at the top of the page here: http://myweb.tiscali...igs/gndsigs.htm

Another bit of top quality modelling Ian. This layout is going to be something special.

Don

Great stuff Ian.

A disc and crossbar next then?

Regards, Andy

Andy,

Thank you.

Even those are a bit before my period, unless I have a leaning to widen my gauge at some time in the future :-)

 

 

Fascinating, Ian, especially how the signal itself is just the tip of a much larger iceberg!

 

Any plans for a ground semaphore? (or have you already done one of those, I can't remember). I mean the ground signal that was a mini semaphore, like the one at the top of the page here: http://myweb.tiscali...igs/gndsigs.htm

 

Mikkel,

Thank you.

Yes I have plans for at least one ground semaphore (and no I've not made one yet).  The ground signals with the circular white plate with red bar across are far too late for me, the slightly earlier ones with a semi-circular plate would be suitable but I do have leanings for the even earlier ground semaphore :-)

 

 

Another bit of top quality modelling Ian. This layout is going to be something special.

Don

 

Don,

Thank you.  I spent a good hour or so trying to fit the signal on the baseboard last night (and get it to rotate - which it was quite happy to do on my little test rig) without success.  I have decided that the amount of throw I thought I could get away with is insufficient so I now need to make up a little extra crank providing more throw which will be between the TOU and the signal (original plan was a direct link from TOU to signal).  Not too bothered though, coming up with (hopefully) solutions to problems is what I enjoy as it keep the old grey matter functioning now I don't have to do it at work :-)

 

Ian

Fantastic Ian! Don't suppose you fancy making a 7mm version for my Sherton Abbas! :-)
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richbrummitt
Jan 19 2015 14:24

Yes. I've wondered about how to light the trains themselves, although hadn't given any consideration to fireboxes. 

 

I've started a ground semaphore - along with the rest of the signals that I require for Littlemore. They got packed away when we moved and they are still in whatever box they went in to waiting for me to find them. They'll be moving again soon because my modelling is going to be largely housed in the garage. 

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