Monday, August 10, 2015

Catch Point and Indicator

For some time I have been aware that I should have catch points on my layout but after looking at a number of station track plans I am not sure what the rules are for placement. They seem to be protecting sidings onto the main which is obvious (e.g. private sidings, oil/petrol sidings, etc.) and also loops but then not all loops.

Since the station yards are already in place on my layout I have decided to install a few where I have the room for them.

On the layout I have used code 70 track and points from Shinohara, Peco code 75 track and points, Micro Engineering code 70 track and a number of code 70 hand built points so I began by looking at the Peco code 75 catch points as these were the only commercially available ones I knew of.

A study of a NSWGR Standard Catch Point plan from 1936 showed that the Peco one was reasonable but not quite right.

Here is the 1936 plan:

I decided to try to draw up a 1936 catch point for 3D printing. Once again I used Sketchup a free 3D drawing program (there is also a professional version that is about US$500).

Here is a screen view of the resulting 3D model; I have done both a left and right version. The horizontal pieces are two sleeper variations that plug into the two long sleepers at the left hand end and are for mounting the catch point indicator. The small triangular piece is the hardwood block that guides the wheels up and over the rail (see plan above) and it plugs into the sleeper with the small square hole in it.

The catch point has been designed to take code 70 or code 75 rail (as long as I have measured and drawn it correctly). Of course a single point blade will have to be filed up and it would be pivoted on a fish plate. Due to the minimum wall thickness restriction of the 3D printing process for the White Strong and Flexible material the tops of the dog spikes may need to be filed slightly once the rail is in place to clear the flanges (based on flanges to NMRA RP25). Being a nylon the webs between the sleepers may be cut occasionally (every alternate web) to enable a slightly curved catch point to be made.

I haven't had one printed as yet but will probably do so soon as I will need to check that it all works before I make it available on my Signals Branch Shapeways Shop.

One reason for delaying is that I am drawing up a catch point indicator which I would like to make work off the catch point blade. The basic shape has been done but I am a bit stumped at the moment on trying to work out how to get the indicator part to rotate through 90 degrees with only a very small movement from the point blade. I guess if I can't get it to work then I will release a static version.

Catch Point Indicator at Gunning - Sourced from the Internet, Photographer unknown
The indicator will be printed in the Frosted Ultra Detail material, a translucent plastic that can be used to pipe some LED light for the aspects from below the baseboard.

You would think that this would be easy since I have an actual catch point indicator in my layout room, a 50th birthday present from my brother Noel (it came from the Tumut line - he used to live at Adelong). Unfortunately what works on the prototype may not work on a model.

I am not sure how many modellers would be interested in a lit and working catch point indicator but there is nothing like a challenge!


Australian Model Railway Magazine said...

G'day Ray :)

Catchpoint placing is very simple when you know the basic rule. Catchpoints protect the main line, so must be place anywhere a siding joints a main line. Crossing loops on single tracks are regarded as main lines, so don't have catchpoints. Everything else does where it joints a main running line.
James McInerney

Ray P said...


Thanks for the clarification.


Andrew Campbell said...

Good luck Ray, Ian And I had plans to do this on Bowen Creek but never got round to it, more or less cause it got to bloody hard. I will certainly watch with interest.