Turnout Operating Units - 1 of 4

I’ve been asked to do a write-up of the Turnout Operating Units that I am using on my P4 demo board.  I wasn’t going to do this until they had been installed and satisfactorily operating, although I had done a “finger-driven” test of how effectively they work.

These are certainly not an original idea.  I believe that the original Protofour TOU was produced on a similar concept, using sliding plastic curtain rail to provide the base.  The main criteria that I wanted to meet were:

• Mounted below the baseboard
• Cheap and easy to produce
• Robust but not necessary to be “engineered”
• Did not need to be relied on for gauging the switch rails

Turning to the last point, my philosophy was that these TOUs would drive the switch rails with an approximation of the correct gap between them.  However for the precise gauging I am using a “semi-cosmetic” tie-bar.  I use the term semi-cosmetic, as primarily the role is to look authentic, but it will also provide the exactness of the distance between the rails that cannot be produced from a flexible drive mechanism three or four centimetres below the railhead.

The materials used are all very commonplace.  You may have them already.  If not, all of them are readily available from Derek Russan at Eileen’s Emporium, and no doubt other suppliers.  I just know that Derek definitely does have everything available as that’s where I got most of my components from!  Usual disclaimer, no connection, etc.  The list is:

• Copper-clad sleeper strip. I had offcuts from track-building to use.
• Fine bore brass tube.  By fine, I mean something that will take a 0.45mm brass wire down the inside and be a sliding fit.  My tube came from some left-over from a High Level Models kit.
• Straight 0.45mm brass or nickel silver wire.  The sort that comes in 12” lengths from various sources.
• Thick plasticard.  I used some 60 thou that I had in the drawer, but the thickness is not critical as it is used to provide a robust mounting base.
• Two sizes of square Plastruct tube.  One that is a loose sliding fit inside the other.  The dimensions, again, are  not critical, and I believe that I used 5/16” and ¼” for my TOU. 

This is the tube that I used.  As they always say, other makes and flavours are available.  The TOU’s themselves are roughly seven centimetres in width, so you can make a number of the units from the two strips in each packet.

(to be continued...)