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Entries on 25-November 13

entry 25 Nov 2013, 14:43
Installing seep Point Motors

For this layout I’m using Seep PM1 point motors and, as many people find these a bit difficult to get right, I thought it might be of interest to show how I install them. Firstly, to make the later wiring a bit easier, I solder a short length of wire to each of the 6 connector tabs and terminate them in a 6-way choc-block connector strip before I install the motor below the board. This picture also shows one connected up to a MASTERswitch point controller.

The main difficulty people find with the Seep PM1 motors is getting them centralised so that the built-in frog polarity change-over functions correctly. To help with this I have a couple of little home-made tools. The first is an ordinary wooden clothes peg which is reversed and a fine slot cut into each of the two ‘legs so that the hold the actuator rod in a centred position.

The second is a small 2mm thick plastikard template which duplicates the Seep PCB with the actuator rod and fixing hole positions and has the centre lines in each direction marked on it.

This then is how I install the motor. First I temporarily lay the point in position over the top of my track template and, using the holes in the tie-bar as a guide mark the axis and actuator rod position. I then remove the point, draw lines connecting both axis marks and drill very small holes through the board. These will then become the positions of the axis points on the underside of the board. I then remove a small section of the Plastazote track bed and lay my template over the lines to mark the position of the actuator slot. I use a 3mm drill in my Dremel to stitch drill the slot and then clean it up with a small router. Finally I relay the track bed and cut a slot in it with a craft knife directly above the drilled out slot.

I then relay the point itself and fix it down with Copydex, carefully checking that both the position and orientation are correct. Once the glue is dry I move the blades to a central position holding them in place with 2 small off-cuts of 1mm plastikard which are secured with a strip of masking tape.

Turning the board on edge I draw 2 line on the underside connecting the two pre-drilled axis holes and lay my platikard template over them to mark and drill the positions of the fixing holes. Holding the point activator rod centrally using a wooden ‘clothes peg’ tool I offer up the point motor to the underside of the board so that the activation rod passes through the board and the tie-bar. Align the point motor with the two axis lines and fix the motor into position. Once I am sure that the motor is centrally positioned I remove it and open out the fixing holes to form slots before re-fixing in position.

When making the final fixing, I back off the screws a quarter turn or so in order that the motor itself can move freely along the line of activation. This is important when modelling in N Gauge as the tolerance of the polarity change-over contacts is very small so by doing this the motor first moves the point blades by the 2mm 'throw' and then moves a further 1 - 1.5mm, making a total movement of 3 - 3.5mm in the actuator rod itself which ensures that the frog polarity change over contacts are fully made.

And that's about it. I didn't bother posting pictures of the underside fixing as the 4 holes drilled from the top of the board, plus the clothes peg clamp and the plastikard template are all that is needed to fix the motor position accurately now.

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