Friday, June 04, 2010

Adjusting screw holes

Hole fillingThe model railway in a box will be using Seep point motors as they will fit in the space available under the board. I've not fitted these before but essentially they are held in place with two (not provided) brass screws that go through holes in opposite corners of the PCB baseplate.

Toe fit, a hole has to be made in the tie bar sleeper. Then the point motor is offered up and screwed in place making sure that the centre of its throw is that same as the centre of the point throw. That way the ends of the throw will see the switch blades hard up against the stock rails and the polarity of the frog will have been switched.

All this relies on getting the fixing holes in the right place. And when you don't, like me, being able to do something about it. In this case, gluing sharpened match sticks into the badly placed holes to fill them up. The excess is cut of with some flush wire cutters and sanded flat. Then I can make new ones a few millimetre to the sides where they should have been in the first place.

Actually I did quite well. After the first motor, I had got my eye in and did the others without any problems. Or matchsticks.


Michael Campbell said...

There is an easier way ... don't bother!

As they have a nice large surface area, a coat of Bostik on the PCB base of the point motor holds it in place nicely. It can then be held in place while the point is moved back and forth, to ensure the washer "contact" for the polarity switch moves between the PCB contacts, and the operating pin is moving laterally. The position is easily adjusted while the glue is wet.

I've used this method for years - no screws at all - once set the Bostic holds them solid!

Phil Parker said...

No chance - I want to be able to take them off again when they break down !

OK, so solenoids tend to be pretty reliable but I am paranoid about this sort of thing. Mind you, if I'd messed up the hole again, at least with your method I have a reliable last resort !

Michael Campbell said...

No problem - prise them off with a screwdriver. I've never had one fail (yet!) but have taken them off a layout and re-used them!

Phil Parker said...

Sounds like brute force and ignorance to me. I could never countenance THAT sort of thing :-)