PM1 point motors

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PM1 point motors

Postby Ogster » Fri Jul 01, 2016 7:13 pm


I have a number of PM1 motors dotted around the layout which work pretty well at switching point direction - Peco 75 track, DCC, OO. They were purchased with the added benefit of wiring in the frog to the inbuilt microswitch, which until today, I had not tried out. However, as locos tended to stall on one or two of the points due the blade not providing positive contact with the rail, I decided to fully wire one of them up to the frog, and of course the DCC supply, to try and eliminate the stalling and to provide an alternative method of energizing the point.

However, it does appear that the inbuilt microswitch is pretty sensitive. I had assumed the idea behind wiring in the frog is to eliminate the necessity for the blade to provide positive contact for the rail, yet even if the blade is moved even a hair's breadth away from the rail, the loco still stalls - suggesting the microswitch is de-energized.

Is it the case then that the microswitch is indeed pretty sensitive to motor position - I believe it is simply a wipe contact across the PCB of the switch - and if so, how can one adjust the PM1 so as to energize the fully wired in point even if positive contact between blade and rail is not maintained?

Secondly - is there any way of establishing whether the point is indeed energized by the frog alone and not by the positive contact between blade and rail? I have a multimeter.



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Re: PM1 point motors

Postby Flashbang » Fri Jul 01, 2016 8:18 pm

Seeps are notorious for needing to be 100% correctly alined to the point it operates.
Best way I have found is to set and hold the point blades mid way with the aid of some card shims or other items to equal the blades. Then retain the Seep half way in its travel using the "Seep cloths peg" idea. Then fit the motor absolutely in line with the moving points tie bar and centered. Once positioned carefully fix in place with suitably sized screws.

Try post 5 here for the Seep peg....
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Broken? It was working correctly when I left it.

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Re: PM1 point motors

Postby Ogster » Sat Jul 02, 2016 12:04 am

Splendid idea re the peg - I like it. However, further investigation revealed the microswitch not being conductive at all. Continuity test using the meter showed nothing at all between the common - the frog - and both of the inputs - in my case the DCC. Quick spray with acetone on the motor - used for the cleaning the track - seem to have sorted matters for now. A little odd as the motor is pretty new.

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Re: PM1 point motors

Postby Bufferstop » Sat Jul 02, 2016 10:58 am

Using the copper of a PCB as part of switch contacts can always be a bit suspect, the Peco add on switch suffers the same problem. I think the copper does oxidise but to nowhere near the degree of other metals and not visible to the naked eye. Scratch it, not hard enogh to go through to the laminate, and you'll see the true colour of the copper, for a while. The effect is even more noticeable in aluminium. We had two teachers for chemistry and the junior of the two was up for any experiment with a touch of danger, if it was spectacular enough. He asked what colour we thought aluminium was, we all said grey, he then plunged a bar of ali. into a concoction of strong acids and held it up for us to see, for a few seconds, a silvery colour like mercury. Health and safety would crucify him today!
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Re: PM1 point motors

Postby CandO » Fri Jul 08, 2016 8:44 pm

Sorry for hijacking the thread slightly but are these PM1 point motors suitable for N gauge and if so how big are they? (just the bit under the baseboard) I'm asking cos my layout will be elevated with a 30mm gap between boards....thanks!

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