Marcway pointwork query

[ClaretChris10]

I have invested in the excellent Marcway turnouts, I'd like any tips on wiring. Do I need to make the frog live ? A wiring diagram would be most helpful. 

[Barclay]

On 11/09/2021 at 17:01, ClaretChris10 said:

I have invested in the excellent Marcway turnouts, I'd like any tips on wiring. Do I need to make the frog live ? A wiring diagram would be most helpful. 

Seeing as no-one has responded I will have a stab at answering. I have never used a Marcway point but believe they are constructed on copperclad strip in the same way as the old SMP point kits which I think Marcway still sell(?) and I have built many of these.

 

Each point blade should be electrically bonded to its adjacent stock rail, which is probably done automatically because of the conductive sleepers. As each point blade curves towards the frog there is likely to be a rail break which insulates the blade from the frog and its adjacent knuckle rails and check rails. This is because that entire assembly needs to be switchable to either polarity depending on which way the point is set. It thus needs a switching system of some kind. I remember the SMP point kits coming with a tie bar that had delicate rubbing contacts to achieve this - I wouldn't consider that to be reliable and would recommend you switch the polarity of the frog with a switch on the point motor, or a microswitch activated by same, or by a separate slider switch which can also be used to operate a physical wire in tube or rod type operation of the point. The rails immediately after the frog need to be isolated from the next section of track as a live frog shouldn't be fed from its 'tail end' in case of short circuit.

[Ray H]

Marcway have their own way of arranging the "wiring" of their points. It relies heavily on the point blade making (electrical) contact with the stock rail as this avoids any need to switch frog polarity.

 

Personally I've always modified the points by adding further cuts in the copper surface so that they don't rely solely on that physical contact. I think I've also bridged some of the cuts Marcway put in and (although I can't swear to it as it's a while since I did one) I also cut what are effectively the closure rails to totally isolate the frog.)

[brossard]

I have never liked the idea of relying on electrical contact between the point blade and stock rail.  In my experience this doesn't end well.

 

I would point to the wiring diagrams here:

 

https://www.wiringfordcc.com/switches.htm

 

Crossing (or Frog) Polarity can be changed in several ways.  My preference has been to use slow motion motors such as Tortoise or Cobalt.  I have built numerous turnouts in 00 and 0.

 

John