Wiring and motorising a Marcway crossover

[Irish Padre]

Hello everyone! As part of my new project I have commissioned a 7mm turnout from Marcway. Special build it had to be as it’s to 36.75mm gauge - Irish 5’3”. It’s lovely but whilst trialling it    last night I noticed all kinds of sparks and shorts when a loco with generous back to backs ran through - presumably the blades arcing against the stock rail. Although I was going for the easy option of simply using them as self-isolators with wire in tube operation, I think I need to go for the better solution of using Cobalts with frog switching. I am still a bit away from laying this large piece of track and don’t want to completely remove it from its protective card backing just yet. Can some kind soul please advise me if the frog has a wire already attached (as Peco do for those who wish to add a switch) ? If not, is there a particular place on the frog where I wire it? I understand that I will have to gap the sleepers between the turnout blades, and also gap the blade rails before they hit the frog. Any other gaps required? Thanks for reading thus far!! 

[Barclay]

Hi I didn't respond sooner as I'd hoped that someone with more knowledge than I would know the answer! I've never used a Marcway point but have built a lot of copperclad track in my time.

 

Normally I would expect to see an insulation gap in the point blades perhaps 4 or 5 sleepers from the crossing, or frog. Up to that sleeper, going from the blade end, each point blade will always be the same polarity as the adjacent stock rail, so insulation gaps are required in the sleepers in between the blades. After that point, running up to and through the crossing, that whole assembly can be treated as a single electrical unit, the polarity of which is switched as the blades are thrown, so insulation gaps are needed in the sleepers between this unit and the adjacent stock rails from that point. Finally, there should be gaps between the 2 points, as a crossing should never be fed from the 'tail' end.

 

I hope that helps but would point you to Iain Rice's track construction book for some excellent diagrams and explanations of how to wire even the most complex trackwork.

 

By the way, if you are using wire in tube, try using a double throw slider switch as your point lever. You can use the electrical contacts to create a 100% reliable switched feed to the crossing of the point.

Edited October 21, 2019 by Barclay

[hayfield]

Am I correct in seeing an isolation gap in the curved stock rails just before the extended check rail

 

Also are the isolation gaps in the sleepers between the stock and switch rails and the common crossings are energised when the switch blades touch the stock rails ?

[Ray H]

The few Marcway points that I have seen have been built so no frog switching is necessary. They seem to rely on the back of the blade always making an electrical contact with the stock rail. I've invariably converted them to the more conventional (?) method of working without relying on the back of the blade contact which will ultimately fail in numerous installations.

 

The way the crossover appears to have been wired there looks to be every chance that tender loco wired the American way - the loco and tender are live on opposite axle sides - will cause problems because the rail breaks in the curved stock rails aren't opposite each other. We've had this kind of problem on the club layout.

[Irish Padre]

Apologies everyone / just seen your answers! Ended up slicing gaps into the point and wiring it properly, with switched frogs. In process of bedding it in to layout now with DAS clay as ash ballast. Thanks for your advice which, as it turns out, I have essentially followed! 

D

Edited December 28, 2019 by Irish Padre