Fixed Pony Truck on Duchess causing issue at points

[ColinB]

This is for general information, I have fixed the issue, but I thought it might be useful for others to know. I came up with what I thought was a clever way to drive a relay on a point from the DCC signal, I did do a post about it. Anyway I attach wires to the non moving part of the blade and the opposite rail to drive a relay through an AC to DC circuit. It worked perfectly with all my locos except this Duchess. On this one point on my layout the loco would stop and the controller trip out. Eventually after a lot of testing I found that the dummy pony truck wheel was dropping onto the non used part of the blade. The wheel is just wide enough to short the unused blade and the rail it would connect to, if the point was switched. So my circuit thought the point had switched, so changed the polarity of the frog and hey presto we have a short. I did initially change the pony truck wheel to one off a Britannia which is smaller and this cured the problem, but I figured that eventually another loco with a similar pony truck would do the same. In the end I decided to use an autofrog circuit which cures the problem and just use the relay for enabling the isolating rail before the point. That probably also explains why on the W1 the pony truck wheels are miles away from touching the track, although Hornby don't use a circuit like mine, I assume they found it caused other issues. Of course with all my locos that have a normal moving pony truck there isn't a problem, which is why when I tested it on my other locos I never noticed it.

[RB51]

That’s great Colin. Thanks for posting. R-