I’ve spent a couple of days now puzzling over a derailment at the south end of the siding. The gauge is fine, almost too wide, and there is only the tiniest unevenness to the track.
Then I got the phone out and shot a video on the far side, and the problem was immediately apparent. The heal of the switch admits a tiny step down, and it’s just big enough that the front truck of the tender isn’t able to find the rail head.
The step is only .19 mm (.008”), but of course the flanges are only .31mm, and you can see the wheel ride up onto the rail head briefly before falling off the wrong side.
Fixing derailments is a little like fixing bugs in software: once you know what’s causing it, it’s usually straightforward to resolve. Video is a superb tool to find the cause.
Pembroke:87 