There are a whole lot of reasons why a three axle chassis with one end axle fixed is a bad idea. If you compare a fixed end axle plus a single beam for the other two with a rocking end axle plus two side beams for the other two, you will see how poor its stability can be. Just draw the triangles connecting the three suspension points for each case.....
I am confused here Andrew. Are you saying it is
the fixed axle chassis that has poor stability compared with one where no axle is fixed?
My general point in the article was that regardless of whether there is a fixed axle or not it is the pair of axles that need to be biased to the outer axle. And that the tender thing of Allan's suggests he found the same.
Your restatement of your first post into two points enabled me finally to understand it! However
much I agree with all the issues you mention that need to be right, though, the fact is that my locos
etc manage not to derail on what may be all sorts of minor track faults where some other stock can and sometimes does derail. So perhaps this uneven weighting can be regarded as a bodge to
overcome track bodges. Anyway I see no downside to it at all. Inner wheels that may be weighted at 50% show no tendency to derail and
the instances where they did I covered in the
For instance on the club layout there is a 4ft radius approx curve that catches some stock out, but I regard mine as a failure if it fails to negotiate it, and I remedy it. Currently I am trying to remedy the
curve to be less troublesome by increasing the GW from what the triangular gauge gives, to 0.2mm, and putting in a (very) little cant. Time will tell if that is sufficient answer to the problem. Next would be adding a checkrail. But I suspect the issue may be there is insufficient transition. I attach a drivers eye view hopefully.
I quite concur that I am nothing like such a refined modeller as you and others. I have no qualms in doing whatever cheating is necessary if it achieves my objective, zero derailments, and I do
claim to achieve that, by and large.
By the way the business about yaw stiffness I also mentioned ( though without knowing the proper terminology) and showed my Comet bogies that
rotate on small wheels. I wonder what your remedy was and how the problem arose?
Please excuse my possible lack of nuance in this post Andrew. Still on mobile phone.