Rev Awdrey famously called his GWR 060 pannier tank engine 'Duck' because the model he had waddled, possibly due to a poorly built chassis, but real steam loco do waddle when they start running.
Anyway I noticed one of my new locos waddling when i tested it last week, and that was running on a Bachmann USRA 060 chassis with main rods from cylinders connected to rear wheel. As I have been looking for chassis for the locos I am building I notice that many 060s have the middle wheel connected to the cylinders and wondered why.
Obviously connecting rods need to be as short as possible, but which wheel is preferable, is the rear wheel better because there is maybe more weight on that axle, or the middle one because maybe it reduces waddle.
Checked out the Heywood book and the 060 locos all have the middle axle connected to the cylinders. Maybe this helps flexibility on sharp curves.
Many of these locos are also outside framed, but I am not even going to atrtempt that, but do want the feel of the loco to be right, so am at least trying to get connecting rods looking close to original, but probably still wrong for the purist.
With freelance locos we are the designer but still need to make things look plausible.
So which is better middle axle or rear axle?
Narrow gauge Francophile interested in 1m, 60cm,50cm , 40cm and smaller gauges . Build in scales from 1/6th to 1/24th. Also 1/32nd and 1/35th using 16.5mm track to represent 50cm and 60cm gauges. http://www.rue-d-etropal.com