I've recently spent some time (figuratively) crawling around under coal wagons inspecting their braking systems, in order to try and design a simple, but accurate, representation that I can add to my 3D printed underframe. One of the things I've discovered (two excellent resources are here and here) is that while the brakes on my model coal wagon worked so well that the wheels wouldn't turn, in real life they wouldn't have worked at all, as I fitted them the wrong way around.
Not only did I manage to fit the brake system wrong on the Parkside Dundas kits I built, but it appears that I'm in good company as neither Dapol or Hornby seem to model fully correct brake gear either.
So which version am I going to add to my 3D model? Well given that there will be no difference in cost, if I can work out a sensible way of modelling the clutch, then I'll probably model all three correct versions. This way I can print which ever I want depending on what time period I want them to represent. This is one of the main advantages of 3D printing over traditional manufacturing; there are no upfront cost to create expensive moulds, which allow us to print variations at no extra cost.