Keith,

First and foremost, you need to have a look at some drawings for the prototype, also keep in mind a lot of purpose built for 2ft. gauge loco’s had the outer face of the wheels running about 3/4”-1” away from the inside face of the frame, it would be almost impossible to replicate this in model form because you would quickly have electrical shorts happening,

Some loco’s like Fowlers were built to allow the loco to be used for a variety of gauges such as the Resilient Fowler Peldon at Amberley in the UK, this type of loco has the frames set at 985mm, OD, and could be set to run on 2ft. gauge or up to 2’6” gauge, the 2ft. gauge version of the 0-4-0 Fowler like Ixion released last year has the frames set at 3’11” ID, again it could be used on 2ft. gauge or up to 2’6” gauge.

See etched model [1/35th scale Fowler DM]

As a general rule of thumb when designing a etch layout for frames I try to allow a minimum of 1mm. from the outside face of the wheels to the inside face of the frames, and that’s allowing for about .5mm. side play of the wheels, however you need to also look at what has to go on the outside of the frames, ie: fly cranks rods etc. and how thick/wide are they going to be in relation to the overall width of the loco.

If you want any help or advice on how to set out the artwork, feel free to ask.

?

Brian
Qld. Aust.