I started a topic on 2ft gauge miniature railways recently ( http://www.009society.com/forum/index.php?topic=942.0 ). Often these use steam outline locos, and I wondered how you could model these and distinguish them from steam locos, given that our models are electrically powered anyway. The only solution I have thought of so far is to model one of the hopelessly unconvincing ones that are basically just a Simplex with a wooden body, which is not really what I had in mind.
I think that is always going to be a problem, particularly if you include actual steam locomotives that have been converted to infernal combustion as I believe is the case with one Japanese tourist line. Any simplification of the motion or other detail is going to be indistinguishable from a model of an actual steam locomotive that is not built to rivet counting standards.
If you can show the controls in the cab that might be one way perhaps?
There is a WW1 WD Hunslet 4-6-0 that has a diesel engine fitted in the boiler as well as a Hudswell Clark 0-6-0 tender loco with a diesel engine in the tender and no doubt others that look just like the originals but are now actually IC powered locos. Then there are some very convincing steam outline locos like the ones built by Alan Keef for the, the Lartigue Monorail at Listowel, County Kerry.
I have also seen many freelance 009 locos built on N gauge chassis that unintentionally look like bad steam outline diesel powered locos!
So yes it is not an easy thing to replicate in 009.
Brian Meldon
Sadly this would not work for the Severn Lamb locos that I was thinking of, which are built as i/c locos from new, are quite convincingly steam-like, and have transmission by coupling rods.