I'd have thought that the first thing you need when designing a model railroad is a pretty thorough knowledge of your chosen prototype or if you have no specific prototype, at least some knowledge of general railroad practise, and that means looking at the real thing and not at other modellers versions of it. Once you have that, then your design work is essentially one of interpretation. I like xtrkcad but it's not where I start with when thinking about a design since it is too easy to keep cramming in track and to forget about what the rr will actually look like.  
If I was you, I'd get paper and a pencil but leave aside the ruler and compass for now. Thing is, whenever we design a layout we automatically do it in plan view but truth is that is the one view none of us will ever have of our layouts, unless it's in the garden and you hire a helicopter!
What you will see on the finished layout are the side on views across the tracks so you might first decide do you want a direct side on view, as though standing next to the tracks on the real thing, or an elevated view, as though you were on a crane looking down at everything. This will tell you how high the benching will be and in turn that will suggest how far any tracks can be from the edge of the layout and still be reachable. Then you can think about the views up and down the line and think about the buildings and the scenery and how you might use them as viewblocks so you don't see all the railroad at once and hide those bits where your rr surveyor, for no good reason, executed a sharp 90 degree left. As you do this, you'll find ideas that you like, little scenes or arrangements of buildings, scenery and tracks and you can begin to sketch out some plan views to knit all these scenes together.

Only then need you turn to xtrkcad or whatever and plan everything in detail.

Aha. Thanks Roand. Intriguing. From a quick google, it seems the Lackawana and Western also went in for camel backs so perhaps the steel company got the idea from them. Admittedly, the 0-4-0 looks like someone sneezed when 'glueing' the cab on, but the 0-8-0 looks a fair match for the camelback mogul.

The Torch lake camelback doesn't really count imho as 4'1" is scarcely 'narrow gauge'

True, but I want the restriction of staying close to prototype practise!

I had found the shay/kitson meyer and I could see it  made sense to 'just' jack the shay up and replace the trucks with the steam bogies and plumb in new steam and exhaust pipes (though I did wonder how they counterbalanced the shay's offset boiler).

But a shay into a pacific is plain weird. At what point does a shay rebuilt into a pacific become a pacific rebuilt with a shay boiler? Also, where on earth does the shay's firebox/ashpan go?

Aha. Thanks Ken. So there were two 2 cyclinder, 3 truck T boiler shays and, reading the note, only two, 2 cyclinder 3 truck shays built.

Well, that's 2 more prototypes than a narrow gauge camelback (I think) and two more than the 2-4-4-2 mallet!

BWM are clever blighters but I do wonder if there were any 3 truck T boiler shays. The last T boiler was 1891 and the first 3 truck shay 1885 so there is a 6 year overlap but a brief search on google has found nothing and http://shaylocomotives.com is none too search friendly.

Mind you, I couldn't find any 30" camelbacks either

You could take a look at this. Has some good pictures of a detailed cab.
http://1stclass.mylargescale.com/mikereilley/Engine%20bashing/Jack%20Thompson%20C20%20Super%20Connie.pdf

Nice link, Kevin. The 2-4-0 especially is ridiculously cute and not disimilar from some Bachmann Forney bashes.

Bachmann's o/s frame 4-4-0, the connie and both mallets would look rather more at home on this kind of RR than they do on model RRs set in the US.

Aha. Thanks Hamish. I figured that must be the case.

If it was a Baldwin catalogue product but there are no known prototypes* does that mean Baldwin came up with a design but got no takers for it?

*That NZ Alco is similar but apart from being wrong gauge and wrong manufacturer it's a compound with a tapered boiler. I'm not complaining that there is no 'physical' prototype for the 2-4-4-2, since the fact that it is not specific to any one RR actually increases the options of using it.

Given that Kevin has identified the 2-6-6-2 as being built for a line with a very low axle loading it would be interesting to compare the axle loading on the 2-4-4-2 and see if they're similar.

That question has been asked on several other forums and to date I haven't found anyone come up with an answer. The assumption seems to be that it is in the style of Baldwin but basically freelance.

Quote from: Royce Wilson on September 11, 2012, 04:55:50 PM
Check this old time 4-4-0 out!

Beautiful. I recommend viewing that image full size. You can nearly read the builder's plate.
Well, maybe a slight exageration, but you can read the builder's plate on the smokebox door.

And for those after 'eastern' prototypes, does it get more 'eastern' than Florida?

edit: more on the Jupiter & Lake Worth. Seems like a fascinating little RR: http://www.taplines.net/jalw/jalwry.htm

Interesting to look at the size difference between the loco and the passenger car.

Given that Bachmann's three truck shay is a development of their earlier two truck shay, I suggest you look on the second hand market.
The two-truck shay is out of production (I believe) but you can see what it looked like here: http://www.btcomm.com/trains/primer/whyscale/bachshaymini.jpg

I think the lure of the 1:20.3 4-4-0 and 2-6-0 for the On30 brigade is down to the different nature of smaller scale and large scale modelling. In the smaller scale there is usually more of an attempt to model a 'railroad', be it a prototype or a fictional interpretation while in large scale it's more about running the trains you like without intending to create a specific railroad with a backstory (Tuscarora is a great exception).

Hence, while the largescale railroader will tend to buy a loco because he likes it, those in the smaller scale trying to create a particular railroad will tend to want the appropriate stock to operate it and the key thing about the largescale 2-6-0 and 4-4-0 is that while they were found everywhere (even central/Latin America as I discovered yesterday) there were many railroads that - at least for a period in their history - ran little else. This is especially so west of the Rockies where the rosters of railroads like the E&P, Nevada Central, N.C.O, Truckee-Lake Tahoe and the coast railroads in California were dominated by them. Indeed, just as it is 'impossible' to model a decent logging RR without a few geared locos, it is impossible to model a Nevada, Utah or Californian common carrier without a handful of 4-4-0s and 2-6-0s. Thus, models of these two engines will not only fit on most modellers' existing railroads they will open up new areas of modeling that have previously only been possible with expensive brass.

The Eureka http://en.wikipedia.org/wiki/Eureka_Locomotive was built in 1875 and worked on the Eureka & Palisades until 1896 when it was sold to a lumber company. It was still working in 1938 when the company folded.

Working life 63 years.

Sonoma, more or less the same design, was built in 1876 for the North Pacific Coast, and sold to the Nevada Central 3 years later. It was still in servive in 1938 when that line went under.
Working life 62 years.

Jupiter, same design again, was built in 1876 for the Santa Cruz RR but was sold in 1881 when the line standard gauged and went to Guatamala where it was still working in 1960 http://americanhistory.si.edu/collections/locomove/locojh.htm
Working life 84 years!

All three locos are still with us.

This might be useful: http://www.pacificng.com/ref/blw/818C/8-18C.htm it purports to be a Master list of Baldwin 3' gauge gauge 4-4-0 locomotives and includes scrap/disposal dates. many had working lives of 40 years or more which is not bad for engines only of limited era use.
In fact, in terms of usefulness, a Baldin 8-18c has far more to offer than any D&RG K series.

Of course, many of these locos would have changed their appearance over the years with new stacks, domes, cabs and so on but that's what modelling is all about.