The simple thing, which is close enough for model RR work, is this:  1" in 24" = 4%; 1" in 36" = 3%; 1" in 48" = 2%.  These are close approximations, but we're not doing prototype engineering where each half a percent has significant effect on how much train you can pull.

There are brass detail parts available for items such as brake cylinders and generators.  See the Cal-Scale line from Bowser, and PIA parts from Precision Scale, among others.

Did you perchance happen to turn one of the tender trucks around?  That would do it.

Steam locomotives were the "space shuttles" of the mid-19th century, and were generally treated as such.  It was partly Victorian style, partly pride of ownership, and partly pride of craftsmanship that resulted in the various colorful schemes.  This practice lasted into the last quarter of the 1800's, but began fading as railroads consolidated, became more uniform in their practices, and looked to economize by not spending money on the labor needed to apply and maintain the more elaborate finishes. Black was sort of the default finish becuase it was durable and compatible with the black cinders they rained down on the equipment. The use of "Russia Iron"  appears to have lasted into the early 20th century with some roads.  Vestiges of special decoration lasted almost to the end of steam - witness the striping patterns on the Pennsylvania RR's passenger locos, the Southern Railway's apple green locos, and the B&O's President class Pacifics.  The finishes you see today on locos such as the Golden Spike replicas, the narrow-gauge "Eureka", and the "York" at the Steaming into History operation near York, PA are pretty accurate to the time and place they represent. 

Here is one good source:  http://www.pacificng.com/template.php?page=/ref/color/index.php

I was there two weekends ago, for the first time in many years.  IIRC, No. 11 was working the Whitaker train, and we had the Pacific Coast engine on our Bald Knob run.  First visit, the old shops were still standing, along with about half the mill.  I rented WM 6 and a photo freight back in 1982 and ran all the way to Durbin and back.  Cost? $850.00!  The new D&GV management hopes to have the Durbin line back in 2019, and maybe both Climaxes.  Right now, Heisler 6 is working the "Durbin Rocket" while the Climax is undergoing her 1,472 work.  Note that B&O modeler/expert Bruce Eliot is building a very large B&O display layout in Greenbank and visitors are welcome.  Google him for details. 

Mr. Bachmann - Some inspiration?

https://www.youtube.com/watch?v=7ec9HtqfdgU

Compounding for steam locos means using the steam twice before exhausing it.  After being used one in a cylinder stroke the steam still have a lot of energy left, but at a lower effective pressure.  It can be routed to another cylinder that has a larger diameter than the initial (high pressure) cylinder to compensate for the lower pressure.  If you look at pics of early articulateds, the front cylinders are much larger than the rear for this reason.  Using the steam twice increases the efficiency of the loco, resulting in better water and fuel usage.  With standard non-articulateds, there were two common methods of compounding - Cross compounds, where the cylinder on one side is larger than the other side; a Vauclain compound (named for the president of Baldwin in the turn of the century period) where on first look the cylinders look like they have two valves, when in fact one of them is the high pressure cylinder.  The development of the superheater spelled the end for most compounds, since the efficiency was achieved without all the extra machinery. 

Three-cylinder locos were developed in the 1920's mostly to give some extra boost.  They were not compounds - all cylinders received high-pressure steam.  They weren't overly popular in the U.S., probably more so in Europe.  The Southern Pacific had a fleet of 4-10-2 three-cylilnder locos.  The U.P.'s fleet of 4-12-2's were originally three-cylinder machines.  The third cylinder and valve were buried in the middle of the cylinder saddle.  The give-away was the Gresley valve gear mounted on the pilot deck.  The Baldwin 60,000 4-10-2 on display at the Franklin Institute in Phildadelphia is a three-cylinder loco.

I've mentioned before a desire for a non-Rocky Mountains Consol, like the Lawndale 2-8-0's.  It is small and pretty generic, making it suitable for bashing into similar prototypes.

Dave:  Your "non-0-6-0" would lead to the Consolidation - these engines were the "maids of all work" during the steam era.  The Bachmann loco is a typical 1920's era loco that would last until the end of steam.  Consols were the primary freight power from the 1870's until the early 20th Century when the Mikados and other trailing truck locos came to prominence.  The last steam loco in regular service in the U.S. was a 2-8-0, running into the 1980's.

IIRC, the stillborn B&O 4-8-4 was intended to utilize some form of Vee-engine design, with a two-cylinder Vee engine hooked up to each driver axle.  I think Mt. Clare actually got some work started before management decided that diesels were the better deal. 

You can get travel power converters that drop the voltage from 220 to 110.  I've used one on my overseas trips.  They should be sufficient to power a trainset power pack. 

I was going to chime in too - the photos didn't come through, just some banner about needing to update Photobucket.

Yes, there is quite often a difference between "official" designations and operations parlance.  Among head-end people, use of the number reference was more accurate terminology because everyone knew exactly what was meant.  "Those 2100's couldn't get traction in a sand house, but those 2400's would pull everything out of the yard".  That sort of thing.  As for the PRR, they had a big habit of spreading loco numbers all over the place with no reference to class or type of loco. 

OK, some more on steam locos.  The various wheel arrangements were given generic names to help sort them out for folks who didn't know all the various classifcations of the different roads.  Sone of these names were often tied to the road that first ordered a particular type - The Consolidation (2-8-0) name came from the 1860's when several railroads consolidated into the Lehigh Valley and ordered that new wheel arrangement.  Atlantics (4-4-2) were named after the Atlantic City RR;  Pacifics came from the Missouri Pacific.  Here's a partial list of some of the more common types:

4-4-0 - American
4-6-0 - Ten-Wheeler
2-6-0 - Mogul
2-8-0 - Consolidation
2-8-2 - Mikado
4-4-2 - Atlantic
4-6-2 - Pacific
4-8-2 - Mountain
4-8-4 - Northern (or Niagra, Pocono, Greenbrier, Dixie, etc.  Long story about these various names)