Garden railroading can be thought of in a theatrical sense. The garden provides the set; the structures the props; and the track the stage. The train is the star of the production and, if the stage has been properly set, the actor must certainly look the part.
Perhaps the first thing that must be considered is the material from which the train is made. Plastic is acceptable (just), but it must be painted to hide the shiny, semi-translucent characteristic that all plastic seems to have. Paint can cover a multitude of sins, including a poor choice of material.
Plastic, though, is not really an honest material. It is as its name suggestsplastic; moldable, able to take any form, and while some may consider this an attribute, I do not. In the garden, the material should be what it appears to be. Plastic is fine for indoor modeling, where the object is realism, but outdoors we deal with reality. Wood (including plywood) and metal should really be the materials of choice for modeling garden-railway equipment.
The trains are large enough that consummate skill is not necessary to build a pleasing model. Id rather see a well proportioned model built of wood and metal with average skill, than a beautifully crafted plastic one. An honest piece of work pretends to be nothing more than it isa working piece of rolling stock for a little railway.
The secret to a pleasing effect in the garden is not in adding as much detail as is humanly possible, but getting the proportions right. The Ten Foot Rule appliesif it looks right from a distance of ten feet, it is right. Good proportions are a must, however. The importance of this cannot be overstated. Well proportioned lumps of wood are more effective in the garden setting than a super-detailed, ill-proportioned model. If you dont believe me, try it.
Painting, as suggested above, is also important, and a good paint job can make up for less-than-top-notch skill in construction. While the airbrush is recommended for small indoor models, a carefully hand-painted model can look just fine outdoors.
Color is critical, particularly on freight trains. Full-size railroads can get away with painting their trains any old color that they find they have a lot of. They, however, are not creating an effect; they are advertising. Bright colors are generally not a good idea for freight cars in the garden. The freight train is the work horse, and should look the part. Use subdued colors, with an occasional bright one thrown in for accent. Be restrained, however, in the use of obtrusive colors.
Artificial weathering is neither necessary nor advised. If you want a car to look weathered, just leave it outdoors over the winter. In the spring you will find that it has been wonderfully aged. If the car was properly constructed, it may even have stayed together.
Passenger trains are another matter, and can be painted more brightly than freight trains. A railroads passenger train is its pride and joy, and should look it. Weathering is a definite taboo for a passenger train, unless it is derelict, in which case see above. Stay away from fancy paint jobs if you cant do them well. While a good paint job can cover a multitude of sins, a poor paint job can ruin an otherwise fine model.
Back to freight trains. Consider the train to be a word. Legibility is the issue here. The train should read as a train (a word), not as a string of individual cars (letters). This can be easily achieved simply by coupling the cars closely. Body-mounted couplers are best.
Also, look at word shapes. In typography, part of a words legibility comes from its shape. Some letters have parts that stick up, some have parts that drop down. Some letters are long and some short. Likewise, a train is composed of cars of different shapes, and these cars can be arranged to create a maximum amount of interest (or boredom, in some cases). Group the cars in an interesting way. Dont stick all the boxcars together, followed by all the gondola cars, followed by all the flats, etc. Thats dullsville. On the other hand, complete randomness is chaos. You must use an artistic eye when building your train.
Some of these rules also apply to passenger trains. They may be thought of as words made of all capital letters, since passenger cars are generally all of the same height. For variety, run cars of different lengths in the same train. Visual continuity (especially important in passenger trains) can be preserved if all cars are painted in the same livery. However, if you are running a mixed bag of passenger cars, the same rules apply as to freight trains. Close coupling is a must here as well. After all, we dont want our passengers dropping between the cars on the way to the diner.
A locomotive should be just thata self-propelled prime mover that carries its power on board. A true locomotive, whether it be steam, internal combustion, battery, or spring driven, has a kind of philosophical purity about it that has great appeal. A track-powered locomotive is dependent upon its track for power. While the following may seem like an obvious statement, let me continue by saying that a track-powered locomotive becomes nothing without its track. It is merely a small part in a larger system, and it must have the rest of that systemthe track, the electricity, the power supply, and the controllerto realize its potential. A true locomotive, however, carries its potential with it, whether it is functioning as intended on the railway, or it is on display in a glass case. It is a thing unto itself, and needs nothing more to make it complete.
Proportion in locomotives again plays an important part in creating a visually successful railway. There are beautiful locomotives and ugly ones. They can be long, short, squat, stubby, fat, thin, tall, massive, delicate, blocky, curvy, and, Im sure, many other things as well. Here again, the artistic eye will triumph. Though a well proportioned piece of rolling stock may be attractive to the eye, the locomotive is the only part of the train that can truly stand alone as a sculptural piece. Because of this, a lot of attention should be paid to its appearance. The engine is the first thing the bystander sees as the train approaches; it leads the train, it is a symbol of power, and it is usually something the railway is proud of. A locomotive deserves to be well proportioned and well finished.
An acquaintance of mine once remarked that a particularly hideous full-size locomotiveone that was cobbled up from spare parts in the railways own shopswould make an interesting model. This was not true. The engine was an offense to the eye in its full-sized incarnation and a model of it would be no less offensive, even though smaller. A model of the engine in question would incline persons of good taste to throw rocks at it, and it would certainly never be a welcome guest on anothers railway.
Consider carefully what engine to model, and even more carefully if you design your own. It is possible to design well proportioned locomotives that incorporate any of the above list of qualities; and it is equally possible to build ugly ones with the same qualities. Be careful.