Six-wide vs eight-wide
There is a long running debate (often seen as a joke) about the merits of various train scales using the LEGO track gauge and couplers/wheels etc. The 6 or 8 refer to the basic body width (in studs), although many models have protrusions that take the width a bit beyond that. This post on LUGNET shows one of the more heated arguments regarding scale.
Each width presents fans with a number of advantages, with the advantages of one width often being seen as the disadvantages of the oterh.
6 wide advantages
- Consistent with (most) LEGO sets in rough scale and proportion (Town sets have traditionally been built to varying scales; something is more compressed the larger it is, so there is no one scale)
- Use fewer parts than 8 wide.
- Less overhang on tight radius curves than 8 wide
- Often more challenging to build 'to scale' than 8 wide
- The model is often stronger using the standard train base even when lengthened to fit the scale length
- Building a train roof is simpler using standard parts.
8 wide advantages
- Closer to scale with minifigs and trucks
- Trains are generally more solid, and tend to look more imposing
- Allows for more detail as there is more space to work with
- The width better allows more realistic running gear - including drivers, connecting rods, valve gear, oustide freams and brakes - within the width of the piece of rolling stock
Loading gauge (the allowable dimensions of railroad equipment) varies from country to country in reality. Broadly speaking British trains are small, European are medium-size, American are large and Russian are huge.
Lego trains are shortened even in proportion to their width; at any width, fans may or may not do this. Sometimes, 6-wide six-axle diesels and electrics end up overly long relative to their width; this is forced by some types of truck design.
There are other choices of scale; 7-wide, 9-wide and 10-wide have been used. These are covered in trains of other scales.