The Steam Shoppe

Possibly the first step towards a model train purchase is to decide which size would best suit you.  We're going to discuss a little about Scales and Gauges in hopes to assist you.  What does it mean when terms like HO Gauge, N Scale G Scale are used when referencing model trains?  

First the two terms Scale and Gauge.  Scale is just that, a scaled down version of the real thing.  Gauge is actually the distance when measuring between the rails of the tracks.  The standard real-life train tracks measure 4' 8 1/2" between the rails.  It is possible to see more than one Scale train that can run on one Gauge track, but we're going to try and keep things very simple.  In fact, we at http://www.thesteamshoppe.com/store/207/category/70# use the terms interchangeably.  Hopefully that isn't more confusing!

Now lets look into the divisions or ratios of Scale and Gauge as illustrated in the image.  The G ratio is 1:22.  That's a model scaled down 22 times from the real-life standard.  This ratio roughly equates to 1 foot to a little over 1/2". The model track would measure about 1 3/4" between the rails.  G is known as the Garden Gauge because it's quite large.  How large?  Not very clear yet, is it?  A G gauge track has a minimum diameter of about 4' 4".  The diameter is the distance from center to center of the track when measuring a full circle, so the overall minimum width could be 4 1/2 feet depending upon the style of track.  Keep in mind that individual locomotives have a minimum turning radius depending on how long the locomotive is.  Let's list all of the ratios in a table:


         Minimum
Model     Diameter     Ratio      Scale                     Gauge
G         4' 4"        1:22       1ft = ~.55" (14 mm)       ~1 3/4" (45 mm)
O         31"          1:43.5     1ft = ~.28" (7 mm)        ~1 1/4" (32 mm)
S         40"          1:64       1ft = 3/16" (~5 mm)       ~7/8" (21 mm)
HO        30"          1:87.1     1ft = ~.14" (3.5 mm)      ~5/8" (16.5 mm)
N         17"          1:148      1ft = ~.08" (2 mm)        ~3/8" (9 mm)
Z         11.4"        1:220      1ft = ~.06" (1.4 mm)      ~1/4" (6 mm)

Notice the HO Ratio is about half of the O Ratio?  That's how it got it's name, Half - O.

If you'd like to start by buying a complete train set, they usually give the dimensions on the packaging.  If you'd like to design and build your own, the above chart can be used as a starting point in determining how much room a scaled model railroad will take up.