Since the beginning of model trains, 0 gauge model railways have been a popular choice, especially in the UK. The 0 gauge is a ratio of 1:43.5 or 7mm to the foot. The prototype that you may run can be standard, broad, or any of the narrow gauges for 0 gauge model railways. Here is an overview of the different gauges within 0 gauge railways.
Standard gauge and their popularity:
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Standard gauge has been the most popular gauge among 0 gauge modelers and still holds strong today. The main reason for using 0 gauge is to have fun and have models that aren't completely realistic but have speeds and incorporate turns that wouldn't really be possible in real life. Since these models have unrealistic speeds and turns, it led to the adoption of new track dimensions with deep wheel flanges and wide treads and locomotives began to have over-sized wheels. The relatively easy assembly and construction of these models is what made them so popular. As modelers have worked with the gauge more, there has been a shift from unrealistic to more realistic scales.
• Coarse Standard - contains deeper flange and wider treads. This will ensure that the wheels of a locomotive can tolerate a bad track. The track in coarse standard is compatible with most 32mm gauge wheel sets. You can find used models for very low prices which is very beneficial for new and older modelers. The disadvantages to using coarse standard, is that the track work crossing dimensions are over scale. The wheels back to back are less than scale which can cause altered dimensions for your locomotives and their frames. The body of your trains may seem distorted.
• Fine Standard - the most commonly used standard in 0 gauge model railways. This standard is a hybrid between appearance and the easy ability to use and set up. Fine standard brings the outer face of standard wheel sets closer to scale so that appearance looks more realistic. Since the clearance between wheel flanges and the rails is greater than scale, locomotives will be able to run around curves at much sharper angles than scale. Ready to run models almost always use find standard wheel sets. The disadvantage to fine standard is that the crossing dimension is over scale because of the increased clearances, which some modelers believe that it gives the model a strange appearance.
Broad gauge within 0 gauge:
Broad gauge models can all be done by using components of the standard systems above. The wheel and track dimensions stay the same except those based on the track gauge which must be increased to fit the prototype. Broad gauge is less common so there is only a limited amount of commercial items available on the market.
Narrow gauge:
The two groups of modelers who use narrow gauge can be split into two groups. Those who use existing track systems like 00, N, and Z gauge and those who would rather model the exact track gauge and build their own track work. You can determine which category you fall under if you choose to do a narrow gauge. Both options will allow you to use components from 7mm scale such as buildings, figurines, and other scenic details and landscaping components.
With O gauge trains there are plenty of options as you can tell. It is all based on the shift from unrealistic to more realistic models because 0 gauge originally began as a strange scaled model that were used mostly for toys. Now you can take your pick in 0 gauge model railways and even tailor your own railway to what gauge size and scaling you really want.