Garden Railway Forum

It seems that in descriptions of various locomotives, different size designations are used at different times. It is difficult to compare apples to apples. The fact that inch and metric are used does not help the situation. My general interest is with units that can operate on 45 mm track, but I would like to figure the entire system out. Thanks for any assistance. Jim

I think this topic is best described as a can of worms ......

I'll take a first stab at it, but no doubt others will chip in and maybe even contradict what I say. But here goes.

45mm (or 1¾") gauge was originally devised for standard gauge models and called Gauge 1. The scales varied across the Atlantic between 1:29 and 1:32.

However, 45mm gauge has now been used for narrow gauge models and so the scale depends on the gauge being represented. So,

• Metre gauge models on 45mm track = 1:22.5

• 3 foot gauge on 45mm track = 1:20.3 or F scale or 15mm : 1 ft

• 2 ft gauge on 45mm track = 1:13.7 or 7/8" scale or SE scale

• Approx 2'9" gauge on 45mm track = 1:19 or 16mm : 1 ft scale or SM45

To complicate things, G Scale or G Gauge is often used by manufacturers to refer to almost any of the above

I hope that helps in some way

Rik

^^^^^^^^^
Exactly what Rik said. Well done Rik, great explanation

Thanks. It was very helpful.

I find these helpful...

G scale and G gauge was the one that confused me at the start, by right every scale should be using its own gauge which is in fact also the correct scale, but many scales "borrow" a gauge to simplify things, and scales have developed because of the track sizes available.
No one intentionally decides to model in 1:20.3 scale they would select 1:20 much easier than using .0492341 in your calculations, but if you want to use 45mm off the shelf track and model in true scale then for 3ft narrow gauge thats your scale.
Personally I dont like larger models using a smaller gauge they always look like they are about to fall over. would be more in favour of going next gauge up than down, but personal opinion.
And as mentioned the mixing of imperial and metric really does add to the confusion, any wonder its always the "what is the difference between" first question of people coming into the hobby

SeamusOD wrote: Mon Jul 20, 2020 1:34 pm ... by right every scale should be using its own gauge which is in fact also the correct scale, but many scales "borrow" a gauge to simplify things, and scales have developed because of the track sizes available.

I think you mean that every scale "should" use a specific gauge for a *given* gauge being modelled. One point of confusion - at least when trying to explain things - is the simple fact that we are modelling narrow gauge, whereas the standard scale/gauge combinations (00, HO, N or whatever) assume standard gauge.
The borrowing of gauges arises from convenience of using established supplies (the classic example being the 00 use of 16.5mm for 1:76 scale in order for the electric motors then available to fit inside smaller British prototypes - the constraint no longer applies but it would be so difficult to change over to 1:87 British outline that it has never been done commercially and those chasing accuracy increase the gauge rather than changing the scale).

TonyW wrote: Tue Jul 14, 2020 9:57 am I find these helpful...

That's really good. Is there an equivalent for 32mm gauge, preferably including 16mm scale?

yellow_cad wrote: Mon Jul 13, 2020 8:29 pm The fact that inch and metric are used does not help the situation.

Do you mean the "X millimetres to one foot" thing? I think that's a uniquely British way of talking about scale - elsewhere the rather more obvious "1:XX" format is usually used.

CSL wrote: Sun Aug 09, 2020 10:14 amThat's really good. Is there an equivalent for 32mm gauge, preferably including 16mm scale?

See viewtopic.php?t=8024