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New Member
Hi Guys,

Please forgive my ignorance, but I thought I understood the collective jargon that is applied to the various scales and their narrow gauge derivatives.

But can anyone explain to me the difference between On3 and On30?

(What a time of life to be getting into O scale..........)

Thank You



Railroad Photographer
The difference between On3 and On30 is 6 scale inches. Most prototype railroads in the US were 3 foot gauge (as in On3). On3 has been a minor scale in our hobby for a long time, and as a result, most of the engines are fairly expensive brass ones. This has kept many interested modelers out of the hobby. On30 has been around for a while, modelers using HO scale track because it works out to 30" in O scale. They used HO scale power mechanisms under scratchbuilt bodies.

Bachmann came out with On30 trains ten years ago, and have been releasing very high quality and affordable equipment ever since. This has caused a growth in On30, with other manufacturers bringing out rolling stock too.

In some cases Bachmann's On30 power is about the same price as similar Ho scale models -their Shays are around $125.00 or less. Try finding an On3 one for ten times that much!


New Member
O Scale Narrow gauge

Hey, Thanks Bob,

So, On3 equals 36" or three foot gauge, and On30 equals 30" or 2' 6" gauge.

That (sort of) makes sense.

The reason I ask is that I have always been in love with small tank locomotives (as well as Shay, Heisler, and Climax geared locos). Recently I have had the chance to access some secondhand On30 bits and pieces, and I have always admired the amount of detail that O scale affords, as opposed to my (45 year old) love affair with HO.

While I will not tear down my HO layout, (nor would I wish to) I can see a small On30 branchline down one side of the garage, with possibly a logging or mining theme......

Now, where did I put that spare 16.5mm track....

Many thanks.


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