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Are there any Standards for On42 ( 1:48, 3ft.6in. COLONIAL gauge?)

I am looking at a Steam era,

1940s-early 1950s Queensland Government Railways steam diorama layout, of necessity fully scratch built...some period freight cars are available ( urethane) as are some Bogies and car wheels, but that's about it.

Locos are similar to US 3ft examples, in fact 1880s QGR used some Baldwins;( 4-4-0 , 2-8-0, ) and WWII NG USTC 2-8-2.

I will be looking for Loco wheel sets, add-on parts, etc. for Brass/styrene Engines, and Wood/Brass for Rolling stock.

Relevant Designs are available from Our excellent State  Railway Museum Archives, including most items from 1865 to 1960s...( Steam era) and some standard structures as well as track standards. I already have experience in HO, and Sn42 building, ( wooden & metal), but with increasing age, weakening eyesight, and fumble fingers, would like to try a bigger, more realistic scale.

I would appreciate any help from US and Aussie modellers with On3, On2 or On42 or On30 experience in scratch building techniques and loco building.


Doc AV



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HO guage track is actually 32 inches or so.    Howver, the Bachman steamers are models of pretty small prototypes which probably would not see service on a big main line.   

It sounds like a lot of kitbashing.    But as mentiioned above, it S gauge track is about right, that may make it a much easier to build steamers to this this gauge.      You coudl use a lot of existing mechanism and just change cabs and maybe some other details.

Thanks for the replies. With further research, Bachmann On30 range of locomotives, 4-4-0, 2-6-0 and 4-6-0 Baldwins closely match the QGR classes A10 (Bald.), B11(Bald.), and B13 ) Baldwin--- all 1877-1890 era engins...scrapped in 1920s-30s.

By rebuilding the mechanisms ( re-gauging) to 22.2mm Track ( S- Track, .875") and adding buffer-beams, draw hooks ( link couplings) and Square box headlights, etc,  and other purely QGR accessories, a reasonable  facsimile ofthe Originals  canbe acheived.

Also looking for an On3 Bachmann Baldwin 2-8-0 for the three QGR C classes, C13, C15, & C16...very similar to early DRGW locos.

How is the Bachmann frame made? Solid machined casting, plastic moulding, or plate frame??

Wheel sets can have axles replaced, & re-quartered, Cylinder blocks & Valve gear spaced out with spacer blocks 2.75mm thick each side; same for tender trucks. ( extended or new crossbeams)...maybe even S standard trucks ( oal may be incorrect.)

Now to source some not-too -expensive Bachmann On3 locos.


Oman posted:

I've nothing to add that would help you. I've often thought one of the manufactures should make On42 that runs on S gauge track; close enough. Newfoundland, Canada had 3'6" gauge.

The story I heard was that Bachmann considered building their models to run on S Gauge track, but went with HO track because of the ready availability of HO track, which they also already produced.

I'd say they made the right decision.


Resurrecting an old thread I just found:

I am a big fan of Newfoundland Railway and O scale, hence On42. I don’t currently model in the scale but since I already do O 2-rail and On30, why not add another gauge?!?

I have been thinking S scale mechanisms and equipment would be useful and (except for steam locos) easy to regauge that additional 1/16” or 1.5mm. I always hand lay my O scale track (except for snap-track layouts I have setup for years), so track wouldn’t be an issue.

We used to have 18” on our farm and I’d considered putting 18” on old roadbed between our little town of Emmett, Idaho and nearby Caldwell, Idaho- an amazing attraction of 25 miles of railway.

A loco builder heard of my wild dream and contacted me about what kind of motive power I was thinking. Of course I said 2 2-8-2 Mikados and 2 4-6-2 Pacifics about 1/2 size of Newfoundland Railway locos and 2 2-6-6-2s like those once at Sumpter Valley Railway.

He said they had experience building the Mikado/ Pacific types and could likely build multiple of them for about $300,000 each, first could be delivered about 2 years after payment received!

So I continue to dream in O and 1/20th large scale…

@prrjim posted:

It seems to me that the Bachman ON30 locos mechs would be too small - ie represent too tiny of locos for 42 inch mainlines.     They are already representing very small prototypes - some are 2 ft gauge prototypes.

I had thought of doing  0n42 using Rex engines, the proportion's are close enough to  0n3 or 0n30  in size . I have  5 or 6 siting in a box here.  S scale cars are also easy to convert

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