Actual Track Gauge

[Art Dent]

Hello folks,

 

As mentioned in previous posts in this forum, I am new to O-gauge - so have a few 'noob' questions.

 

Trying to establish the scale we are working to here in order to plan the correct 'gap' between rails (the 'Six Foot').

 

I had assumed 1:43 however a quick google reveals that there are several different "standards" for O-gauge!

 

For example, the track gauge for normal standard gauge track seems to be anywhere between 30mm (1:48), 1.25in/31.75mm (1:45.2), 32mm (1:44.8), 32.96mm (7mm:1ft) and 33mm (1:43.5) - these last two being virtually identical.

 

So, what scale are we working to here in the UK - I'm guessing 7mm:1ft or 1:43.5 - but that's a guess.

 

Apologies for the 'noob' question.

 

Art

Edited September 17, 2018 by Art Dent

[N15class]

British o gauge is a scale of 1/43.5 or 7mm/ft. With a gauge of 32mm, some use 31.5mm to avoid wheel drop. Scale 7 is still 1/43.5 or 7mm/foot. But with a gauge of 33mm.

You have to avoid getting scale and gauge mixed up. Unfortunately the likes of the RTR manufacturers have been miss leading the public for years.

[Gordon A]

Just to add more confusion, standard O gauge, O gauge fine or Scale 7?

 

Applicable to O gauge - 7mm to 1 foot.

 

Gordon A

[tender]

......some use 31.5mm to avoid wheel drop. 

 

 

Another novice here, but doesn't the 31.5mm gauge use 1.5mm flange ways instead of 1.75mm to avoid wheel drop? O-MF?

[Simond]

Indeed. Peter is correct, and as Tender says, the flangeways that go with 31.5 gauge are 1.5mm to avoid wheeldrop. This is better looking, which is a bonus.

 

S7 is “true scale”, or at least, can be, in principle, it allows models to be built with dead scale flanges, and clearances, and avoids some compromises in modelling such as different frame widths above and below the footplate, and adjusted wheel centre distances to allow for oversize flanges. It does however require compromise in curve radii, as large locos require scale curves, and scale curves are quite large.

 

0F, (0-Fine) with 1.75mm flangeways and 32mm track is the de-facto standard for 0 gauge, and in principle, 0 gauge models will run on it, unless they are intended for coarse scale, which, just to be confusing, is sometimes referred to as “standard” by older modellers. Coarse scale caters mainly for legacy products, though there are several RTR suppliers including Ace Trains & Daersted.

 

0MF (0- Modified Fine) is another compromise, brought about by a move towards more scale wheels, which were narrower than those originally made for 0F. This led to wheel drop at crossing noses, and thence to finer flangeways. As I said, it looks better, though some people argue that “it can’t be better because it’s further from scale”. Well, in my opinion, it is much easier to see a quarter of a millimetre in one and a half millimetres, than it is to see a half millimetre in 32 mm. Try it.

 

The clincher from my point of view is that I can run my stock on my pals’ layouts and vice versa, coupled with which, all 0F RTR stock works on 0MF, and the majority of second hand stuff will run on it too.

 

So 0MF offers better running and better appearance, but, there’s always a but, you do have to make your own points & crossings. I’m not sure that anyone offers RTP trackwork to these standards, though Marcway may do it to order. I enjoy track building, so it suits me. I would note that you can build 31.5 pointwork, and connect it to 32mm plain track, indeed, if your curves are under 5’ radius, I’d advise it.

 

My conclusion is that 0MF works for me. If you want the ultimate in museum quality models, talk to the S7 crowd. If you don’t want to muck around building track, stick to 0F, and if you like old Hornby, clockwork, live steam, glossy locos and stock, then consider coarse/standard scale.

 

Hope this helps!

Simon

[N15class]

Another novice here, but doesn't the 31.5mm gauge use 1.5mm flange ways instead of 1.75mm to avoid wheel drop? O-MF?

Yes it is but S7 is yet another. I was leaving out the details to try and stop even more confusion. And point out scale and gauge are not the same. With 1/43.5 that we mainly use in the UK. You can still build models that run on 16.5mm gauge track, (00 gauge, to the 4mm modeller), or whatever gauge you want within reason.

Yes it can be confusing, but once you learn you build to a scale not a gauge it all becomes clear, then add the gauges it all becomes mud coloured again.

[brack]

Commercial track is 32mm gauge. Kit and RTR stock will run on this. These days some people use 31.5mm for improved running and appearance (tighter tolerances through points etc). Normal kit/RTR stuff and wheelsets run fine on this too and if you're handbuilding your track it isn't any harder/any more work.

Some people use 33mm, but this requires a much tighter set of standards and different wheel profile, so extra work will be needed. This is called scaleseven / S7.

All British O scale is 7mm/ft or 1:43.5 (practically meaning the same thing).

[Nearholmer]

Dare I add further confusion by mentioning the standard that I use ....... probably best not!

 

Yours coarsely, Kevin

[HSB]

US models are built to 1:48 scale and run on a nominal 1 1/4" gauge (which actually scales out at 5' gauge) while most RTR European models are now produced in 1:45 scale to run on 32mm gauge. As the previous posters have stated, British models are produced to 1:43.5 regardless of wheel and track standards.

[Nearholmer]

Is US 0 gauge track still actually 1.25” ?

 

I was under the firm impression that it had become 32mm.

 

The difference is only c0.25mm, and of no practical importance to me; I’m just curious.

 

The very earliest set of 0 gauge track and wheel standards were produced in England in 1909/10 by Henry Greenly, and he specified 1.25" / 31.75mm, see page 25 in my thread for more detail of early 0 gauge track and wheel standards.

Edited September 18, 2018 by Nearholmer

[NHY 581]

I have the same issues trying to understand all of this. Thanks Simon et all.

 

 

Rob.

[meil]

Is US 0 gauge track still actually 1.25” ?

 

I was under the firm impression that it had become 32mm.

 

 

Except that those who model P48 in which case it is 29.89mm.

[Happy Hippo]

I have the same issues trying to understand all of this. Thanks Simon et all.

 

 

Rob.

In 4 mm terms it's the same can of worms you get with P4, EM, OO, OOSF, etc.

 

There are fewer worms in the can ('coz they are bigger).

[Art Dent]

Wow!

 

I hadn't realised (although I suspected) that this was a can of worms and it seems to be the case (much the same in OO)

 

So, in summary, here in the UK both RTR manufacturers and modellers use 1:43.5mm scale and a track gauge of 32mm (I'm not talking S7 / OF / OMF here).

 

Still climbing the learning curve!

 

Art

[polybear]

Perhaps there's a need for 0-SF (or 7-SF if you prefer)?

 

Too late. Hat on, coat on, half way down the street......  

[Nearholmer]

“So, in summary, here in the UK both RTR manufacturers and modellers use 1:43.5mm scale and a track gauge of 32mm (I'm not talking S7 / OF / OMF here).”

 

Yes.

 

The history of the gauge is pretty clear: it started with German tinplate track with a distance between rail centres (not inner faces) of 35mm, each rail having a radius at the head of 3mm; ergo the distance between faces (the gauge) was 32mm; in creating a standard for track and wheels that worked for both tinplate and solid rails in 1909, Greenly did two things at once, he anglicised to 1.25” and gave a metric equivalent of 31.75mm. Practical tolerances for these purposes in 1909 were such that having three figures, 32mm, 1.25”, and 31.75mm made not a jot of difference. Subsequently (looong story) 32mm has become the standard dimension in Europe including the UK.

 

Within the chosen gauge, there are a plethora of sets of standard wheel and point-work dimensions to choose from, the most popular in the UK having for the past fifty or so years been Gauge 0 Guild ‘fine’, but others have significant followings too, G0G ‘coarse’, S7 etc etc.

 

In 1909, scale, as opposed to gauge, was a tad indeterminate. Greenly drew lineside structures at both 0.25”/ft and 7mm/ft, and flipped about between use of imperial and metric units. Some ‘hi-fi’ enthusiasts built rolling stock to one scale, some to the other, and wide-market commercial models were to ‘it looks about right’ scale. After another set of looong tales, the settled position came to be that the USA adopted 1:48, German-speaking countries 1:45, and Britain and France 1:43.5, with exceptions.

Edited September 18, 2018 by Nearholmer

[Art Dent]

 

 

“So, in summary, here in the UK both RTR manufacturers and modellers use 1:43.5mm scale and a track gauge of 32mm (I'm not talking S7 / OF / OMF here).”

 

Yes.

 

In 1909, scale, as opposed to gauge, was a tad indeterminate. Greenly drew lineside structures at both 0.25”/ft and 7mm/ft, and flipped about between use of imperial and metric units. Some ‘hi-fi’ enthusiasts built rolling stock to one scale, some to the other, and wide-market commercial models were to ‘it looks about right’ scale. After another set of looong tales, the settled position came to be that the USA adopted 1:48, German-speaking countries 1:45, and Britain and France 1:43.5, with exceptions.

Thank you for the clarification Nearholmer.

 

I'll go with 1:43.5mm scale and a track gauge of 32mm

 

Art

[sir douglas]

it always confuses me that the finescale people chose to go down to 31.5 instead of up to 33 which more correct to scale such as the EM/P4 versus OO. surely you can just pack out the back of slaters wheels with washers to put the back-to-back to 30.5mm

[N15class]

it always confuses me that the finescale people chose to go down to 31.5 instead of up to 33 which more correct to scale such as the EM/P4 versus OO. surely you can just pack out the back of slaters wheels with washers to put the back-to-back to 30.5mm

The wheel profile is wrong for S7.

[Simond]

You can set your wheels & track to anything you like.

 

If you want better running & better appearance but to retain compatibility with your pals’ stock & track, then 31.5 makes sense.

 

If you want prototype fidelity, go 33.

 

They ain’t the same.

 

Best

Simon

[dajt]

If you're changing the wheel b2b of an existing steam loco built or designed for 32mm gauge then narrowing the gauge by 0.5mm may be easier than widening it by 1mm. Probably doesn't matter as much on a diesel or electric.

 

But the points raised by N16class and Simond are more compelling.

[Simond]

Just to be clear, if you use 0MF, you do NOT change the wheels or gauge of your stock.  The only things that are altered are the gauge and the flangeway width through crossings.  You may choose to use 31.5 gauge for all track if you wish, however many of us use 32mm for plain track.

 

The whole point of 0MF is to make a track specification that works better with standard off-the-shelf wheels than the G0G standard for 0F, which has been superseded by the changes in commercial wheels over the last 10 years or so.

 

Here's a simple selection tool

 

1   Do I want to run Coarse Scale, old clockwork, similar stock?  If yes, then choose appropriate track and don't worry about this discussion.  If no, then go to question 2

 

2   Am I prepared to build points and crossings, or have them built for me?  If no, choose G0G 0F, use RTR points such as Peco and Marcway, and don't worry further.  If yes, go to question 3

 

3   Do I have a collection of existing 0F stock, and/or want to run RTR stock without modification, and/or run my trains on my club/pal's 0F layouts and/or have pals run their 0F stock on my layout? 

     If yes, consider 0MF for better running, and better appearance. 

     If no, consider S7 for better running, better appearance, and greater scale fidelity.

 

Remember that you can mix 0F with 0MF on the same layout - fiddle yards etc can happily be laid with RTR trackwork  - the stock will run on both.

 

hope this helps

Simon

Edited September 26, 2018 by Simond

[Nearholmer]

Simon

 

I've become a bit of an 0-scale standards trainspotter since getting into the history of all this, and I think my library of standards is now out of date.

 

Has the G0G recently revised 0 Fine? If so, do you know whether the latest version is on-line anywhere?

 

Kevin

[N15class]

GOG o gauge standard fine is still the same, 31.5 is not a standard by GOG.

 

Whether GOG coarse standard has changed I do not know.

[Nearholmer]

I get that 31.5mm isn't a G0G Standard, but Simon, or another, hinted in another thread that there had recently been minor revisions to G0G Fine.