To run on most other people's tracks and to run most available stock on existing wheels chose the G1MRA Standard standard. Otherwise use 'dead' scale.

G1MRA Gauge One Fine was used out of fear that anything more accurate would not work.
The scale flanges common to ScaleOne32 and 'dead' scale do work and make Gauge One Fine unnecessary for me.
G1MRA Gauge One Fine is an excellent set of standards in reserve for the unlikely day when all G1MRA Standard standard users decide to change to something better, all at the same time.

Use ScaleOne32 if you want to accomodate existing G1MRA Fine stock. I have instead chosen 'dead scale' for the reassurance that the stock will comfortably pass through any dead scale 32:1 pointwork with less risk of binding on the check rails.

G1MRA STANDARD, 45.0 x 2.5 to 3.0 (Gauge x flangeway).
Wheels are 5.5 to 6.0 mm wide at 40.0 to 40.5 mm back-to-back on 1¾", 44.5 mm to 45.0 mm gauge track.
Wheel flanges are 2.0 mm deep for unsprung or not equalised wheels, otherwise 1.5 mm.
The 2.0 mm narrower back to back (than in Fine) can make a tight fit to get boilers etc between the wheels.

Unusual among model standards, G1MRA's standard wheel standard is not as coarse as its track standard. Due to this mis-match there is a problem with wheels dropping in at point frogs and wearing down the tip of the point. This is most noticeable with smaller wheels. It is a frequent topic in the G1MRA Newsletter/Journal with suggested solutions varying from filling the floor of the gap for wheels to run through on their flanges to off-setting the check rails. Sprung suspension, especially of heavier locomotives axles does help.

The new standards as in 2009 introduced tolerance of up to 0.5 mm in several dimensions (see the table). Chosing the narrower 2.5 mm flangeway option at the frog will provide support for wheels down to the new minimum width of 5.5 mm, but remember not to exceed the check rail span dimension of 39.5 mm, which forces a wider, 3.0 mm, flange way on the other side of the track. Remember also that chosing the narrower wheel option will make matters worse for wheels dropping in on the frog when visiting layouts which still have the traditional 3.0 flangeways on both sides of the track.

Some modellers change the back-to-back to 41.0 mm which will work with standard track dimensions, but the opposite check rail will only hold the wheel fully off the point of the frog for flanges of no more than 1.0 mm thick (the inner face of the opposite check rail to the face of the frog is still 42.0 mm). There is still the problem of a 6.0 mm wide wheel going though a 6.0 mm wide frog gap.

Chose this standard for running on most other people’s tracks.

Comparitive block diagrams of wheels in point frogs

NMRA #1 STANDARD (July 2004).

Wheels are 5.97 mm. (0.235 inches) min. wide at 39.8 mm min. back-to-back on 45.5 mm gauge track, flange depth 1.63 max. As set out I think there must an error somewhere unless they have different width flangeways on each side of the track as using the 2.68 flangeways both sides would give a span across the check rails of 40.14 mm, or 0.45 mm. greater than the wheel back-to-back. The actual specified check rail span is 39.69 mm. max. Applying their check gauge dimension of 42.16 to 45.5 mm track would make the opposite flangeway 3.34 mm.

The wheel width, 5.97 mm minimum comfortably exceeds the gap at the point of the frog which is 2.68 x 2 or 5.36 mm by 0.61 mm.

G1MRA FINE, 45.0 x 1.75 (Gauge x flangeway).
Wheels are 5.0 mm wide at 42.0 back-to-back on 45.0 mm track. Flanges 1.5 mm deep.

5.0 mm wheels cover the two flange-way gap in points with at least 1.5 mm spare for support from the opposite checkrail. It gives much smoother running through the points than does G1MRA Standard.

I used this standard for my garden railway up to 2005 with 1.5 mm deep flanges for sprung and non-sprung stock before changing to using exact-scale flanges.

Chose this standard if you prefer better running through the points, the look of thinner wheels and the 2 mm extra between the frames (compared with Standard).

The flanges being 0.6 mm deeper than in exact scale will give a little more protection from derailing on track where one side twists from higher to lower than the other. Equally, your track can be further out of level before you notice it.

Photo of wheels with scale and with fine flanges
Images above show a scale flange (left) and a G1MRA Fine, 1.5 mm deep flange (right) from form tools.

In this example the journals are 2.0 mm dia. to fit small ball bearings.


One or two modellers have used exact scale track and wheel standards for a long time. Recently more of enthusiasts have been dipping their toes into modelling at 1:32 and at as close to exact scale as they reasonably can and finding that it does indeed work.

The smooth running benefits of these track and wheel standards are just as much available to 10 mm/ft modellers who want better looking wheels and points.

If you are new to Gauge One modelling you will probably come up against a strong body of opinion from Gauge One Standard standard users who have tried nothing finer (than Gauge One Standard), that exact scale modelling will not work, or possibly just indoors. I regret to say that I was swayed initially by this traditionally negative attitude to model no finer than Gauge One Fine. I have since found by running scale wheels outdoors that it does work. I have also found that sprung suspension, while desirable, is not essential. My converted Diesel locos have no springs and the springs on much of the other rolling stock are too stiff to be of any benefit.

From Jan 2005 to October 2007 I had used dead scale flanges but with a back to back of 42.2 mm on my existing Fine (45 x 1.75 flangeway) track which gave me the option of also running on ScaleOne32 (45.0 x 1.5 flangeway), though not deadscale, track in future without further modification.
Following a satisfactory trial I immediately changed (Nov 2007) all the wheel back to backs to dead scale 42.4 to 42.5 mm and a few flangeways to 1.4 mm. The stock also runs through my remaining unaltered G1MRA Fine points with no problems.

The prototype gauge is increased by up to 3/4" on curves (= 0.60 mm scale) and this should be reflected in close to scale modelling.

'DEAD' SCALE (almost), (Prototype dimensions devided by 32), 44.84 to 45.44 x 1.4 (Gauge x frog flangeway), with modellers using their own discretion to get as close as they can to 1:32 by scaling from the prototype.

    SCALED: TRACK GAUGE 44.84 - 45.44, FLANGEWAY 1.39, CHECKRAIL SPAN 42.069, WHEEL BACK to BACK 42.3 - 42.56 mm.

Gauge: 44.84 to 45.44 mm. is equivalent to 4′ 8½″ for straight track, and 45.44 allows for ¾″ prototypical gauge widening on curves.

Gauge widening will have no effect on wheels passing through points as long as the frog flangeway, and the checkrail span are constant and are measured from the frog side of the track. Gauge widening should be within the outer flangeway (outside the guardrail).

The width over the check rails + one flangeway is 42.1 + 1.4 = 43.5 mm. The flange width is 1.0 mm, so without overlapping radiused wheel and rail edges, the maximum wheel back to back to fit the track would be 42.5 mm - before counting the small overlap which allows for a greater permissable b-b.

By measurement of a wheel generated by my formtool on a Tenmille Rail, I found that a nominal 1.0 wide flange placed the inner face of the flange just 0.85 mm. in from the rail. There was 0.15 mm overlap from the rounding of the rail and wheel flange root.
This gives a maximum b-b of 0.15 mm more, up to 42.65 mm. before losing benefit of the guardrail to hold the wheel off the tip of the point.

Note: To avoid wheels binding on the checkrails on widened track (eg. Llagas Creek at 45.8 mm), do not exceed the width across the checkrails of 42.07 mm. Any gauge widening should be within the outer flangeway.

Scale section rail sources:
  Bullhead chaired track: Cliff Barker. Rail section and chairs to scale but not the point flangeways.
  Flat bottomed track: Tenmille is close to North American 111 lb rail and fits Llagas Creek sleeper base.

For a very comprehensive list of prototype rail dimensions visit http://www.s-scale.org.uk/rails.htm.

The prototype wheel back to back varies a little, for example:
British, BR Standard bogie at 4′ 5½″, BR Class 22 Diesel 4′ 5⅝″,
American, Allegheny bogie 4′ 5¼″, Allegheny Drivers at 4′ 5⅜″.
Flange width towards the base scales to 1.0 mm.
This range from the smallest American 4′ 5¼″ (=42.27 mm) to the largest British, 4′ 5⅝″ (=42.56 mm), all passes though scale track of 44.8 mm gauge x 1.39 mm flangeway.

Tyre widths: Dead scale modellers are also likely to use scale wheel widths across the tyres where they can. These figures vary a little on the prototype with wear, tyre changes etc., so rounding to nearest 0.1 mm would seem reasonable: Wagons with 5″ wide tyres (=3.97) rounds to 4.0, but Locos are slightly variable and some research may be needed for your particular prototypes. Examples include the GER Clauds with 5⅜″ wide tyres = 4.27 which rounds to 4.3, and LMS Black Fives or BR class 22 Diesels with 5½″ wide tyres = 4.37 which rounds to 4.4 mm and LMS Duchesses with 6″ wide tyres = 4.76 which rounds to 4.8 mm.

The 10 mm/ft equivalent, or scaleten, track gauge for straight track would be 47.1 mm. I do not know of anyone modelling in Scaleten at present.

NMRA PROTO:32, 44.86 to 45.85 x 1.4 to 1.5 & 1.65 flange way at guard side (Gauge x frog flangeway) standards are set out at http://www.nmra.org/standards/sandrp/consist.html.

    TRACK GAUGE 44.86 - 45.85 min, FLANGEWAY at frog 1.4 - 1.5, at guard rail 1.65, CHECKRAIL SPAN 41.40 - 41.86, WHEEL BACK to BACK 41.88 - 42.37 mm.

The wheel back to back scales out at 4′ 4¾″ to 4′ 5⅜″.
The check gauge - or span across the check rails, is given as 41.4 to 41.86 mm. This narrower than prototype dimension is caused by overwide flangeways, up to 1.5 mm at the frog, and 1.65 mm at the guard rail side. Wheels with NMRA Proto:32 will pass check rails of this standard, but at the tighter end of the allowable range they will not pass through dead scale 1:32 pointwork where the 45 mm track gauge less two of 1.4 mm flangeways creates a span across the check rails of 42.2 mm.

The wider guardrail flangeway and narrower checkrail span would not quite hold the slightly wider British wheel back to back off the tip of the frog. In practice this may not matter as with reasonably well made scale points the wheels are lined up to pass safely through the frog anyway.
The maximum gauge of 45.85 mm allows for slightly more than prototypical gauge widening on curves which may be sharper than prototype on model layouts.

SCALEONE32, 45.0 to 45.5 x 1.5 (Gauge x flangeway), standards can be seen at http://www.titfield.co.uk/one32mod/Newstandards.htm and on the G1MRA web site at http://www.g1mra.com under resources.


The dimensions listed fall within the band of tolerances of, and are wholly compatible with the NMRA Proto:32 but are presented as "target" figures without tolerances.

These standards differ from 'dead' scale by the very slightly narrower than prototype back to back to provide an option to run on G1MRA FINE track, and also by specifying an arbitrary choice of tyre width for easier understanding.

If G1MRA FINE loses support there will be less reason to use this version of 'dead' scale.

The scale flange depth is 0.9 mm. so track needs to be well maintained and/or some vertical swivelling movement allowed on the axles of long vehicles to prevent derailing on track where one side twists up or down or 'winds'. The good news is that a shallow flange has less chance of being derailed by any projecting ballast.

In G1MRA Fine, ScaleOne 32 and 'dead' scale the wheels are generously supported as they pass through the points so there is no clatter of wheels dropping into the gap so familiar with the G1MRA STANDARD standard. I have succesfully tested quite long trains with scale flanges wheels at speed on an outdoor, garden layout. These standards are not just for small indoor cameo scenes.

Wheels at about 39.5 mm to 40.0 back to back with deep flanges on 45 mm track.
LGB and several other manufacturers using their own roughly similar sets of dimensions.
Some makes will run on G1MRA STANDARD depending on the particular chair or rail clip profile of the track, otherwise chose this standard to avoid having to replace the wheels of G SCALE models.
The flaw in the design of the G1MRA Standard standard of wheels dropping in at the point frogs is dealt with by using wider wheels of 6.5 to 7.5 mm.

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29 Mar 2013