Scale and Gauge is perhaps one of the most LETHAL subjects for any railway modeller. So -I suppose I had better explain why I am tackling this most dangerous of topics here. It is generally accepted that 32mm track is the smallest practical gauge to use outdoors, (yes I do know of 16.5mm track layouts and 9mm layouts), 45mm track has a long and glorious history in the garden, but I am about to expouse the wonders of something very rare...

I have built and will continue to build 16mm scale models and it is very easy to adapt this to the 32mm and 45mm track -thus giving 2 foot and metre gauge track equivalents. however there is another narrow gauge standard that seems to be very uncommon in the 16mm world -The Cape Gauge of 3 feet 6 inches.

This originated in Norway and is the invention of Cap Phil.

Now that I have moved and I have a HUGE back garden I have decided to turn my attention to this. There is a group who have devised the "T" gauge of 56mm which is mathematically the correct gauge but this would require totally hand made, (and everything else), track. This DOES appeal to me!!! However, what I have decided to do is widen the gauge to a scale 4 feet and use Gauge 3 track work 63.5mm instead. This should give me a more stable locomotive and more importantly I can now fit the massive motors between the wheels that will give my articulateds the traction that they really need.

I will have to build all the trackwork myself -a job I am not looking forward to! So, why did I elect to go to the 63.5mm track rather than the "T" gauge of 56mm . The simple reason is multiplicity of use. On my 32mm track I can use the rather antique hand me down Basset Lowke locos and rolling stock from my father and the two "O" gauge clockwork Hornby locos from my late uncle. On my Gauge 3 track I will be able to use the "Cape Gauge" 16mm models, genuine Gauge 3 locos and 1 inch scale narrow gauge locos.

The following drawing shows the sizes of a Cape loading gauge for a locomotive at 16mm scale, (1:19.1), in yellow, and a British loading gauge for a Gauge 3 locomotive at 17/32ths scale, (1:22.6), in green.

After several failed attempts with spacing the sleepers and trying to find suitable rail I have elected to go with a perculier hybrid that looks slightly wrong no matter what sort of loco I put on it -but is acceptable to all!!! The track, (and as I type the epoxied jig for it is curing in the oven), is a combination of "Brandbright" wood sleepers and scale brass track with white metal chairs from "The Gauge 3 Society".

Having a collection of Henry Greenlys (HG) books along with Lillian Lawrence (LBSC) gives me some insight as to how "classical" pre-WW2 track was made. I sat down with HGs book on model railways I worked out (from the formulae there) what the sleeper spacing should be for 16mm, G3 scale, and Inch scale. What surprised me was the small differences that even a couple of millimetres could do to how the eye sees the track.

The G3 interval worked out at 32mm. This looked simply AWFUL on 16mm and Inch scale

The 16mm correct interval worked out at 40mm. This looked far too wide for G3 and slightly wide for inch scale.

The Inch scale interval worked out at 35mm . This was too wide for G3, too narrow for 16mm -but it the one that everyone looked at and said - "Er maybe?"

As a last ditch effort I used the recommendations of HG that the sleeper spacing should be 1 per 1 1/2 inch and well it it did at least look semi acceptable on all three scales... So this is the one I have decided to go with.

The next problem that has arisen is that of the curves. I have elected to use tangential curves of 2.4m radius (8 feet). This is classed as a "normal" curve in the HG source books. The test piece was to use a length of string and a pencil and draw it across a piece of 2mm squared graph paper. After several attempts (caused by laughter) I managed to get a "pure" curve at 2.4m radius. I measured it and found that it was exactly 4mm in 280mm. i.e. the curve dipped 4mm across the 280mm of the sheet of A4.

Having begun to "formalise" how my new railway will run -the SM32 track will be the inner of the two tracks -this will enable my son to have his spur to his "shed" which will enable him to run Toby and Percy and the troublesome trucks. The track spacing has been the source of some amusement(?) to me. The main problem is the fact that the loading gauge for my SM32 track is 12cm wide and the Cape gauge loading is 16.8cm wide. THUS everything will work well when they pass on a straight -but on a corner things will smash together...

My son asked me a question"What are the other gauges 4 and 5?". I could not answer -so I asked a forum. This is the reply:

Ralph,

The model gauges were originally quoted by the continental manufacturers as rail centre-to-rail centre which produces some confusion (I have a 1906 B-L French language cat which gives all the gauges on this basis, '0' is 35mm and '1' is 48mm, for instance) but, for what it's worth and using the GB measurement method, '4' is generally 3 1/4" (but has been a bit of a movable feast in the past, being quoted by some as 75mm) and '5' is 125mm (sorry about mixing units). The '0-5' system does miss out some extremely popular and widely-used sizes such as US Standard Gauge (2 1/8") and US Wide Gauge (2 7/8" ~ not far off the new 'F' gauge) which is probably the closest equivalent to 16mm SG that is still in any sort of production (best not to mention 'T' in case it gets too popular).

Cheers, Mike Dockery.

Here are some notes on the various international loading gauges:

See Loading  Gauge.pdf