BG13.5 Broad Gauge in Gauge 3

geoff_nicholls

Western Thunderer
I first started talking about modelling Great Western broad gauge mainly to tease Unklian, but it appears I've been hoist with my own Petard, and can't stop thinking about it myself. What made it worse was having to walk past North Star every time I wanted a cup of tea, at the Swindon show, and the presence of Alma Street Quay and Chalfont.
So, I've been thinking through how one would go about producing a broad gauge micro layout, while I carry out the more menial tasks on my proper layout Aldeburgh Wharf.
I checked the Broad Gauge Society technical standards:
BGS - Standards
and found they take a pragmatic approach: using finescale standard gauge standards (EM, P4 and S7) and just increase the back-to-back by the difference in the gauges.
For gauge 3, if we assume 7' 01/4" equals 95mm then using the G3 soc standards:
Gauge 3 Society
The back-to-back is (95-63.5) + 58 or 89.5.
The current G3 flangeway standard is 3.5mm, which some think is a bit generous.
My own limited space, modelling indoors, means my curve radius is only 3 metres, which limits how much I could reduce the flangeway myself, perhaps it could be 3mm?

Has anyone else had any similar thoughts? And a question for existing BG modellers in other scales: is it just the same as standard gauge, but with longer axles, or is there some part of the geometry that makes it fundamentally different?

None of the above commits me to doing anything about actually producing any models, although I do have two 4 foot by 2 foot grainge and hodder boards sitting idle until GRS begin selling W and U carriages again.
 

Spitfire2865

Western Thunderer
Seeing as BG and SG was used together in certain areas, Id expect them to be similar geometrically, or at least compatable.
Would be nice to see dual gauge working in G3.
Also, as G3 standards are relatively close to scale, I dont think there would be much issue.
Unless I am very mistaken.
 

unklian

Western Thunderer
I have been having a long think about this, and despite it being a tease by Geoff there is a serious side to consider.
Long ago the Broad Gauge Society decide to adopt Scale standards for track and wheels in 2, 4 and 7mm scales. So for example BG4 is Scalefour widened to 7' and 1/4" at correct 4mm/foot 1:76.2 scale.
Unfortunately there is no official set of S13.5 track and wheel standards for Gauge 3 1:22.6 13.5mm/foot scale . And I am sorry Trevor Spitfire the Gauge 3 Society standards are a long way off scale . I did a comparison here G3 Track and wheel standards.
So the question is wether to follow the BGS example and set out scale standards, or simply widen the G3Society ones. As a comparison with Geoffs dimensions track gauge would be 94.68mm , back to back 91.35mm and check gap or flangeway 2mm max for scale standards.
There is then of course the problem of making mixed gauge track and which set of standards to adopt for both gauges. Personally I am heading for scale standards but not just yet ! The big advantage of most Gauge 3 is that as long as stock is built sprung alteration between the different standards is relatively easy .
Food for thought, but please don't tell them 'over there', the whining will go on for months ( even though of course few of them model G3 ) .

FaringdonAries.jpg Aries at Faringdon late 1870's .
 

Spitfire2865

Western Thunderer
Was not aware of the limitations baring general coarse wheels.
Good read regarding SpurII though. The Germans get all the fun toys.
 

geoff_nicholls

Western Thunderer
After my experience of building a layout with inlaid track, I sympathise with Ian's argument. the gap between the rail and check rail was really noticeable. As is the mismatch between the actual frames of a gauge 3 model loco, and any parts of the frames above the footplate.
However for me, as an indoor gauge 3 modeller, there are practical issues: I'm sticking with 3 metre radius curves and turnouts, because that's the largest radius practicable for a layout in a room 12' 6" long. I find I already need to think a bit more about how to build locos and stock which can navigate tight curves. My modelling heroes Graham Overton and Jas Millholme were both innovative in their response to the problem of tight curves, with excellent results. My own ECR class A 2-2-2WT (the subject of my Avatar) has a stepped frame, narrower at the rear.
Gauge 3 Fine Scale would take a lot of effort, but the difference should be noticeable.

I wonder if they have a similar debate in 5" gauge?
 

JimG

Western Thunderer
Geoff,

My modelling heroes Graham Overton and Jas Millholme were both innovative in their response to the problem of tight curves, with excellent results.

When I was editor of the SSMRS Gazette, I published an article by Jas on one of his 0-6-0 locomotives which has a Cleminson arrangement on its driving axles to enable it to get round the curves on Jas' Yaxbury layout - quite a setup, and it works. :):):)

Jim.
 

AndyB

Western Thunderer
I wonder if they have a similar debate in 5" gauge?
The GL5 standards are here Geoff: Standards – GL5
If their wheel profile drawing is to scale then their flanges look to be similar in proportion to the G3S standard.
I think I did include the GL5 standards in a comparison I did some months back, but don't have the data to hand right now.
I'll see if I can find it later.

Andy

Edited for clarity.
P.S. Found my data, but it is in AutoCAD - so need to extract / screenshot it somehow.
 
Last edited:

AndyB

Western Thunderer
Here is the comparison I did. I hope it makes sense without a lengthy explanation.
I basically 'normalised' a whole range of standards (full size, model, historic and modern) to the G3 track gauge.
The GL5 profile is shown in yellow (sorry, it doesn't show too well on a white background) - when scaled to G3, it has the same flange height but slightly bigger B-2-B (59mm), and slightly narrower overall width.
Below the table are my doodlings to show that by reducing the flangeway by only 0.5mm, we significantly reduce the risk of flanges hitting the crossing nose and wheels dropping into the gap just before they meet the nose.
By doing this we should have improved running using any wheels that meet the current G3S wheel standard.
Of course, going to exact scale wheels and track totally removes that issue and enables us to put our frames the correct distance apart!

Andy
 

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David Taylor

Western Thunderer
I wonder if they have a similar debate in 5" gauge?

5" gauge standards are different between UK and Australia. Someone down here built a loco with UK standard wheels assuming things would be the same and it couldn't run on our tracks. We also have two different scales for standard gauge down here - 1 1/6" : 1ft and 1 1/8" : 1ft. Our wheel profile is such that the flanges are massively overscale and look terrible. But the track they run on is equally dire so it's a lost cause trying to make it look good in the wheel/track department. 5" gauge is not the place to go for fine scale. Robust is perhaps the word.
 

geoff_nicholls

Western Thunderer
by reducing the flangeway by only 0.5mm, we significantly reduce the risk of flanges hitting the crossing nose and wheels dropping into the gap just before they meet the nose.

I spent some time yesterday filling the gap between the rails at the frogs of the Cliff Barker turnouts on my layout. the gedunk really spoils things on a small layout where you get close up to the action.
 
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