Further work on Modular standards

[IanT]

As I had just published the previous 'track clearance' recommendations made by Alan Marsden, I thought it would make good sense to check my initial CAD model against his ideas. I therefore drew a twin track (with a 4500mm inside radius at 160mm centres) and placed two BR carriages on it (as per Alan's original practical experiment). I found that the two carriages passed – but only just. I "measured" the passing clearance at just under 12mm (see PDF print out of CAD drawing attached) and of course this is a static model. Stock will sway sideways at speed.

I then had a good look at NEM103 & NEM112 to check their 'Standards' in this area. They use three defined maximum carriage lengths to define clearance on curves, together with a table of value 'E' to give the required clearance. In NEM the normal clearance of a straight track is called 'B1' and on a curve they define the required clearance as being 'B1+2E'. What NEM does not give is the formulae they have used to calculate 'E' but I found this in one of the Spur II standards. It takes the radius of the curve and the distance between bogie pivot points to arrive at 'E' but also assumes that vehicles fit the three standard 'max' sizes defined by NEW103. Armed with this information, I built a simple spreadsheet to calculate 'E' for our proposed standard curves.

I should note that the A, B & C sizes are for Continental loading gauges, but that a BR Mk3 sits between the A and B lengths. To simplify matters, I therefore decided to use size 'B' as my norm.

Initially I felt that we should publish a new standard ("M02") to give the required clearance for each of the standard curves proposed in M01. Indeed I have written a draft 'M02' on this basis.

However, on thinking about this, I decided that the recommendation could (and should) be simplified.
The first simplification should be that twin-track modules should not normally be built at the 1500 & 3000mm radius. I feel that these should be defined as 'single track working' in the standard. This left the other three radii with (calculated) recommended clearances of between 192 and 180mm. Again, I feel that this should be simplified (and given that there is already some tolerance in the calculation) that a single clearance on all three should could be set to 185mm.

Having reached this conclusion, I was left with the issue of the "transition" module, which would enable the track spacing to move out from 160mm to 185mm. NEM give this as a distance of >15xGauge (952.5mm in G3) but a single 900mm module should be sufficient. However, this transition module would be required on both entering and leaving any twin track curve. To be clear, this is a track widening transition, not a 'transition curve'.

My original concept was for a modular track system that was "Hornby-like" in terms of plug and play. Introducing transition modules etc would have made life much more complicated than this.

So my thought at the moment, is to recommend a very simple system for twin track modular clearances. This is to adopt a new track centre-to-centre dimension of 185mm across all modules, both straight and curved. We would not recommend twin track operation for 1500 & 3000mm curves.

I am sure that some modelers would prefer to keep the 6' way on straights (the current 160mm scales to 7') but I believe that this approach has merit in its simplicity. Anyone wishing to build moules to strict prototypical dimensions can do so - as M01 allows for the concept of "Custom" modules.

Regards,

Ian T

[IanT]

My first post in this topic was getting a bit long - so I decided to add this second part.

If anyone would like to see copies of the spreadsheet I've used (or the draft 'M02') then I would ask that they contact me directly by email. I will also be re-writing the draft 'M02' to reflect my conclusions, as also outlined in the first post. I also have copies of the NEM & Spur standards in .pdf format - although these can be found online.

I know that a number of you are considering building 'Modular' and may have already done so. I currently have six modules built to the original C3 standard - but I intend to make 'adaptor' sections for them so they can connect to M01 modules.

I also have some older track sections that were used some years ago at exhibitions and I intend to completely rebuild these to the M01 standard. As these may involve some twin track (straight) sections, I would like some agreement on the dimensions - preferably from Members who have a direct interest in this area.

Whilst I am more than happy to hear anyone's views on these ideas, I will be particularly influenced by those who actually want to build Modules, as I feel that in practice, it makes sense for you to have a louder voice.

In this regard, would anyone be willing to build at least one 900mm module to take to the AGM in February?

Regards,

Ian T

[MikeWilliams]

Ian,

Yes, probably.

Due to time constraints it would be easier for me to build a module if somebody else designed the structure and provided a cutting list.  I know the M01 concept allows for any form of construction, but if somebody else is prepared to do the hard work and prove the design I'd happily copy their drawings and make one.  I'm thinking of 6mm ply, half-lap joints pinned and glued with fillets in the corners (or similar)?

Taking that thought further, maybe somebody is prepared to have a batch of timber parts cut by a local timberyard and offer kits for the whole structure, leaving us to assemble, lay track and add scenics?

Mike

P.S. Thanks for all your work on this Ian, sometimes a thankless task I know, but it brings the idea of a portable Gauge 3 running track a little closer.

[IanT]

As described below – you will know that I have been working on defining clearances for twin-track curves. This resulted in a recommendation that a single 185mm distance between track centres on twin-track curves be adopted. The simplification that this provides then suggested the same distance for clearance for straight twin-track. This eliminated the need for 'transition' modules before curves.
When I came to redraft M01, I realised that it also made the definition simpler too. I have not therefore needed to produce a "M02 Clearance" standard as originally intended. I've simply incorporated the changes into M01. I've also redrawn the C3 connector diagram, which I hope will be a little clearer now.

I should make clear that the original 'single-track' definition within the M01 Standard remains unchanged. It's really just the spacing of 'twin-track' modules that has been addressed.

I know that some Members will not approve of this non-prototypical (e.g. non 6ft way) design but I think the practical advantages and simplicity makes this change worthwhile. Members who wish to use prototypical clearances can still do so within their own 'custom' modules. This also applies to existing exhibition layouts which I hope to be able to inter-connect using standard C3 modules (if their owners are willing). It only requires two 10mm diameter holes in the right place.   

Having finished this revised definition last night, I have been thinking about the practical application of the design. From my personal point of view, I suspect that I may now standardise on 635mm x 900mm modules, even where I am only planning single track sections.

The extra cost of a 635mm (versus a 450mm wide) module will not be great, the main overhead being building the module in the first place. So if I build 635mm in width, I will achieve a coherent module look between both single and twin track sections and if I want to add a second track in the future, then I have the space to do so.

However, people still have the freedom to use the narrower single-track section if they prefer. This has been left unchanged and modules will still inter-connect seamlessly on the 'front'.

I am now planning to build some modules to the new standard. I will build some simple straight 635 x 900 modules first, although I'm not sure if they will be single or twin track at this time. Then I will work on a multi-section module including one or more turnouts, possibly a crossover between twin tracks. The standard leaves the build method open to the individual, although I have found some interesting ideas on the Spur II site (by looking through their photo-gallery).

I have asked our Webmaster to make available the latest PDF version of M01 and I would appreciate your thoughts & feedback. If anyone intends to build a module (or two) I would very much like to hear from you. Several Members are thinking of doing so but I think some discussion & co-ordination might be useful in these early days.

Regards,

Ian T

Download link :
http://lakes-pages.com/gauge3orguk/M01.pdf

[dajo]

I am very interested in this topic because I have been thinking about making my own portable track.
Accordingly I have read, and I think understand, the design work that has been done for M01.  And I
have found the NEM and Spur-II stuff on the web.  It is all hugely useful to me, if only as a sanity
check.  I shall be filtching a lot as I progress with my own plan.  In the Autumn 2011 Neswletter
Ian asked for feedback, so I decided to write what is below.

Now, I did not know what is a "6ft way".  But I have worked out that the 6ft refers to the spacing
between the adjacent rails of adjacent tracks - someone please correct me if this is wrong.  6ft way
thus uses a centreline spacing in Gauge 3 of close to 145mm.  160mm (about 7ft way) has been
introduced as a possibility, although I do not know the history of that.  And, in M01, Ian suggests
185mm (about 9ft way) for the practical simplification reasons he gives.  Now taking the straight
module width as 600mm; and expressing the M01 across-the-module dimensions in a slightly different
way to that in the M01 specification, this gives centreline spacings of 225-185-190.  Why not move
things a little and make the spacing the delightfully simple 200-200-200?  200mm corresponds to a
slightly more than 10ft way.  As Ian points out, spacing within any given module is not bound by
this inter-module interface.

In addition to the obvious simplification for one's mind, I note that this spacing can eliminate the
distinction between the front and the back of a module.  In the case that "reverse" curves are used
this could be another useful simplification.  For example, a kidney shaped track instead of a plain
oval might be quite practical because a curved module could be used in either forward or reverse
sense.

I note that 600mm is given as a minimum dimension and a spacing of 200-200-(200 + X) would result in
baseboard fronts not lining up if the module were used in reverse.  But a module builder would be
aware that he was creating a wide module with the consequent characteristics.  And, presumably, such
a module simply would not be used in an awkward way.

Also, I wonder why the baseboard front edge is being used as a datum reference for inter-track
relative location.  It seems to me that the correct way to dimension the interface is from the dowel
holes.  And, indeed this is partially done with the 66mm drop and the 61/122mm separation for each
track.  Surely, twin track separation should be done using this interface?  Using a 185mm track
separation the horizontal separation of the two inner holes thus would be (185 - 2*61) = 63mm, and
using a 200mm separation this would be 78mm.  And the key point is that the baseboard (front) is not
involved in twin track location; the latter being hard enough between modules made across time,
space, and creator. I understand the need to position the baseboards relative to each other,
including the desirability of having the fronts line up; but this should not be coupled with the,
far more crucial, relative track locations.

But there are further questions, too.  One is, why is a single track located using two holes?  There
is a redundancy in this set-up that easily can cause manufacturing and fitting problems as the
number of tracks increases.  I fail to see why four holes are required in M01 to locate twin tracks.

I shall stop here because I have found information in another place - Connect 3; this explains the
7ft way for example.  I shall do some more hunting; but I think that the two or three points above
are valid, although they may be too late to have any importance.

dajo

[IanT]

Hallo David,

Thank you for your post - as you say some interesting comments that I will have to think about - but I'm afraid not tonight, as other things are waiting.

But very quickly - the "six foot" way is normally measured from the two inside rails of each track (and from the rail top centre).  So the distance between track centre lines will be the "way", plus the track gauge, plus one rail top width (two halves if that makes sense).

The reason I have used the concept of "front of module" is because that is how the Spur II guys defined it, and the mechanical connection (e.g. the holes) and the distance of the centre line to the track edge in M01 are compatible with the Spur II standard - so we could in theory go to Germany and connect our modules to theirs. Not a bad idea for some time in the future perhaps...   

To be honest, any 'standard' is probably going to be pretty arbitrary in terms of many of the dimensions (and of course you could use different sizes/datum points to suit your own specific needs or preferences). The key to any 'standard' is simply that everyone agrees to use the same ones!

I will look at this in more detail though when I have some spare time next week and respond more fully then.

Thanks for your comments and I hope that at least the M01 standard has helped you think through some of the issues anyone building track modules in our guage/scale might have.

Regards,

Ian

[MikeWilliams]

This topic has been quiet lately, so can anyone please confirm whether the standards are now set, and confirmed?  I seem to recall a year ago they were tentative for comment, so can we now assume they are agreed and use them?

Thanks,

Mike

[IanT]

No, they haven't changed since then Mike and if we want to retain a level of 'mechanical' compatibility with the Spur II standards (and I would like to get over to Germany one day) then they probably won't change too much now either.

However, Spur II do not define any aspect of twin track operation (at least within their modular standard) which was something that I felt was much more likely to be required over here. As I was looking at the other issues surrounding clearance at the time, I thought it would make sense to incorporate some guidance in this area sooner, rather than later.

As you know some compromises were required in terms of the spacing on curves but nothing too serious I believe, at least when compared to worrying about longer vehicles having sufficient clearance on a modular track - as I've detailed below.

So, no changes to any fundamentals planned, so please go ahead with building your modules.

I didn't have enough rail/chairs to finish my Mk2's at the time but that been solved now and it's only the colder weather that's keeping me inside. They will be 5 x 900mm (14 3/4 ft) sections of twin track (including the crossing). Looking at the various viaducts on show on Saturday - I think my older (narrow) Mk1's could give me another 18ft (or 9ft of twin track) if deployed as a viaduct. They will need two Mk1 to Mk2 'adaptor' plates at either end (and some cosmetic work) but I will then have about 24ft of straight twin track modules to play with and I can start looking at building some curves....

David - I've also realised I owe you some more commentary that I promised a while back - my apologies - I've been somewhat occupied with other things lately but I will look at your feedback and respond to you shortly.

Regards,

IanT

Further developments on this module can be found here : http://lakes-pages.com/gauge3.co.uk/G3Forum/index.php?topic=891.msg4741#msg4741