Dimensions of Irish Prototypical points

[DiveController]

I was wondering if anyone could shed some light on point dimensions, in terms of the length of points from (say,) the tips of the points themselves to the tips of the points on the other track if the points form a crossover, or the angle or radius of curvature in the case of a branch/siding (or any other method of expressing it that makes sense, or might be more appropriate)?

 

Basically I'm thinking of what would allow a OO model train to run through a point so that it looks prototypical. I'm not sure how Hornby or other manufacturers chose 1st and second radus but I suspect that they chose something that would fit on the kitchen table and worked from there. Notwithstanding that coupling systems on rtr coachs may neither be prototypical nor close coupled, the coaches often swing wildly through lower radius points with coaches moving maybe half a coach width or more (ejecting the model passengers from the non-existent gangways).

 

As a child, I remember travelling in coaches (which I thought swung wildly at times depending on the trackwork or when approaching a terminus) but in truth the coaches may have moved a foot or a little more in relation to each other

 

I'm sure there may not be a standard size for points and that the intended speed accross the point may have dictated the dimensions (or vice versa) e.g. mainline versus siding. I have some space for the layout but I'm not sure if I have enough to recreate this.

 

Anyway, the look is what I'm after:trains:

Edited November 8, 2015 by DiveController

[jhb171achill]

Generally model points are sharper radius than prototypical ones, to save space. Real ones could vary. If you ever want to visit, say, Downpatrick, to measure / photograph, let me know by PM and I will assist in arranging it.

 

In the model world, best and most convenient results are had by using large radius ones.

[DiveController]

Generally model points are sharper radius than prototypical ones, to save space. Real ones could vary. If you ever want to visit, say, Downpatrick, to measure / photograph, let me know by PM and I will assist in arranging it.

 

In the model world, best and most convenient results are had by using large radius ones.

I'm thinking of using 'express points' where possible but I just don't have a frame of reference for the a commonly used prototype. In other words I don't know if I'd have to use 4th radius everywhere. (lot of space required)

Maybe Downpatrick whenever I get back next year which I'd try to align with a major show. If anyone is up there and wanted to take measurements without getting run over, that would be appreciated.

[jhb171achill]

When the occasion arises, DiveC, mention to me and I'll ensure you're not run over!

[Weshty]

I was querying the same thing yesterday and checked out the points at the Killarney end of Mallow. It was c.70m for the two points to allow transfer from one track to another, so each point is in or around 17".

[Glenderg]

And these guys will supply too.

http://www.marcway.net/list2.php?col=head&name=Marcway+00%2FH0+Pointwork

[DiveController]

When the occasion arises, DiveC, mention to me and I'll ensure you're not run over!

Very well, JB!

 

I was querying the same thing yesterday and checked out the points at the Killarney end of Mallow. It was c.70m for the two points to allow transfer from one track to another, so each point is in or around 17".

How serendipitous, Des! Is the point work a mainline crossover or changing roads to a platform etc. Low speed crossing?

Do you have a picture to hand or I can look for photo of Mallow online

 

And these guys will supply too.

http://www.marcway.net/list2.php?col=head&name=Marcway+00%2FH0+Pointwork

Didn't know they existed, Richie but that's some impressive point work on the page. Hope I don't need any three-way points at that price:eek: Important to know that I can't go with Code 83 (which is common over here)if I use their point work. Anyone got any experience of how well their points work? Generally Peco seems to be the gold standard

[Riversuir226]

Might be a help [ATTACH=CONFIG]20705[/ATTACH]

[ATTACH=CONFIG]20706[/ATTACH]

[Riversuir226]

[Riversuir226]

On the curve part the minimum radius is 80 meters for a yard, 115 meters for a running line and 141 meters for a hauled train. As these are the minimum a 201 needs to take a curve I presume its the minimum requirements for most of the present day network. In modelling terms unless your going to build your own or get them commissioned there isn t much to choose from. The nearest thing to them would be the long or express points offered by various companies. Setrack or small points should be avoided were possible especially when operating modern long wheelbase stock as it looks wrong.

Edited November 9, 2015 by Riversuir226

[David Holman]

With pretty much all RTR track work, as far as I'm aware, none are particularly close to prototype dimensions. Peco, for instance, has sleeper spacings that are wrong, because the track is a compromise to fit with HO as well as 00 [presumably for the USA and European markets. However, at least their medium radius points are about 900mm/3ft. Hornby's are much tighter, which is why tension lock couplings are a must - otherwise, buffer locking when propelling stock would be inevitable through reverse curves.

A 900mm radius point [technically, it should be called a turnout] in 4mm scale works out at 68.4 metres on the real thing. In old money, that is just over three chains [66 yds], which would only happen in dockyards, where there would be a check rail and the locos would have big buffers to cope. I believe that early mainline diesels were built to cope with a minimum radius of 12 chains, or well over 3 metres in 4mm scale...

So, getting prototype radii ain't going to happen unless you a blessed with enormous space. A simple oval would require the equivalent space of a double garage! In practice 900mm radii will look fine [especially compared to Hornby. Go along the self build route [eg C&L kits] and they do not talk about radii in mm, but go on A5, B5, A6, A7 etc turnouts. I've built some in 7mm scale, where [i think] a B5 equates to about 2400mm [8ft] radius. In 0 gauge, Peco points are 1800mm [6ft] radius, where aPeco point is about 450mm long, a C&L one nearer 600mm. In 4mm scale a 900mm point will be about 10 inches [250mm] long.

Overall therefore, in 4mm scale 900mm radius points will work well and look good for most purposes. Tighter radii are fine in specific circumstances like dockyards, while broader/sweeping curves will certainly enhance a mainline scene. Trouble is, few of us have the room and even if we do, the urge is always to have more layout!

By the by, the spell checker on this thing substituted g for f in the word buffers. Just as well I spotted it - though industrial engines did indeed often have big'uns...

[Junctionmad]

Dive controller.

 

I suggest you download Templot, Martin Wynnes, free track work template generator. There you can play to your hearts contents with different turnout radius and crossing angles. However few layouts can cope with prototype radius turnouts.

 

As for PECO being the gold standard , far from it. A well designed turnout hand made will out perform PECO any day, and look much better to boot , flowing track designed on TEMPLOT will always look far better akin to the prototype , then any Setrack system, which cannot properly emulate the prototype anyway. Irregular diamonds being a case in point.

 

In general the prototype didn't have 1, 2 3 or 4 th radius anything. But had flowing curves , including transition curves with turnouts integrated into such curves resulting in all sorts of radius.

 

Be aware that 00 has several track standards , the common one being 00-BF , today's that depreciated in favour of DOGA-intermediate. ( 1.25 mm Flange ways ) this is similar though not indentical to PECO geometry ( loose heeled switches were never really seen in Ireland )

 

DOGA intermediate will accept rtr wheels typically 25/110 , but other 00 track standards like DOGA-fine will have issues with these wheels

 

Also building a very large radius prototype turnout in standard 00-BF will likely cause some running issues with wheel drop. IF you ever do that you need a compromise track standard like 00-SF , which cuts the flange way gap to 1mm but narrows the track to 16.2 to allow rtr wheels to still run unmodified.

 

As you mentioned carriage end to end throw is nuts on model railways , especially crossings. Peco turnouts don't have curviform crossing vees and hence have a straight track between them when arranged as a crossover. The prototype had a transition curve flowing from one track to the other.

 

PECOs crossing vee angles are all the same which doesn't help things either. This results in changes of radius through the PECO point

 

If you built a prototype crossing with PECO geometry , all the passengers would be thrown from their seats on a crossover!

 

By the way track work is codified to REA standards which Cie by and large followed. In that regard B7 should be the smallest practical turnout in model form. Even that is very tight prototypically, min radius 30" , preferably 36"

Edited November 10, 2015 by Junctionmad

[Junctionmad]

Be aware that C & L 00 turnout kits are to DOGA-fine and will not handle rtr wheel sets without modifications

 

00 Track/wheel sets are a mine field of miscellaneous incompatible standards unfortunately

[Mayner]

As you live in the States it would probably be a better option to use NMRA track and wheel standards and use Walthers or Atlas track rather than than Peco.

 

Both systems and nearer to full size than Peco in terms of geometry & sleepers look less stubby than Peco.

 

Murphy Models, Bachmann and modern Hornby wheel profiles are based on an NMRA standard and a gauge is readily available for checking back to backs and other critical dimensions.

 

Full size point are specified in terms of switch length and crossing angle and the same principal applies regardless of gauge full size or model.

 

A HO 1:4 point is similar in overall length to a Peco medium radius point a 1:6 to Peco large radius.

 

I installed some full size point and crossing work on a narrow gauge line in the UK we found that 1:6 was the minimum for a 2-6-2T loco and bogie coaches 1:4 for 4 coupled locos and wagons.

Edited November 10, 2015 by Mayner

[Junctionmad]

OP you might find this useful http://www.clag.org.uk/protodata-bullhead.html. It refers to uk practice , but everyone except the GWR followed REA standards. GSWR/GSR Cie , would have been no different I expect

 

Note these are for bullhead track

 

This is a good read too http://www.templot.com/martweb/gs_realtrack.htm

Edited November 10, 2015 by Junctionmad

[David Holman]

Junction mad says it all far better than me, likewise Mayner!

[Glenderg]

I threw a shot of a crossover going up the gullet into CAD, and did the sums. For 00 gauge track this would need 1100mm from tip to opposite tip.

 

[DiveController]

Thanks very much for all of that, lads! Richie what's the spacing between tracks (rail to rail or centre-centre) in feet or mm OO scale?

[Glenderg]

That's scaled to 21mm track so the space is about 27mm between outside rail to outside rail. Centre to centre is about 48mm.

 

Peco express points when aligned as a crossover have 50mm centres and top to tail extend to 518mm. I think the short radius work on a track centre spacing of 67mm. R

[DiveController]

That's scaled to 21mm track so the space is about 27mm between outside rail to outside rail. Centre to centre is about 48mm.

 

Peco express points when aligned as a crossover have 50mm centres and top to tail extend to 518mm. I think the short radius work on a track centre spacing of 67mm. R

 

Thanks, Richie! A lot to assimilate form this thread but one thing's is for sure the longer the point and great the radius of curvature the better the running is going to look. Probably looking at 1:6 ratio points as much as space allows to allow visually more prototypically running over turnouts.

[Junctionmad]

if you do the tests , with current models you tend to find that anything below B7 is getting close to train set curves. in fact my tests suggest that even B7 makes it impossible to propel across crossovers and avoid buffer lock, particularly with non tension lock coupling that rely on the buffers, like Digham couplings. ( and I suspect is also true for Spratt and Winkle and AJ couplings too.

 

There is definitely a space advantage in hand built turnouts over PECO, in that entry and exit track can be shortened to the min possible, so that a B7 can fit in the space of an equivalent PECO , but with better radius

 

It exacerbated on bogies vehicles with excessive end throw.

 

theres no easy answer unless you have oodles of space and therefore money

[David Holman]

Re hand made v commercial track, the middle ground is occupied by the likes of Marcway. Arigna uses their points, which can be very comparable in price to PECO if you buy off the shelf, though custom made is around 50% more.

One particularly useful version in 7mm scale is their 6' radius Y point. From toe to clearance is just 12"/30cm. Would imagine the 00 version offers similar economy of space. A standand PECO Y in 7 mm is half as long again...

Marcway points are copperclad construction and self isolating, so if you use wire in tube control, no additional switching is required.