Peco OO/HO large radius point measurement query

[rue_d_etropal]

As I have a maths degree, I think I should be able to calculate angles and lengths, but I am getting frustrated with Peco Streamline large radius OO/HO point.
According to info online it is to a nominal 1524mm(60in) radius, with an angle of 12 degrees.
This would then give a length from toe to end of curve of 317mm(12.5n approx),calculated from radius times sin of angle, but actual length is 253mm (9.97in) . This happens to be the value if the radius is 1219mm(48in).
So what is the radius?

[kevinlms]

Don't know, but Peco have this to say about their points.

 

http://www.peco-uk.com/page.asp?id=radius

 

Which of course, doesn't answer your question!

[BR60103]

I think it depends on whether you are looking at the limiting curve radius (for rolling stock) or the substitution radius (what curve can I drop it in?) There are a couple of straight bits at the end.

[Joseph_Pestell]

Don't know, but Peco have this to say about their points.

 

http://www.peco-uk.com/page.asp?id=radius

 

Which of course, doesn't answer your question!

 

Not only does it not answer the question, it is in direct contradiction with Simon's calculation. He makes it to be a 4' average (therefore much less at some point between the straight bits) whereas Peco make it to be a 5' average.

 

I'll go and get my calculator.

 

Edit: I have done the calculation in a slightly different way. 12 degrees is 1/30th of a circle. A 30th of a circle of 60" radius is 12.58 inches. So Peco's "average" is wrong - very wrong.

[The Bigbee Line]

I'm sure the great and the good will comment on this one.

These points are a geometric fudge. Different lengths, all with the same crossing angle.

Useful to join them together, but not like the prototype.

If you can tolerate the U.S. Sleeper sizes. The HO code 83 are better from a geometry point of view.

If you want to stick to code 75 or code 100, I think the medium point is the best proportioned.

[rue_d_etropal]

The Peco track geometry might be a fudge, but the large radius point so close to being a proper curve, that it makes no difference. Maybe a series of straights, but no straight at either end, whereas the medium and short ones do have sections of straight at end of curve.

Sad as it might sound , I have investigated (researched?) model railway track geometry, and found some surprising coincidences. Much dates back to track Hornby Dublo produced, and how they progressed from 15in radius to 17 and a bit inches, based on combinations of angles  and track centre to centres they wanted to use. To get some geometry to work, some model track systems put in fudges. The Peco medium radius crossing (marketed as Setrack) is a bit of a fudge, and I have found it odd they did not follow others and do left and right handed versions.

There has been debate on what the correct gap there should be between parallel tracks, and it does seem to be a bit of coincidence that using 4ft radius and an angle of 12 degrees, both simple measurements, that this comes out at what is used as a standard within the Peco range. Remember everything is a compromise, so one compromise standard is as good as any other, just as long as you keep to those standards. The thing about any modular system(and that is what these model track systems are) , is that they have to work together, and the simpler they fit together the better for the hobby.

Something else, for those that are concerned about rail profile, is that within the OO and HO scale boundaries, Peco produce rail to code 70, code75, code 80, code 63 and code 100. Some of these are shared with other scales, but that is a big range, much of it being for relatively small markets, although I suspect the USA market is big for code 70 and code 83, otherwise Peco would have not made the investment.

[Godders]

As I have a maths degree, I think I should be able to calculate angles and lengths, but I am getting frustrated with Peco Streamline large radius OO/HO point.

According to info online it is to a nominal 1524mm(60in) radius, with an angle of 12 degrees.

This would then give a length from toe to end of curve of 317mm(12.5n approx),calculated from radius times sin of angle, but actual length is 253mm (9.97in) . This happens to be the value if the radius is 1219mm(48in).

So what is the radius?

 

Hi "Rue"

 

I hope I don't offend by abbreviating your name. You may find it helps your understanding of the Peco range and geometry if you were to download "Templot" by Martin Wynne.

 

templot allows you to analyse and synthesise track. martin has a creation of the Peco Large Radius Turnout, with the software you can overlay curve, extend rails, look at the type of crossing vee, regular, curviform whatever. I have my opinions on Peco track, some good, some not so good but use of Templot will allow you to make your own conclusions. 

 

Hope it helps.

 

PS Being nosey why do you need/want to know this info?

 

Cheers Godders

[hayfield]

As I have a maths degree, I think I should be able to calculate angles and lengths, but I am getting frustrated with Peco Streamline large radius OO/HO point.

According to info online it is to a nominal 1524mm(60in) radius, with an angle of 12 degrees.

This would then give a length from toe to end of curve of 317mm(12.5n approx),calculated from radius times sin of angle, but actual length is 253mm (9.97in) . This happens to be the value if the radius is 1219mm(48in).

So what is the radius?

 

 

There are several radii that could be quoted as a turnout is a series of straights/angles and curves. However Peco use the same crossing angle in their turnouts and change the radii buy using different switch angles and (I assume) curves.

 

If following prototype practice you would alter both switch size and or crossing angle. Maths does come into it but the starting point is the ability to join it to other turnouts or crossings

[Joseph_Pestell]

This subject came up quite a bit in the discussion on modular standards. One of the conclusions was that the Peco slip points should not be used on running lines (except where a single slip forms part of a trailing crossover). It was taken as read that the nominally "medium" radius slips in fact have a curve radius of about 24".

 

Following Simon's post, I am wondering if they may not even be a bit tighter than that but I have not got one to hand to measure.

[Ravenser]

The Peco track geometry might be a fudge, but the large radius point so close to being a proper curve, that it makes no difference. Maybe a series of straights, but no straight at either end, whereas the medium and short ones do have sections of straight at end of curve.

Sad as it might sound , I have investigated (researched?) model railway track geometry, and found some surprising coincidences. Much dates back to track Hornby Dublo produced, and how they progressed from 15in radius to 17 and a bit inches, based on combinations of angles  and track centre to centres they wanted to use. To get some geometry to work, some model track systems put in fudges. The Peco medium radius crossing (marketed as Setrack) is a bit of a fudge, and I have found it odd they did not follow others and do left and right handed versions.

There has been debate on what the correct gap there should be between parallel tracks, and it does seem to be a bit of coincidence that using 4ft radius and an angle of 12 degrees, both simple measurements, that this comes out at what is used as a standard within the Peco range. Remember everything is a compromise, so one compromise standard is as good as any other, just as long as you keep to those standards. The thing about any modular system(and that is what these model track systems are) , is that they have to work together, and the simpler they fit together the better for the hobby.

Something else, for those that are concerned about rail profile, is that within the OO and HO scale boundaries, Peco produce rail to code 70, code75, code 80, code 63 and code 100. Some of these are shared with other scales, but that is a big range, much of it being for relatively small markets, although I suspect the USA market is big for code 70 and code 83, otherwise Peco would have not made the investment.

 

 

I agree that Peco have too many 16.5mm gauge ranges, and this probably needs addressing by them. However I'm unclear about the rail profiles you list. Code83 is the new US NMRA-track standard compliant range. Code 100 we know , and it comes in 3 flavours : Setrack (deadfrog to code 100 and train set geometry with (traditionally) rather coarser track standards than Streamline) , and Streamline 100 , in both deadfrog and live frog versions. Streamline code 75 comes in live frog only. 

 

But I don't recognise code 70 and code 80 in their ranges? I haven't investigated their O-16.5 range but I've always assumed the standards mirrored Streamline100, since they would need to cope with the cheap Hornby 0-4-0 ands 0-6-0 chassis often used by 7mm modellers

 

To my mind, the logical rationalisation for the future would be to withdraw code 100 live frog as the tooling wears out, tighten up the flangeways on code75 to suit modern RTR, integrate Streamline Code 100 with Setrack and present the buyer with 2 ranges : code 100 coarse /deadfrog for legacy stock and code 75 live frog with a finer rail and a finer standard for the more sophisticated end of the market.

 

At the moment there is little differentiation amongst all the ranges

[Ravenser]

This subject came up quite a bit in the discussion on modular standards. One of the conclusions was that the Peco slip points should not be used on running lines (except where a single slip forms part of a trailing crossover). It was taken as read that the nominally "medium" radius slips in fact have a curve radius of about 24".

 

Following Simon's post, I am wondering if they may not even be a bit tighter than that but I have not got one to hand to measure.

 

They are certainly very tight by handbuilt standards - the issue being the short length of the switchblades. That said, when I was involved with a continuous run club layout , we had a slip at each end of the fiddle yard and a full circuit involved taking the curved route through the slip. When we got silly , we used to send Pendolinos and Voyagers round at full tilt or near it , and they went through the curved route of the slips without derailing. I think we were a bit hesitant about giving it speed step 128  through the slip , but speed step 110-115 certainly

[Silver Sidelines]

The Peco Code 100 medium radius single slip is a much tighter radius than the rest of the range of Peco Medium radius points.  I know this because the singe slip will not accept a lot of my close coupled Bachmann engine/tenders that will traverse the other points.  I have posted this video elsewhere but it highlights the very abrupt turn at the single slip and you can see the Bachmann 4MT hesitate to overcome the extra friction.  I installed the single slip to replace a diamond with plastic frogs - there is more metal in the single slip and when used as a diamond crossing the running quality is excellent.

 

Ray

[rue_d_etropal]

When I said OO/HO scale I was meaning the scale not the gauge.As a mathematician, one thing that does get me annoyed is confusing scale and gauge. Having said that, I am stretching it by saying OO scale, but thanks to what happened just over 100 years ago we are stuck with mixed up terminology. OO scale rolls off the tongue easier than 4mm scale or 1/76 scale and encapsulates a lot in those two words.

Code 80 is used in OO9 track, and code 70 is used in the HO3(?) which I think is 10.5mm gauge. I am interested and model in various scales and gauges, probably more than most in the hobby, so tend to look towards the boundaries and am prepared to question things. I would rather be a thinker than a sheep, and enjoy a challenge.

 

One thing Peco are experimenting with is the unifrog, which can be set to dead or live, and if it is successful then I think that may replace some of current frog designs. Sorry to say I am a die-hard 'dead frog' modeller, as I personally have found (over 40 years modelling) that it is more reliable and easier to use, especially when I wire them so not dependent on power going through point blades. The Peco points if you look closely are designed to be wired up this way(slot in sleeper under rails), in a similar way to some continental trackwork.

One thing I would like to see is a sprung point blade option, especially as it is now used quite a bit on real railways. Even something like the PL12 point motor base, which could be fitted onto points would be acceptable(remembering to remove locking from point blades). It is something I have experimented with myself and it can work.

 

As for the single slip, I think that is actually 610mm(2ft) radius so is not a medium radius point. Trouble is that, given my original question, I now feel ihave to double check each point to see if the stated radius is correct. It does puzzle me that  these measurements are not on the point template drawings, but are on various advertising info.

[shortliner]

Simon - I'm not questioning your knowledge of mathematics, but the turnout angles shown by you in your first post  do not appear to agree with these   http://www.peco-uk.com/prodtype.asp?strParents=3309,3322&CAT_ID=3327&numRecordPosition=1

[Ravenser]

When I said OO/HO scale I was meaning the scale not the gauge.As a mathematician, one thing that does get me annoyed is confusing scale and gauge. Having said that, I am stretching it by saying OO scale, but thanks to what happened just over 100 years ago we are stuck with mixed up terminology. OO scale rolls off the tongue easier than 4mm scale or 1/76 scale and encapsulates a lot in those two words.

Code 80 is used in OO9 track, and code 70 is used in the HO3(?) which I think is 10.5mm gauge. I am interested and model in various scales and gauges, probably more than most in the hobby, so tend to look towards the boundaries and am prepared to question things. I would rather be a thinker than a sheep, and enjoy a challenge.

 

One thing Peco are experimenting with is the unifrog, which can be set to dead or live, and if it is successful then I think that may replace some of current frog designs. Sorry to say I am a die-hard 'dead frog' modeller, as I personally have found (over 40 years modelling) that it is more reliable and easier to use, especially when I wire them so not dependent on power going through point blades. The Peco points if you look closely are designed to be wired up this way(slot in sleeper under rails), in a similar way to some continental trackwork.

One thing I would like to see is a sprung point blade option, especially as it is now used quite a bit on real railways. Even something like the PL12 point motor base, which could be fitted onto points would be acceptable(remembering to remove locking from point blades). It is something I have experimented with myself and it can work.

 

As for the single slip, I think that is actually 610mm(2ft) radius so is not a medium radius point. Trouble is that, given my original question, I now feel ihave to double check each point to see if the stated radius is correct. It does puzzle me that  these measurements are not on the point template drawings, but are on various advertising info.

 

I think the 12mm gauge range is only going to be bought by HOm modellers (Swiss particularly) and 3mm scale modellers - I've seen a couple of 3mm scale layouts where it's been used, and if I ever build a 3mm scale layout it will probably use the HOm points. OOn3 seems to be a very minor interest

 

OO9 track is effectively a flavour of N gauge - and the traditional N gauge streamline uses code 80. Not surprising if Peco use the same for OO9. Looked at that way , the number of rail sections being used makes more sense

 

I've always wired Peco live-frogs to a switch drive driven by the point motor : that eliminates the problems caused by unreliable contact of the switxh blades

[rue_d_etropal]

Shortliner, I noticed that, but those are the code 83 points, using USA geometry. The Peco web page is a bit mixed up, with the different 16.5mm gauge points is an almost random sequence. Looks like a typical database search type listing.

 

Ravenser, I find your attitude to other scales and gauges a bit odd, but sadly typical of how some in the hobby feel. I have come across a few people who think that OO9 is same as N gauge, but I don't think it should be passed over like that, especially as Peco are now leading the way to renewed interest in it, and have worked with both Minitrains and Bachmann on using Peco designs, and Heljan to produce new locos.

I had forgotten about the 12mm gauge track. Not much on Peco site, so looked at Gaugemaster, and the HOn3 is code 70, but does not say for the HOm. I thought the HOm was code 75 but it easily be code 83.

[Grovenor]

However Peco use the same crossing angle in their turnouts and change the radii by using different switch angles and (I assume) curves.

This is something of a misconception, it is not the crossing angle which is standard at 12 degrees with the Peco points, its actually the angle of divergence at the end of the turnout. This is only the same as the crossing angle for the small radius turnout, the medium and long have curved vees which results in the crossing angle being less than the 12 degree divergence angle.

As best as I can estimate from the templates, the small radius has a crossing angle of 12 degrees, close to 1:4.75, the medium radius crossing angle close to 1:5.5 and the large radius 1:6.75

[RichardS]

I think you will find that the 'substitution radius' or the External Geometric Radius of all but one Peco Streamline Code 100/75 1/87 scale points is the same, and this is because the angle is the same at 12 degrees. The radius is 1162.34 mm. The exception is the small Y which is 24 degrees and has a SR of 293.81.

 

I haven't noticed the 'curved Vs' that Grovenor mentioned but will have a closer look.

 

The 'toe chop' (that's the straight bit) on all three straight points and the curved is 13.77 mm to the best of my knowledge.

 

The official (confirmed by PECO technical desk when I asked) track separation of streamline code 100/75 is 2 inches or 50.8mm.

 

Nominal radii are quoted because the radii within the points themselves varies through its length I understand.

 

For interest, I am presently assisting with the build of a large OO layout for a colleague who uses three link couplings on his mainly kit-built stock. Buffer lock occurs on the inside of the curved points(30" nominal) but wagons will travel through the medium radius points (30"). Obviously if you use tension lock or kadees then anything will go through anything as on rtr these are designed for second radius which is something like 17.5 inches. 

 

To be frank the issues of PECO track have been discussed so frequently that if you are using RTR stock on 16.5mm you'd be better off enjoying your hobby rather than worrying about angles and geometries. PECO track works as evidenced by the 000's of layouts using it. Sometimes it's better to just accept things as they are.

 

If you really do want to know about track geometries have a look at the Templot and Hand Built Track forums under the special interest group section and the OO-SF and DOGA debates elsewhere on RMWeb. You won't sleep if you do.

 

 

  

 

 

 

[RichardS]

Incidentally, the 12 degree arc of the substitution radius is 243.44 mm.

[Crewlisle]

 

 

To be frank the issues of PECO track have been discussed so frequently that if you are using RTR stock on 16.5mm you'd be better off enjoying your hobby rather than worrying about angles and geometries. PECO track works as evidenced by the 000's of layouts using it. Sometimes it's better to just accept things as they are.

 

 

The most common sense comment made on this forum!

[Grovenor]

 

 

I think you will find that the 'substitution radius' or the External Geometric Radius of all but one Peco Streamline Code 100/75 1/87 scale points is the same, and this is because the angle is the same at 12 degrees. The radius is 1162.34 mm.

I think you need to do a refresh on your geometry, all the three 12 degree points have a different substitution radius as, although the angle is the same the arc length is different,

turning through 12 degrees in 185mm needs a much smaller radius than turning 12 degrees in 259 mm.

regards

[RichardS]

Keith (Grovenor) I presently disagree. I used a formula to calculate the figure. It was online but I cannot find it at the moment. It's getting late! I also tested the result in practice with real points.

 

I also refer you to this thread

http://rmweb.co.uk/forum/viewtopic.php?f=5&t=32026

and Martin's comment.

 

I note you haven't actually quoted what the substitution radii are for the different points. Please could share the results you have and the formula you used to calculate the substitution radii of PECO points?

 

I'm also a little puzzled how two straight points with different substitution radii might join on a cross over and maintain the specified and desired track separation.

 

If I'm wrong I​'ll happily correct my assertion. I am always willing to learn. :-)

​

[RichardS]

Sorry Keith one other point, the length of the point you quote is surely the length of the straight leg, ie a section of the tangent, not the length of the arc? Correct me if I am wrong please?

[kevinlms]

This is something of a misconception, it is not the crossing angle which is standard at 12 degrees with the Peco points, its actually the angle of divergence at the end of the turnout. This is only the same as the crossing angle for the small radius turnout, the medium and long have curved vees which results in the crossing angle being less than the 12 degree divergence angle.

As best as I can estimate from the templates, the small radius has a crossing angle of 12 degrees, close to 1:4.75, the medium radius crossing angle close to 1:5.5 and the large radius 1:6.75

Agreed, it is the end of the point that is where the 12 degrees is set & thus explains why the short points are much tighter than the medium (same 12 degrees but in a shorter length) & why the large ones are more generous (same 12 degrees in a longer length). It doesn't take mathematics to work this out, as it is obvious.

 

The slip points are different, because they are more compact, but in the same 'envelope', as is the 3 way points & curved points. All should be much longer, if the aim was to have similar minimum radius within each piece. Peco made the decision, to make all these to fit their modular construction, instead. The result is that they are tighter, which should be equally obvious.

 

The question is what to do about it.

 

1/ Only use standard points. If 'special' points are required, build your own.

2/ Buy another product.

3/ Build your own.

4/ Use Peco intelligently, using them within their limitations.

 

There is always this option.

 

5/ Pick another hobby, that has one set of standards, without compromises - any such thing?

[martin_wynne]

As I have a maths degree, I think I should be able to calculate angles and lengths, but I am getting frustrated with Peco Streamline large radius 00/H0 point.

 

Hi Simon,

 

The information provided by Peco is written in marketing-speak. You won't be able to make sense of it by mathematics.

 

All Peco turnouts have an exit angle of 12 degrees at 1 inch (25.4mm) offset.

 

This means that all turnout sizes have the same substitution radius of 1162.24mm  ( 45.76 inches ).

 

However the smaller sizes will need some additional approach track to reach the tangency point. On the other hand the large size turnout requires a bit chopped off to meet tangency.

 

I have posted a detailed explanation of these turnouts on RMweb several times, see for example: http://www.rmweb.co.uk/community/index.php?/topic/71956-correct-nominal-radius-of-00ho-code-100-peco-large-radius-turn-out/&do=findComment&comment=1047844

 

 

This screenshot shows plain track at the substitution radius aligned over the turnout:

 

 

 

 

Download Templot (free to use) from: http://85a.co.uk/forum/view_postx.php?post_id=10771

 

Download the above file from: http://85a.co.uk/forum/view_topic.php?id=294&forum_id=10

 

Load it into Templot and then expand the information panel.

 

Here is a copy of the info. Note that the design includes a 1:35 custom straight switch which is not recommended for any other use.

 

The crossing angle is 1 in 5.93 RAM  ( 1 in 5.97 CLM ) curviform.

 

template generated at 00:42:42 on 14/09/2015 using Templot v:2.11.b

scale = 4.0 mm/ft     scale ratio = 1:76.2

track gauge = 16.5    flangeway gap = 1.5

template: straight

rail head only (bullhead): rails vertical

------------

LH turnout:

 1:35 Peco-only left-hand switch (unjoggled)

1 in 5.93 RAM  ( 1 in 5.97 CLM ) curviform V-crossing

square-on timbering

------------

adjacent track centres main side = 50.8

adjacent track centres turnout side = 50.8

angle at TXP crossover mid-point (CTRL-5) = 12.0 degrees ( 1 in 4.7 RAM )

angle at TVJP turnout road vee joint (CTRL-6) = 12.0 degrees ( 1 in 4.7 RAM )

------------

overall length = 258.0

approach/exit track in  45 ft rails / 19 sleepers per length ( rail length = 180.0 ):

approach track length = 0

exit track length = 0

 

turnout-road centre-line radius (at turnout-curve) = 1137.88

 

nominal switch-curve radius (rail gauge-face) = 2940.0  (straight switch)

turnout-curve radius (rail gauge-face) = 1146.13

switch-curve radial centre: X = [ -2855783.26 ]  Y = 99954211.68  (from CTRL-0)

turnout-curve radial centre: X = 18.83  Y = 1138.41  (from CTRL-0)

 

switch front (rail-joint to switch-toe) = 16.57

virtual lead (switch-toe to fine-point) = 192.92

actual lead (switch-toe to blunt nose) = 194.41

blunt nose to timber A = [ -0.65 ]

width of blunt nose = 0.25

 

wing rail reach length (main-side) = 18.0

wing rail reach length (turnout-side) = 18.0

check rail overall length (main-side) = 40.0

check rail overall length (turnout-side) = 40.0

------------

smallest radius on this template = 1138 mm ( 44.8 " )

total angular swing on this template = 0 degrees (in main road)

------------

nominal gauge :   00/H0    16.5  mm    4 mm/ft     1:76.2    00-Universal UK         

------------

template location on trackpad :

 

rotation :  X = 0   Y = 24.0   K = 0 degrees

   shift :  X = 0   Y = 0

rail-end :  X = 0   Y = 24.0

 

peg from origin :  X = 0   Y = 32.25   K = 0 degrees

peg from notch :  X = 0   Y = 32.25   K = 0 degrees

 

 

track centre-line radius at peg = straight  ( 3936811.02 " )

internal geometrical radius = 1176.1  ( 46.3 " )

external geometrical radius (substitution radius) = 1162.24  ( 45.76 " )

------------

 

p.s. Simon, the overall length is 258mm, not 253mm, see:   http://www.peco-uk.com/product.asp?strParents=3309,3322&CAT_ID=3327&P_ID=17448

 

regards,

 

Martin.