Peco Turnout Angles

[hayfield]

13 hours ago, Wheatley said:

You still don't need an engineering drawing for that.

 

 

If you join Templot club and have Templot you can easily make your own building templates,  if you are polite and ask nicely there are a few who have made some already and might be willing to share them. They are cheap enough to buy new or especially second hand !!

 

Having said this why would you want to build ? one especially if you are an engineer 

Edited January 23, 2021 by hayfield

[ejstubbs]

4 hours ago, kevinlms said:

When railway companies had a contractor build a batch of locomotives, they generally came with a full set of plans.

 

rab wrote "restricted as much as possible".  That certainly doesn't rule out a contractor being contractually obliged to provide a full set of engineering drawings of the thing they're building, but it doesn't mean that the LMS or the North British would have happily made copies of the drawings for a Royal Scot available to all and sundry on whatever the nearest equivalent of the world wide web was back in the 1920s.

 

I believe there are historical examples of railway companies making their designs, or parts of their designs, available to other companies but that would undoubtedly have been under some form of commercial arrangement (even if no money actually changed hands) which would almost certainly have included what we now call an NDA.  Then there's stuff that was patented, and licensed by the original designer for others to use, and of course whatever people could glean from the various professional journals.  But that latter would be a case of designing your own version of the published idea, a journal article wouldn't include drawings of sufficient detail to hand straight over to a workshop or factory in order to get an exact replica made.

[rab]

5 hours ago, kevinlms said:

Strange, but that isn't entirely true of steam locomotive manufacturers in the UK.

 

When railway companies had a contractor build a batch of locomotives, they generally came with a full set of plans. It was quite common for the railway company, once they were not snowed under with work, build some more examples themselves.

 

The LMS had a good example, in that the original 50 Royal Scots were built by North British. Later they built another 20 at Derby. They certainly didn't 'reverse engineer' the plans, they built them to the supplied plans from North British.

 

On occasion, a railway company would go to another contractor, to get more examples built, using the same plans, sometimes with alterations/improvements, in light of operating experience.

 

Agree, that was why I said 'as much as possible '.

 

Yes we used contractors, a lot, so had to issue drawings to them,

but there was always a concern they might be used

in the wrong way and or by the wrong people.

 

This was especially the case when we started using Chinese toolmakers!

Edited January 23, 2021 by rab

[kevinlms]

2 hours ago, rab said:

Agree, that was why I said 'as much as possible '.

 

Yes we used contractors, a lot, so had to issue drawings to them,

but there was always a concern they might be used

in the wrong way and or by the wrong people.

 

This was especially the case when we started using Chinese toolmakers!

Ah yes, a late engineer friend of mine was sent to Hong Kong decades ago, to see about getting stuff made.

 

It was of great concern to him, when someone opened the door to the factory and it seemed to him that a lot of stuff was going out in unmarked boxes!

[Budgie]

On 22/01/2021 at 01:10, Pacific231G said:

In the 1970s I built a North American H0 layout but that was the first time I ever encountered frog numbers and I'd never heard or read about any modellers using crossing angles for British prototypes, Even though I was building some of my own #6 turnouts using NMRA gauges I think I assumed that the use of crossing angles rather than radii simply reflected the different geometry of American pointwork. It certainly looked different.   

 

As I understand it, the first time crossing angles were applied to British track was in the Protofour series of articles in the Model Railway Constructor in the 1960s.

[Pacific231G]

3 hours ago, Budgie said:

 

As I understand it, the first time crossing angles were applied to British track was in the Protofour series of articles in the Model Railway Constructor in the 1960s.

Interesting. I read some of those articles a few months ago. They seemed to think that the best way to get better runninng in 4mm scale was to reduce absolutely everything to scale. It struck me then, that if that were true ,narrow gauge track and wheel standards would simply be scaled down versions of those for standard gauge but a glance at any N.G. railway shows that not to be how it's done.

 

I've just found, in one of my old files, a 1970 track catalogue from De Dietrich's Reichshoffen factory  from 1970 that includes  specs. for various standard "SNCF old model" turnouts and slips, as well as  a catch point. I assume they were supplying these to various railways as the specs are very detailed and they give both the crossing angle and the radii. as well as lengths, and details of timbering, described as traverses (sleepers) and pieces de bois (timbers?).

 

Crossing angles are given as tangents (the inverse of crossing ratio though based on right angle rather than isosceles triangles which makes some difference)

As well as the switch rail  and turnout radii (the same in some turnouts) they also give the gauges at various key places. which range from 1437 mm up to to 1455 through the diverging switch and crossing for the sharpest turnout. 

For a tg. 0167 turnout, the sharpest and AFAIK equivalent to a 1: 6 crossing, the radii given are 150m and 140m for the switch panel and 140m for the intermediate track. 

That would be an unusally sharp point and the sharpest I know of used on passenger running lines (but at slow speeds) was tg. 013 (crossing angle 1:7.5) which came in long, short and extra short varieties but would normally have been confined to siding. The two other standard crossing angles were tg. 0.11 (1:9) and tg. 0.10 (1:10)  These don't include higher speed turnouts and, so far as I'm aware, SNCF itself dropped the tg. 0.167 crossing except for the Y points used in marshalling and shunting yards. 

Compared with Germany and America. I think French pw practice was always very much closer to British even to the use of chaired bullhead track so I'd be interested to know if and how much their design of pointwork differed.

 

[ClikC]

50 minutes ago, Pacific231G said:

Interesting. I read some of those articles a few months ago. They seemed to think that the best way to get better runninng in 4mm scale was to reduce absolutely everything to scale. It struck me then, that if that were true ,narrow gauge track and wheel standards would simply be scaled down versions of those for standard gauge but a glance at any N.G. railway shows that not to be how it's done..

I’m not aware of any published NG wheel and rail standards, but I suspect any deviation from the standard gauge system, will significantly less than the deviation of course scale 00 of the 1960’s is to the P4/S4 standards developed by the Model Railway Study Group. Unless said NG railway is also running with rigid wheelbases.

 

I’ll drop a video of the Colin Craig FFA/FGA testing on Mostyn here, and leave my arguments at that.

 

https://youtu.be/s7KHkp0oJd4

Regards

 

 

[Pacific231G]

5 hours ago, ClikC said:

I’m not aware of any published NG wheel and rail standards, but I suspect any deviation from the standard gauge system, will significantly less than the deviation of course scale 00 of the 1960’s is to the P4/S4 standards developed by the Model Railway Study Group. Unless said NG railway is also running with rigid wheelbases.

 

I’ll drop a video of the Colin Craig FFA/FGA testing on Mostyn here, and leave my arguments at that.

 

https://youtu.be/s7KHkp0oJd4

Regards

 

 

 

The point I was trying to make is that an NG railway doesn't generally have a proportionally smaller  flange depth, crossing clearance and tyre width compared with standard gauge and, at least in the larger narrow gauges,  these may very well be the same. It's not simply a scaled down version of SG and narrow gauge railways don't therefore need ever finer tolerances as the gauge reduces.

The argument for using P4/S4 is surely one of scale accuracy and appearance. With very fine tolerances and compensation, it demonstrably is possible to get scale wheels to run entirely satisfactorily on scale track. The video of Mostyn demonstrates that. The coarser standards typically used do enable vehicles to run without compensation but at the cost of realism. The use of compensated wheel bases can though help with any track and wheel standards as Peter Denny and others proved seventy years ago. The compensation is not though simply a scale version of the suspension used by full sized railways and couldn't be since physical variables don't scale at the same rate. 

I'm certainly not saying that the P4/S4 standards (or P87 come to that) are misguided; for those able to work to very fine tolerances they are fine and look more like the real thing. It was the assertion, made by at least one member of the MRSG, that simply scaling everything down from full size was the only way to achieve really good running that didn't make sense.

 

The best running I've ever had was from track and wheels to NMRA standards because, though far coarser thn P87, the wheel profiles and track wer matched. Derailments were very rare and wheels went through pointwork smoothly with the tyres properly supported through frogs (V crossings) 

 

I think I do have some wheel and track standards for metre gauge somewhere but I'd have to dig them out.

Edited January 25, 2021 by Pacific231G

[rab]

I notice that bebbspoke has gone rather quiet on this subject.

Perhaps they're busy counting rivets on the models

Edited January 25, 2021 by rab

[hayfield]

1 hour ago, rab said:

I notice that bebbspoke has gone rather quiet on this subject.

Perhaps they're busy counting rivets on the models

 

You frightened him off !!

 

[Pacific231G]

On 25/01/2021 at 11:49, hayfield said:

 

You frightened him off !!

 

I did wonder if he was just trolling but decided to give him the benefit of the doubt. His three posts in this topic are the only ones he's made to RMWEB though he's been registered for about a year.

[tynewydd]

Just a note to add to this discussion that the latest version of XTrackCAD V5,2 (multi-platform and free as always) has adjusted several Peco OO and N turnouts/points based on the good graces of the technical bureau at Peco.
 

The turnout dimensions were corrected for curved, three way and Y points. XTrackCAD does not aim for precision within the point but does for the external offsets, angles and radii so that the overall design fits together as it will when laying the real track. Our files will not help attempts to copy internals by others as we did not obtain or model those details.

 

I would say that Peco has been much more open to providing this level of information than other manufacturers we asked.  We previously found that trying to accurately measure exact dimensions from the PDF templates available from Peco website was very hard especially for end radii and angles on these more complex types.  We also had some suspicion that the PDFs and the products might have diverged very slightly over time as the molds were repeatedly retooled and replaced and improvements made to enhance running.
 

Adam

[DCB]

On 27/01/2021 at 12:11, Pacific231G said:

I did wonder if he was just trolling but decided to give him the benefit of the doubt. His three posts in this topic are the only ones he's made to RMWEB though he's been registered for about a year.

He made a valuable contribution and made me think about "Playing Trains" which led to me clearing the snow off the outside branch at the weekend by repeatedly ramming it with 2  X  OO pannier tanks coupled together, a Gaiety and Farish.  Great fun.  Oh well back to the serious stuff of cutting up OXO tins and counting rivets as I try t build a B16/2 before Hornby make one. 

[Pacific231G]

Something I have been wondering about Peco's geometry is the extent to which it incorporates a degree of transtion through the diverging stock and closure rails. As I understand it, full size turnouts, apart from high speed one, don't do that as the speeds through them would be very low. My reading of PW textbooks is that there are essentially two main radii, the switch radius and the turnout radius. If those radii are the same then it's a "natural" turnout. For  junction points with curved crossings (as with Peco's large radius points) the turnout radius continues through and beyond the V crossing.  Incorporating transition's in point work is somethng that Peter Denny also referred to in his book.

It would make sense to do that for model pointwork since we tend to regard a no. 6 crossing as suitable for main line pointwork taken at speed and a number 5 as a good standard point. 

Edited January 29, 2021 by Pacific231G

[AndyID]

On 24/01/2021 at 17:19, Pacific231G said:

 

 It was the assertion, made by at least one member of the MRSG, that simply scaling everything down from full size was the only way to achieve really good running that didn't make sense.

 

I agree with you. Nothing in engineering is ever as simple as just scaling everything down, and that applies to electronic engineering too. You can scale the dimensions but you can't scale the underlying physics.

 

My personal favorite is coning wheels. It might be worth it for the cosmetic effect but it's a complete waste of time on small scale models. In fact it actually makes them run worse rather than better.

 

(I'm donning my flak jacket now )

[tynewydd]

15 hours ago, Pacific231G said:

Something I have been wondering about Peco's geometry is the extent to which it incorporates a degree of transtion through the diverging stock and closure rails. As I understand it, full size turnouts, apart from high speed one, don't do that as the speeds through them would be very low. My reading of PW textbooks is that there are essentially two main radii, the switch radius and the turnout radius. If those radii are the same then it's a "natural" turnout. For  junction points with curved crossings (as with Peco's large radius points) the turnout radius continues through and beyond the V crossing.  Incorporating transition's in point work is somethng that Peter Denny also referred to in his book.

It would make sense to do that for model pointwork since we tend to regard a no. 6 crossing as suitable for main line pointwork taken at speed and a number 5 as a good standard point. 

It is certainly true that the Peco track shapes are often both compound curves and incorporate transitions to "fit it all together". Peco explained as much when we were discussing the dimensions with them. 

The XTrackCAD V5.2 upgraded "turnout builder" tool that we use to create the track templates incorporates a Cornu curve fitting engine -> which does the heavy lifting to use the mathematical family of curves from which railway easement/transitions come.  We also use the engine to solve for these conditions in real time while users dynamically join their tracks together with transitions/easements as the user drag the ends or move additional "track pin" constraints along the desired track path.  The externals (positions, angles, and centers and radii) of the points are fed in and the resulting track curves are smooth transitions between them.  This is not to say that our curve solution for a turnout is the one Peco used of course, which is why we don't claim that the internals are identical, but it is the smoothest curve achievable with a linearly varying curvature given the end constraints. 

 

I'm sure that the Rev PD method of laying out his station throats and so on allowed him to achieve superior results because his track lines would all be smooth curves throughout the frogs and switch blades. The scratch track builder has the advantage of a fully customizable solution. This degree of design freedom, as I understand it from the excellent help material at Templot, would have been uncommon in much of the prototype because the trackwork was usually assembled in parts from sets of stock items that each had fixed geometry rather than being fully "bespoke".  But the real thing was also not anywhere as compressed as the typical layout, allowing for much more languid curves - even accounting for scale - in which the inserted fixed elements would prove much less of a "jolt" anyway. 
 

[hayfield]

16 hours ago, Pacific231G said:

Something I have been wondering about Peco's geometry is the extent to which it incorporates a degree of transtion through the diverging stock and closure rails. As I understand it, full size turnouts, apart from high speed one, don't do that as the speeds through them would be very low. My reading of PW textbooks is that there are essentially two main radii, the switch radius and the turnout radius. If those radii are the same then it's a "natural" turnout. For  junction points with curved crossings (as with Peco's large radius points) the turnout radius continues through and beyond the V crossing.  Incorporating transition's in point work is somethng that Peter Denny also referred to in his book.

It would make sense to do that for model pointwork since we tend to regard a no. 6 crossing as suitable for main line pointwork taken at speed and a number 5 as a good standard point. 

 

David

 

The whole idea of Peco's turnouts and crossings is not to provide a prototypical look or performance, in fact quite the contrary

 

Very cleverly they have produced an interchangeable system of turnouts and crossings of differing sizes which are very easy to use and most of all work very well. In fact it is so good at what it does its customers are very happy to turn a blind eye to it being under scale (as its an H0 system) and its looks, But Peco must be congratulated on its simplicity, versatility and performance which is second to none. And in skilled hands can be made to look very realistic

 

From a design and engineering point of view it has worked excellently. For years it have worked extremely well and supported two different gauges. 

 

 

[martin_wynne]

1 hour ago, tynewydd said:

This degree of design freedom, as I understand it from the excellent help material at Templot, would have been uncommon in much of the prototype because the trackwork was usually assembled in parts from sets of stock items that each had fixed geometry rather than being fully "bespoke". 

 

Hi Adam,

 

The essential difference in prototype design is that the switches (moving point blades), and crossings (frogs) are treated as two completely separate items. There is a huge range of sizes of each. They are combined to create all the usual track formations -- turnouts, diamond-crossings, slips, tandem turnouts, etc.  There are certain well-established combinations of sizes to create a turnout, but the designer is free to use any combination of switch size and crossing size he chooses where necessary.

 

In addition, although the relative alignments of the rails are fixed within a given switch or crossing, they can each be laid straight, or curved onto any radius.

 

The result is that UK prototype track design is in fact very similar to the Rev Peter Denny bespoke method -- you start by laying out the curves for each line, and only then find the closest matching switch size and crossing size to fit where needed. The result often looked like this -- no straight track in sight:

 

 

At least, the above applies to traditional UK trackwork design, which is often for such cramped sites.

 

In the USA and elsewhere there is a greater tendency to adopt the model approach of having a small selection of fixed items to use, and this is increasingly the case in UK track design too, with the much simplified modern track layouts. Although of course the sizes are very much longer than the Peco designs.

 

cheers,

 

Martin.

Edited January 30, 2021 by martin_wynne
photo added

[RobinofLoxley]

Just look at the sleepers in that photo - no two the same length

[Pacific231G]

On 30/01/2021 at 09:21, hayfield said:

 

David

 

The whole idea of Peco's turnouts and crossings is not to provide a prototypical look or performance, in fact quite the contrary

 

Very cleverly they have produced an interchangeable system of turnouts and crossings of differing sizes which are very easy to use and most of all work very well. In fact it is so good at what it does its customers are very happy to turn a blind eye to it being under scale (as its an H0 system) and its looks, But Peco must be congratulated on its simplicity, versatility and performance which is second to none. And in skilled hands can be made to look very realistic

 

From a design and engineering point of view it has worked excellently. For years it have worked extremely well and supported two different gauges. 

 

 

 

I think you mean it has supported two different scales and, when he introduced Streamline, Pritchard made the decision to make it consistently to H0 scale rather than persisting with one or other of the compromises inherent in using a different scale for the track from that used for the stock running on it (or modelling narrow gauge track if you prefer to look at it that way).

 

I agree with you about it working very well but not that there is limited regard for prototypical appearance.  In H0 scale the sleepers are the correct size, the gauge is spot on and the sleeper spacing  is correct for 60cm spacing which is closer than on most British railways (but used on HS  lines) but common for fast main lines in the rest of Europe (American tie spacing is much closer and the ties are narrower) Within that the basic "three foot radius" turnout is  as prototypical for an unprototypically sharp turnout as any reliable and affordable mass produced model track probably can be. The transition curve through the closure doesn't look wrong and, apart from some of the timbering (especially the solid  plastic supporting the vee crossing) and the heavy box containing the point locking mechanism  I don't see anything inherently wrong with its geometry. It can be made to look more realistic by replacing said point locking mechanism with a simple tie bar and the  plastic check rails with metal rail and probably doing something with the timbering at the heel. Planed rail for the point blades would look better than the folded sheet but that would require additional manufacturing processes especially as the folded sheet includes the loose heel.  

Also ,given that  as Martin points out, British trackwork was traditionally laid on site and tailored to it  no system of pre built turnouts or crossings is going to look quite the same. Elsewhere it was far more common to order from the railway's internal (or manufacturer's) catalogue  say a long or short left hand tan 0.13 turnout and it would probably come ready assembled as a switch panel, an intermediate panel and a crossing panel. There would though be some  scope for curving the first two panels  though a symmetrical (Y)  turnout was a different catalogue item. 

 

 

 

I'm not sure what you mean about prototypical performance. Surely the job of pointwork*, real or model, is to enable rolling stock to move between tracks without derailing and wiithout itself falling apart. So far as that goes Peco's pointwork perfoms very well. 

 

*Whatever British PW engineers think, I refuse to say "switch and crossing work" because it's such a clumsy term within a sentence.

 

Edited January 31, 2021 by Pacific231G

[ElTesha]

Sorry if its a problem awakening this thread but does anyone have copies of the Peco streamline turnout plans that they used to publish on their website, they seem to have disappeared on the latest iteration of the site.  I would like copies so that I can test my new layout before commiting to th ereal thing, any scans or pictures would be great.

 

Best regards and fingers crossed,

 

TerryD

[martin_wynne]

32 minutes ago, ElTesha said:

Sorry if its a problem awakening this thread but does anyone have copies of the Peco streamline turnout plans that they used to publish on their website, they seem to have disappeared on the latest iteration of the site.  I would like copies so that I can test my new layout before commiting to th ereal thing, any scans or pictures would be great.

 

Best regards and fingers crossed,

 

TerryD

 

Hi Terry,

 

Still available for each item separately -- click the link on each one here:

 

Martin.

Edited March 25, 2023 by martin_wynne

[ElTesha]

Problem solved re Peco turnout plans, Hope it's not caused any sleepless nights😉

[Peter Eaton]

SleepERless nights ?

Edited March 25, 2023 by Peter Eaton
ER