Crossovers using curved points

[CaptainBiggles]

Afternoon all, first post.

 

Am trying to sketch up the throat of my station & trying to make my platforms longer by starting the crossover on a curve rather than a straight. I want to use Peco's 00 curved points but what radius does that make my 2 curves? I know the inner curved-point rad is 30" & the outside is 60", so how do I use these to switch between 2 curves the inner is 30" & the outer is c. 33" rad?

 

Please help??

 

Joel

[Titan]

Wecome!

 

Unfortunately you cannot use them and have a smooth curve on both tracks due to the differing radii. If you wish to keep the tracks parallel, you will have a 33 inch radius in the outer track when it is alongside the points in the inner circuit, and the inner circuit will have a radius of 57 inches alongside the outer points. ie the radius will change as you travel through the crossover. This very approximately is equivalent to an average radius overall throughout the crossover of 44 inches for the inner and 47 inches for the outer. This is where a track planner on the PC really comes in to its own!

[66C]

Hi Joel

 

Try to think in terms of varying the radius of the curve as it approaches your platforms rather than looking at the curve as being restricted to purely circular arcs.

 

The actual combination of curved points will depend on the relative positions of the platform and the theoretical radius of the approach curve - I assume that you are attempting to have straight track through your platform. The combination of radii from the curved turnouts could be used to give an approximation of a transition curve - real railways do not plan track alignment using circular arcs like set track!

 

Another approach would be to use a curved turnout on the outer curve and combine this with a straight turnout diverging from the inner curve.

 

If you can, post a sketch of what you have in mind and then others may be able to offer more advice.

 

Bear in mind that you can download templates of the Peco turnouts from their website so you can play about with your design before committing cash to purchases.

 

Regards.

[brossard]

For our club layout we wanted a large radius curve (~ 13 ft) across the main scenic section and station. We realized at that point that Peco points wouldn't do. We decided to bite the bullet and make our own. It worked out very well.

 

John

[Colin_McLeod]

I have successfully used Peco curved points for crossovers, including on a location with two crossovers one after the other. I found it nearly impossible on paper, but in practice it was very easy. Make sure there is plenty of space (using the templates) then just buy the points, connect them together and then fit your remaining track around it. It works, looks very well and the change in radius is not noticeable.

[Flying Pig]

A variety of arrangements on XtrkCad with approximate radii. Large or medium straight points look best on paper to my eye, but the effect at full size may well be different.

 

[chris p bacon]

Using code 75 I did the same as Colin.

 

As I am modelling a location I had no choice but make the crossovers using curved points, I have 2 and they work well.

 

I worked up a rough track plan on paper for the layout, then used paper templates on the boards, this worked fine for 90% of tracklaying but you can't beat roughly laying some track and seeing how it fits together, this was the only way I could use them as on paper it wouldn't work.

In practise they take a pacific and 9 coaches at speed without problems, Just what the doctor ordered.

[70021 Morning Star]

Hello guys,

I'm slightly confused about the difference between a 'turnout' and a 'set of points'. I'd always thought they were the same thing, but then I came across Pico's "SL-184 Catch Turnout Right Hand Electrofrog code 75 rail OO Gauge". This 'turnout' appears blocked by the rail on one side, as well as not having the expected three pairs of facing/trailing track connectors. Can anyone explain what it's for, please?

Thanks,

Rick

[lilchris]

SL 184 is a catch point Rick, used to protect the main line from goods traffic running astray, I think.

[Pacific231G]

Hello guys,

I'm slightly confused about the difference between a 'turnout' and a 'set of points'. I'd always thought they were the same thing, but then I came across Pico's "SL-184 Catch Turnout Right Hand Electrofrog code 75 rail OO Gauge". This 'turnout' appears blocked by the rail on one side, as well as not having the expected three pairs of facing/trailing track connectors. Can anyone explain what it's for, please?

Thanks,

Rick

A "turnout" and a "set of points" ARE the same thing Rick. Turnouts are what Americans, PW engineers and pedantic railway modellers (who don't believe in synonyms) call them and points or sets of points are what everyone else in Britain, including generations of railwaymen (and the Oxford English Dictionary) have called them since Stephenson's time. 

 

The use of the word "points" or "turnout" may have been the source of much pointless discussion but Peco seems to have become so oversensitive to the idea that turnout is the only "correct" word that they've taken it to the point of absurdity by adopting terms completely unknown to the full size railway world* like turnout motors instead of point motors or point machines (British English)  or switch machines (US English) It seems they've now gone further and invented "catch turnouts" when they mean "catch points" .

 

In railway (or even railroad) usage there's no such thing as a catch turnout. in Britain they're called catch points or trap points. Trap points are generally those placed on sidings to stop or trap runaway vehicles from fouling a running line. They were also once known, at least by the GWR, as safety points. Runaway catch points or simply catch points are basically the same device but installed on a running line to catch runaway wagons (especially before they were fited with continuous brakes) running the wrong way down a gradient before they could do more serious damage. Some railways used the term catch points to cover both uses.

 

In US (railroad) English, what we call trap points are normally referred to as split-rail derails or simply derails though that term also includes various other devices, known as derailers in Britain, mounted over the rail to achieve the same result and swung down to let wagons pass.

 

Some trap/catch points are the single bladed type offered by Peco but they could also be two bladed without a crossing or even a complete turnout with a switch and crossing leading nowhere except onto the ballast or to a stub siding or sand drag.  In America and Europe derailers seem to be far more common than catch points but it's the other way round in Britain.

 

* I have seen the term "turnout control" in MRJ and I wonder why because I've yet to see a turnout lever in a signalbox.

[Gwiwer]

When I planned my layout it included several of the curved-both-tracks points in the Peco Streamline range.  I realised that with only straight-track diamonds available in the same range there could never be equal track spacing and entirely smooth curves.

 

I used transition radii throughout and the overall effect is perfectly acceptable though the appearance can differ depending on where you stand to view.  Some angles show a distinct curve-straight-curve sequence across the diamond while from other points of view it appears smooth.

 

I have received several comments over the years that observers hadn't realised I had curved points in use at all for some time.

 

You can build your own diamond with one or both routes curved or you can compromise as I did and accept what is available over the counter.  It's also worth noting that when you fit two curved points to a diamond the two toe-ends of the points will not be exactly parallel.  Don't build your track up with parallel ends then try to build the junction as it won't work.

 

The curve radii Peco use are such that high speed running is possible in both directions without mishap though there can be a tendency for trains crossing the diamond to jerk from curved to straight to curved because of the fixed geometry.

 

"Set of points", "Switch" and "Turnout" are all one and the same.  Peco also offer "catch points" in both right-hand and left-hand variants.  These derail in those respective directions when used as either catch (derails runaways in the wrong direction) or trap (derails runaways / overshoots in the right direction) points - make sure you get the right one!  

 

A view of the junction showing the sweeping curves and brief straight lengths necessary with this arrangement.

 

 

This one shows how I compensate for the different spacing of the tracks; the "six foot" between the tracks widens slightly through the curve (as indeed it should) and is grassed in.  

 

 

Here's a short clip showing a train taking my double-curved junction and in which it it possible to see the brief straightening up as the train negotiates the diamond before re-entering the curve.

 

[edcayton]

Lovely looking layout Rick. The backscene is particularly realistic but perhaps a tad over-scale

 

Ed

[Clive Mortimore]

A "turnout" and a "set of points" ARE the same thing Rick. Turnouts are what Americans, PW engineers and pedantic railway modellers (who don't believe in synonyms) call them and points or sets of points are what everyone else in Britain, including generations of railwaymen, have called them since Stephenson's time. 

 

Edited

 

* I have seen the term "turnout control" in MRJ and I wonder why because I've yet to see a turnout lever in a signalbox.

That is a wonderful description......well done David.     

[70021 Morning Star]

Ah, now that's a great and very comprehensive answer, David (Pacific231G) !
 
So, 'trap points' are not particularly useful in the functioning of a model railway, but might be needed when depicting a specific historic location that had them. The Pico SL-184's 'slider control' now makes sense.
 
..."derailers" huh; yes, they're very popular on my locomotive-performance and close-coupling test track -- probably, for all the wrong reasons !
 
Many thanks,
Rick

[Pacific231G]

Ah, now that's a great and very comprehensive answer, David (Pacific231G) !

 

So, 'trap points' are not particularly useful in the functioning of a model railway, but might be needed when depicting a specific historic location that had them. The Pico SL-184's 'slider control' now makes sense.

 

..."derailers" huh; yes, they're very popular on my locomotive-performance and close-coupling test track -- probably, for all the wrong reasons !

 

Many thanks,

Rick

I'm glad you found it useful. You could get away without any catch points as they could always be "somewhere else" and I'm not sure how often they are used nowadays anyway.

Trap points don't add to the operation but, rather like proper signals, they add a lot to the authenticity of a layout as they were and still are used to protect running lines from runaways in yards unless the layout of the yard does that already by having a headshunt.

 

I wasn't absolutely sure of this but I've just used Google Earth to look at a few yards around Ealing and they all seem to have them and they all seem to be the double bladed no frog type. If you look at the junction at West Ealing you'll see a set protecting the West of England main line from anything escaping from the PW yards there. A vehicle coming off on these trap points would actually be diverted straight into the path of a down train using the Greenford Branch but there's a low speed limit there and that would be far better than something getting in the wayof a 90MPH DMU on the main.

 

When designing them into a track layout you need to think where they would divert a rogue vehicle to and how that could be made as harmless as possible. The type i've just described could be made very easily just by cutting a turnout at the toe end of the switch blades and you'd just need to operate it in tandem with the points accessing the main just as you would with a crossover but it wouldn't need any wiring.

 

This reminds me that I've not yet fitted dummy derailers to the sidings on my French layout.

[70021 Morning Star]

Thanks, again, David.

Totally agree, any French layout needs derailers. Lots of them! ;-)

Cheers,

Rick  

[Pacific231G]

Thanks, again, David.

Totally agree, any French layout needs derailers. Lots of them! ;-)

Cheers,

Rick  

Judging by recent news of RFF's plan to close most of the remaining goods only lines, I think that they and SNCF are quite capable of derailing the whole thing themselves. Apparently the French government have got so fed up with them that they're looking to transfer investment into roads.

[70021 Morning Star]

Track Design Software

 

Hattons have just told me about a Track/Layout Design programme on www.anyrail.com.

 

It's a free download and has a user manual.

 

Rick

[sub39h]

If you use Roco curved points you can get a track geometry similar to what you've suggested. Apparently they are a close match to Peco, but slightly more Germanic in appearance. (See http://germanrail.fr.yuku.com/topic/5590/HO-TwoRail-Track-for-Germany#.VKz2SSusWSo.) They are eye wateringly expensive though compared to Peco points! 

 

If you remove the points and lay a piece of flex track between the two end points the inner radius works out as having (in a clockwise direction from the 12 o'clock position) a short 27mm straight section followed by a continuous 831mm curve, the outer a 27mm straight followed by a continuous 882mm curve. (These are roughly 32 and 3/4" and 34 and 3/4" each, all with a 2 inch spacing). 

[Londontram]

Lovely looking layout Rick. The backscene is particularly realistic but perhaps a tad over-scale

 

Ed

No that's not over scale Ed, it's the Eden project!

[Gwiwer]

If only I had the biomes that Eden does.  I wouldn't have to spend days at a time netting to keep birds off and possums out.  In order to achieve the latter the ground-level security has to be so tight (tent pegs every foot) that harvesting also becomes a time consuming chore.

 

Those little people on the model farm next to the curved points have it easy!

[SRman]

Sort of like this?

This crossover uses the Peco large curved points, with my addition of third and fourth rail for London Underground stock.

There is a short extra piece of track between the two points to stretch the track spacing slightly.





The point at the upper right is also a curved point, and while it is actually leading to a branch line / short siding, it also almost forms another crossover within the context of the photo.

[garethashenden]

A "turnout" and a "set of points" ARE the same thing Rick. Turnouts are what Americans, PW engineers and pedantic railway modellers (who don't believe in synonyms) call them and points or sets of points are what everyone else in Britain, including generations of railwaymen (and the Oxford English Dictionary) have called them since Stephenson's time. 

American railroaders call them switches. American modellers call them turnouts to differentiate from electrical switches.

[roythebus]

Catch points are always spring loaded and always in the trailing direction, designed to derail runaway vehicles; trap points can be found in the facing or trailing direction and are always operated by the signalbox or ground frame and designed to prevent a conflicting movement.

 

With the withdrawal of unfitted goods trains in the UK there is now little need for catch points. Trap points "could" have prevented the Ladbroke Grove crash by preventing the errant DMU heading towards the oncoming HST, bit I digress.

[Judge Dread]

 

 

 Trap points "could" have prevented the Ladbroke Grove crash by preventing the errant DMU heading towards the oncoming HST

Space is the problem when a central track splits both ways into two running roads. I have memories of a similar set-up in York where problem of running out of the central loop was solved by both point blades moving independently.

It should be mentioned that when trap points are fitted, and there is a track circuit, there is installed what we called a "policeman". It's a small block fitted to the inside of one of the trap rails which is electrically connected. It would be broken free by any derailing vehicle, thus making the track circuit show "occupied" and give away the offender's presence, even if it ends up clear of running rails but still an obstruction.This action would prevent the locking being freed for that pair of points. 

To explain further, in essence a battery at one end of a track circuit sends a current through the isolated running rails. This current is detected at the far end of that circuit and powers a relay which "picks up" and in that state does nothing. The presence of any vehicle on that track circuit, short circuits the current and the unpowered relay "drops away" allowing a separate power source to illuminate a light on the main panel or any other control. The loss of the "policeman" open circuits the track circuit and gives the same effect as a vehicle standing on it. This description must be taken as a vast  simplification of the whole concept of track circuiting in general.