Cross over on curved track

[Paul4256]

To start with, I apologise if this has been answered before but so much has been written about using curved points that at my age, I may not be around long enough to read it all! 

On my layout, I have a double main line heading out of the station, curing to the left. I want to include a cross-over at this point (mainly because that's how the real station was!) but am struggling to figure out if I can do this easily. The curve is made from 3rd & 4th radius curves.  The curved points I have seen look much more of a gentle curve that this.  Anyone know if I can do this?

The image below show the real railway back in the 60's, you can just see the cross-over on the right hand edge.

 

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[Phil Bullock]

This thread has information but may not give you the answer you want! 
 

Curved point geometry

[ITG]

Your solution may depend on what kind of track and which scale you are using? As you quote 3rd and 4th radius, that suggests flexi of some kind, but which rail profile code?

the Streamline 00 code 100 curved points are nominally 1524mm and 762mm outer/inner respectively, but you may be able to fit them in.

 If you are prepared to consider using items from their HO range, there is a lot more variety.

[RobinofLoxley]

Peco has a curved point in the streamline range that has a small change of angle - maybe 12 degrees for the inside radius? You can sometimes mistake them for ordinary turnouts. On the other hand the Setrack point (Hornby also) have 2nd and third radius curves. Quite a lot of stock can't get round the interior curve of these as per the thread that Phil linked to. 

 

Even if the Streamline point isn't sharp enough it may be possible to graduate sharper transitions going into and out of the point. Depends on the available space amongst other things.

[Michael Hodgson]

One curiosity of crossovers on curves is that you need one left hand and one right hand point, whereas on straight track you use two lefts for a trailing crossover and two rights for a facing crossover.  Worth remembering if you're going to have to buy them.

[Philou]

A picture or drawing of the geometry involved would be useful - however depending on the form of the junction intended - you can make a trailing junction by using a curved R/H point on the outer curve and a L/H 'normal' point on the inner curve (and vicky-verker for a facing junction) as mentioned above by @Michael Hodgson. That's what I'm proposing at several locations on a layout of my own.

 

Cheers,

 

Philip

[Harlequin]

If you’ve got enough space then don’t worry about the curved turnouts having a different radius to the rest of the curve. In fact, you can use it to your advantage because the curved turnouts can form a gentle transition into the main curve.

The streamline curved turnouts turn by 8 and 20 degrees at the radii mentioned above. You would need to insert some spacer track to take up the difference between the Streamline spacing and the Settrack spacing.

There are also Settrack curved turnouts with R2 and R3 radii. I can’t remember the angles of those offhand but they are known to be more troublesome than the Streamline turnouts.

What you really need to do is draw it out in track planning software.

Edited January 2, 2022 by Harlequin

[Compound2632]

1 hour ago, RobinofLoxley said:

Peco has a curved point in the streamline range that has a small change of angle - maybe 12 degrees for the inside radius? You can sometimes mistake them for ordinary turnouts. On the other hand the Setrack point (Hornby also) have 2nd and third radius curves. Quite a lot of stock can't get round the interior curve of these as per the thread that Phil linked to. 

 

Even if the Streamline point isn't sharp enough it may be possible to graduate sharper transitions going into and out of the point. Depends on the available space amongst other things.

 

The Hornby Setrack curved points are second radius (438 mm) on both routes but with a 67 mm-long straight section for the outer curve whereas the Peco ones use second and third radii.

 

The Peco Streamline curved points have a much greater radius than third (505 mm) or fourth radius (572 mm) - nominally 1524 mm on the outer and 762 mm on the inner curve but the latter may actually be rather less at its tightest.

 

So you've Hobson's choice: Setrack, which is a tighter radius than your main curve, or Streamline, which is gentler. Either may be a geometrical embarrassment but RT stock should pass happily enough through both.

Edited January 2, 2022 by Compound2632

[KingEdwardII]

5 hours ago, Paul4256 said:

The curve is made from 3rd & 4th radius curves.  The curved points I have seen look much more of a gentle curve that this.

I suspect that the curved points you have seen must be the Peco streamline ones, which have much larger radii than 3rd & 4th radius settrack.

 

I've certainly used pairs of curved Peco streamline points to make crossovers on curves - and they work very well. All my locos, including 8-coupled, pass over these crossovers very smoothly. If you're using settrack, using the streamline points may be problematic - they certainly mean having the double track curving much more slowly through the crossover than you'd get with 3rd & 4th radius curves. This may not work for you with the space you have available. It also almost certainly means using some flexi track to build that part of the double track, even if the rest of the layout is constructed using settrack.

 

Yours, Mike.

[ejstubbs]

On 02/01/2022 at 21:17, Compound2632 said:

The Hornby Setrack curved points are second radius (438 mm) on both routes but with a 67 mm-long straight section for the outer curve whereas the Peco ones use second and third radii.

 

The geometry of the Peco and Hornby Setrack curved points is identical for all practical purposes.  This diagram (originally from Antics web site IIRC) shows how both manufacturer's products can be to make a crossover between and R2 curve and an R3 curve:

 

 

Note that the combination of track sections to make a curved turnout is the same in both cases.  It may be worth bearing in mind that the outer track, although nominally R3, is made up of a combination of R2 curves and short straight sections - this would likely be an issue for any rolling stock that doesn't like R2 curves.

 

The Streamline curved points are probably a significantly better bet for reliable running, but they require a lot more room to construct a crossover on a curve - I reckon more than double the overall curve radius cf the nominal "R3" using Setrack, which for the space-constrained may not be feasible.  You'd basically be using up 18" or more of extra baseboard in each direction.  While using ordinary (i.e. 'straight') Streamline points with Setrack is reasonably straightforward, incorporating Streamline curved points in to an otherwise Setrack-based design is another level of complication IMO.

Edited April 9, 2022 by ejstubbs

[Compound2632]

One can have a great deal of fun playing with the Setrack geometry to get closer-to-prototype track centres on the straight (roughly 48 mm, the prototype being closer to 45 mm in many cases). Works for all but the biggest engines and longest carriages - up to 57' / 60' carriages clear each other. Key to this game is use of the R628 curve as a transition curve:

 

Edited January 5, 2022 by Compound2632

[Paul4256]

Thanks everyone. Plenty to ponder on.

[Sol]

I have use Tillig curved turnouts with my code 75 track without any problems & they have a better range of curved turnouts than the two from Peco,

[47406]

On my previous layout I had a number of Peco Streamline curved points in the track, I didn't quite have the room to do everything I wanted so used the curved points to try and make the best use of the space by putting a junction just before the tracks came to a long straight section. I found that I needed to do quite a bit of tweaking and adjusting the positioning to get things running reliably, but I wouldn't say I ever got them to the point where they were as reliable in operation as regular points - probably 95% or more reliable running.

 

I also had a single Settrack curved point on the entrance to a yard on that layout. That caused me a lot of problems in operation, a lot of derailments.

 

My current layout is a big U shape with double track forming a circuit around the inside & outside of the U. At the top of the U on the inside I used curved points again to give me enough space on the straight to have a pair of loops that would hold full length trains,  like a 56 + 23 MGR hoppers. What I did was a little different though - on the outer track of the curve is a Peco Streamline point which links to a Shinohara one with different geometry on the inside of the curve. It lets me make the best use of the curved section, but I did have to adjust how the tracks are spaced between the junction & the viaduct which is 90' off to the right. I have been running trains on this layout for 3-4 years now and I am reasonably happy with how this pair of points work. There are a couple of Bachmann 37s that occasionally derail on the Shinohara one, but that is very infrequent.

 

The one thing I would offer as a suggestion is to test run your stock as much as possible, for as long as possible before you "commit" to the track layout with curved points (cutting holes for point motors, putting down ballast, that sort of thing).

 

Here's what my weird Peco/Shinohara combo looks like:

 

 

Edited January 8, 2022 by 47406

[Suzie]

47406 shows how to do it in the most space saving way. You really will be best using Streamline or similar and put the crossover in the transition part of the curve where the very large radius will not cause a sudden change in radius.