[?] I want to lay a runaround track on a curve but I am having problems with the design. I am modeling in H0 scale and my turnouts are atlas #6. The curve radius in the main, outside radius, is 36" but I don´t know how to figure the inside radius and to joint the 2 turnouts.
How do you lay your runarounds on a curve?
Hi Soller,
Could be wrong, have not used Atlas, I don’t think they do curved points. I’m guessing your’re on code 100, you dont say how much the cuve is 45º, 90º or 180º no sweat, your inside track needs enough clearence for stock to pass depending on the area you run (like 89ft modern stuff,ok).
As I said if you can get hold of a pair of Shinahara or Peco curved points, L&R hand,(for a 180º say) it makes the job aload easier to line the main up into the curve, once you’ve got that pinned in place and marked you can lay the loop loosley pinned to make ajustments by rolling stock round stuff held inside, then add a couple of MM for luck. Don’t do fancy formulars.
Be in touch.
pick
I agree, using curved turnouts is the way to go in your case.
Crandell
I forget what the effective radius of the #6 curve is - it can be found in John Armstrongs “Track Planning for Realistic Operation”. What I would do is use the Walthers or Shinohara (Code 83 or code 70 or 100 respectively) curved turn outs to do this. The #8 curved turnout has an outside radus of 36 inches and an inside radius of 32-inches. If you use a left hand and a right hand you can build the curve inner and outer sections inbetween them.
Otherwise you could use the much cheaper #6 standard turn out and the curve radii of the turnout becomes part of the curve and diverges to offer the second curve which is 36 inches. To make this work the best, you’d need a left and right hand and trim as much of the straight section off as possible to minimize having a straight track in the diverging curve of the outer cure track.
Hi!
Been there, done that, but had to compromise…
As indicated, the BEST way to do the curved runaround is with curved turnouts - which Atlas does not make. Assuming you want to stay with Atlas trackage, the next best way to accomplish this is to put in a turnout on each end of the curve, so that the straight track is on the outside track, the divergent (curved) portion of the turnout is on the inside track.
Lay in the turnouts, and then draw a line x inches (3 - 4 is pretty good) from the centerline of the outside curve. This will be the centerline of the inside curve. Then, lay in flextrack from the turnout and transition it (gracefully) to the inside centerline. Obviously you want to avoid sharp reverse curves in that process.
Good luck!
Armstrong indicates a 43" radius of closure rail and 56" substitution radius for a #6. One caution: The Wathers/Shinohara curved #8 radii are 36/30, not 36/32. They overstate their diverging radii by 2" for all their curved turnouts.
Dante
If I’m not mistaken, an Atlas #6 turnout is 9.5 degrees, If your outer radius is 36" at 180 degrees, then the inner radius is 35.5" turnout to turnout.
I am in agreement with what is being suggested to you. Use a curved turnout, preferably a Walthers Shinohara #8 with a 36" radius on the outside curve and a 32" radius on the inside curve. I use these curved turnouts on my layout although not for the purpose that you intend. Just be careful to fully support the curved turnout with solid roadbed beneath it to prevent derailments.
Incidentally, I acknowledge Dante’s point about the radius of the inside curve. Walthers Shinohara states that the radius of the inside curve is 32", but Dante has indicated that it is actually 30". Using Ribbonrail metal curved track alignment gauges, it seems to me that the radius of the outside curve is actually 35" and the radius of the inside curve is 31" or maybe even 32". We run the risk of splitting hairs over any perceived or actual differences, but the main point is that the Walthers Shinohara #8 curved turnout would seem to best meet your needs.
Rich
If the curve radii are as you say, then the result is non-functional as there is only 1/2 inch distance between the track centerlines. The two tracks would overlap.
Not so, because the curves are not concentric. Since the turnouts lead into the inner curve, the center point of the inner track’s curvature is displaced inward by several inches.
I’ve used Peco and Shinohara curved turnouts and they’re great. But depending on where the divergent point needs to be, an Atlas number 8 may be better than a number 6. Note that a large radius Peco(regular turnout) is similar to a number 8, but takes less tangent length.
A quick note about laying curved turnouts. They are very sensitive to elevation change both longitudinally and side to side(super elevation). I have found mounting them and short sections of joining track on 3/16" basa wood or similar helps avoid many hours of derail diagnosis. This keeps everything in the same plane. Tjhe basa wood is easily formed into a ballast bed to blend in with your cork, etc.
Richard
Richard,
That is excellent advise, be it a piece of balsa wood or a piece of styrene or whatever. Just make sure that the base is thin enough and placed in such a way that it doesn’t raise the curved turnout higher than the connecting tracks so as not to create humps.
Rich
It’s not clear what is the Original Poster’s need. Is it to “cut in” the runaround all within the 36" radius curve? If so, then, yes, a curved turnout is necessary. With an inner radius of about 30", the PECO C83 #7 curved turnout is much more compact than the equivalent Walthers components and worth consideration.
If the straight turnouts can be located outside of the curve itself, then I think it’s more realistic for the two tracks around the curve to be mostly concentric. Something like this:
The “cost” of this better (to me) appearance versus the runaround posted earlier is a smaller inner radius. But the concentric circles approach does give a slightly longer length in the clear.
Of course, all may be moot, since we don’t know the Original Poster’s situation.
Byron
This is my idea!
The geometry whizzes may need to reply specifically, but to my eye and based upon the placement of the turnouts, you could conceivably have an inside curve that has a broader radius than the outside curve. Adding a triangle to the corner of the benchwork could definitely accomplish this.
You will need to determine and explain more about what you are trying to accomplish, as Cuyama suggested. Such as:
Are you trying to have a long enough runaround to accomodate a certain length train and need the turnouts fixed where they are?
Do you need a minimum radius for rolling equipment to negotiate?
Do you want closely spaced or widely spaced tracks for appearence?
There could be other questions as well that you may need to ponder and explain before your answer can be calculated.
Then what I sketched will work fine for you. Offset a smaller concentric curve inside the existing curve by your desired track-to-track spacing, then you may extend the tangent ends (straight tracks) and tie it into the turnouts.
hi
still an issue open:
If the distance between the curve and the turnout is to small, a double S-curve is the result.
Try to avoid that situation
Paul
Really, two curved #7-8’s will do it all for you much more cleanly. But…you gotta do what you gotta do.
Crandell
Grandell,
look at the drawing the OP provided.
My remarks were based on his drawing.
Paul
The big boys don’t run thru a switch and jerk into the curve. Better think about easement into and out of curved track. Of course all this uses up more layout room but the trains flow into and out of the curves better. Also, remember any overhanging equipment needs clearance between the tracks.