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Handlaid Curved Turnout Frustration

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  • Member since
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  • From: Bloom County
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Handlaid Curved Turnout Frustration
Posted by potlatcher on Wednesday, March 24, 2010 11:34 PM

OK, I've been following the "modified Tony Koester method" for handlaying turnouts for a couple years now.  For me, this means pre-laying the ties on roadbed, with PC ties replacing wood ties at strategic points, i.e. headblocks, frog & guardrail locations, and a couple selected locations for maintaining electrical continuity.  I notch the stock rails and form and file the points, frog rails and closure rails by hand (no jigs).  The rails are soldered to the PC ties and I fill the frog with solder and cut the flangeways with a hacksaw blade.  Once it all appears to work, I drive spikes in some of the wood ties, solder in guardrails and the throwbar and cut gaps at the frog.  For the first stage of my layout, all the turnouts were straight #5's, and although none of them were perfect, I felt pretty comfortable with my method.  By the way, all my rail is code 70.

The second stage of my layout, however, required me to lay four curved turnouts and one straight one.  I had to learn as I went, modify my method slightly to compensate for the curved geometry, and tweak the finished turnouts a little for them to be (mostly) derailment free.  Then, last week, I realized that although all my four-axle diesels ran through the curved switches just fine (no six-axles on my RR yet), I'd never run my lone steamer (a Spectrum 2-8-0) through them.  Sure enough, the 2-8-0 will not successfully navigate three of the four curved turnouts.  It handles the straight one just fine, which proves there's nothing wrong with my basic technique.  And, it handles one of the curved turnouts without any noticable problems.

The main problem occurs mostly at the frog, and in most cases it seems the long wheelbase is binding up as it tries to negotiate the curve, either slowing the engine down or causing the flanges to ride up out of the frog.  Again, the curvature on the turnouts is not excessive - on one of the problem switches, both radii are definitely what I would call broad.  I have gone over each turnout with my NMRA gauge - all dimensions appear to be within standards.  And, I can see no noticeable difference between the one curved turnout that works just fine and the other three.

Clearly, I'm hoping I can just tweak the turnouts to fix the problem, but I am also resigned to tearing them out and trying again if I need to.  Are there any secrets to successful handlaid curved turnouts that someone can pass on to me?  Is there a good reference (site or book) that I can go to for guidance?  If I were to try using a CVT kit, how do I figure which number (5, 7, 9, etc . . .) to purchase to fit my custom combinations of radii?

Thanks in advance for whatever help you can offer!

Tom Hillebrant

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Posted by cx500 on Thursday, March 25, 2010 1:46 AM

 A couple of thoughts.  First, though, I am assuming the the curved turnouts have the diverging track coming from the inside of the curve, in other words both curves are of the same hand.  Is it only on the inside curve that you are experiencing this problem?

The track gauge on a tight curve should be somewhat wider than minimum so there is room for the flanges of a long straight wheelbase.  I believe even the prototype would do this in the steam era if they had big engines and sharp curvature.  Perhaps 1/2" on the real thing, but you might have to ease it a little more in HO scale terms.  Make sure the guard rail at the frog keeps the wheels from picking the point of the frog.

I assume you have checked the gauge of the steam locomotive wheelsets too.  If it is fractionally wide that would also contribute to a tendency to bind in the curve. 

Most likely a slight tweak is all that will be necessary.  Good luck.

John

 

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Posted by trainnut1250 on Thursday, March 25, 2010 3:34 AM

Tom, 

Don't tear them out, I'm sure you can tweak the turnouts into spec...I have scratchbuilt a couple of curved turnouts, so I am by no means an expert. I had very similar problems to yours on both of mine.  I ended up loosening up the tolerances in both cases to fix the problem.  I spent hours messing with the switches to get them right, but they are very reliable now.  It is very hard to offer advice without being able to see the turnout and watch a loco run through it but here goes.

A few suggestions/Questions:

1. Are you sure your radi are correct and not too tight?

2.  On the problem switches does the loco run through in any direction smoothly?

3.  Does the loco derail or just bind?

4.  Is the loco picking the point or is it binding laterally as moves through?

 Use an optivisor and watch the loco run through the turnouts until you have a good idea exactly how it is hanging up.

Suggestions (tempered by what you learn from above):

 1.  Try adjusting the guard rail gaps to be wider if the loco is not picking the point, tighter if is.

2.  Check the depth of your frog groove.

3.  Recheck your clearances from the frog point to the stock rails, possibly adjusting the rails or frog if tolerances are too tight.

4.  look for solder blobs on surfaces where they might interfere with the tracking of the loco.

 I hope these help. Maybe Sperandeo, Tomikawa or others will jump in with better advice.

Fastracks offers some videos on handlaying that you might find useful if you haven't seen them. 

I left one turnout semi-operational for over a year before I solved it. I got it to work marginally while I puzzled on it and then one day I had the aha and I just fixed it.  The turnout has worked great ever since....

BTW:  the only reason I scratchbuilt the two that I did was because I could not find an RTR turnout to fit the geometry that I needed.  This is true of all of the handfull of scratchbuilt work projects I have undertaken...

Good luck,

Guy

see stuff at: the Willoughby Line Site

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Posted by locoi1sa on Thursday, March 25, 2010 5:31 AM

  Tom

 Even curved turnouts are nothing more than a series of straight sections with curved rail between them. It is more than likely the constant curve is forcing the flanges to hit hard in one area forcing it up over the rail head. Proto 87 has some good photos of curved turnouts that you can clearly see the straight sections of rail. When I get home I will post some links for you.

         Pete

 I pray every day I break even, Cause I can really use the money!

 I started with nothing and still have most of it left!

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Posted by cuyama on Thursday, March 25, 2010 9:33 AM

Because of the straight (or straighter, at least) track through the points and frog section, the effective radius into and out of that section may be a bit tighter than you intended. The longer fixed wheelbase of the drivers on your 2-8-0 seem to be binding there (from your description), which is what one would expect from this situation.

If this is contributing to the problem, you might be able to visualize it by curving a metal rule along each curved rail and then sighting straight down to see how (and how much) the rails diverge in the frog area from the smooth curve elsewhere in the turnout. You may find that you have a short section of tighter curves just before and/or after the straighter section through the frog.

Byron

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Posted by selector on Thursday, March 25, 2010 11:45 AM

Tom, you don't offer the true radii involved, but this 2-8-0 is a relatively small steamer.  It should handle radii well under 19", maybe even 17", although we'd have to test to be sure.  I doubt that your curved handlaid turnouts have a radius in them under 18"?  So, unless your engine is really the problem, I would have to conclude that you have a tolerance issue somewhere near the frog.

You say it all gauges out.  The points rails aren't splaying and allowing the engine to fall through due to flange pressure?  The guards are sufficiently wide to allow flange passage, but not so grossly wide that they allow one or more flanges to stub themselves on the frog point, or even the opposite guard?  (It can happen, believe me...)

Did you build these in situ...or on a nice flat bench surface?  Do you know for a fact that these surnouts are on a plane, both down their major axis and transversely across all rail tops?   I couldn't begin to tell you how many turnouts have given me problems because, once they were set in place and I began to run them, it turned out that they let longer steamers derail due to dips along their lengths, or a high frog point, or uneven rail heights that forced the frame ahead to tilt due to a driver axle having to lift on one wheel, even by half a mm.

Now I'll let you in on a little secret.  I built a Fast Tracks #6 double slip that was...ummm...marginal.  I was determined to salvage its greater whole of a thousand little bits that had to be shaped and soldered just so.  I had trouble with tracking.  When looking down the various paths near rail top level, I could see it was a wobbly path.  Not at all good for longer steamers.  So, I used a cut-off disk on a Dremel-type tool, and I dipped and ran sideways with the disk to straighten the path.  I just kissed the rails' flange faces where I could see the path tightening or a bit wobbly.  The rolling stock doesn't mind thinner rail heads, but flange paths are another thing...they have to make room.  It took a surgeon's determination and skill, but I did clean up the side 'walls' of the paths so that the flanges didn't keep running into tight spots.  The turnout is the one you see in images of my yard, and it works quite well.

You may have to thin the rail heads in a spot or two...maybe that is all you will need.  But those guards....they may be the real culprits.  And I am assuming you did alter the frog configurations?  I made one #10-ish curved turnout in place, and I did curve the frog a little bit.  The turnout works extremely reliably, including at track speed and with passenger cars and such.

-Crandell

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Posted by locoi1sa on Thursday, March 25, 2010 3:55 PM

 I pray every day I break even, Cause I can really use the money!

 I started with nothing and still have most of it left!

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    November 2002
  • From: Colorado
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Posted by fwright on Friday, March 26, 2010 4:29 AM

potlatcher

.....For the first stage of my layout, all the turnouts were straight #5's, and although none of them were perfect, I felt pretty comfortable with my method.....

The second stage of my layout, however, required me to lay four curved turnouts and one straight one.  I had to learn as I went, modify my method slightly to compensate for the curved geometry, and tweak the finished turnouts a little for them to be (mostly) derailment free.....Again, the curvature on the turnouts is not excessive - on one of the problem switches, both radii are definitely what I would call broad.  I have gone over each turnout with my NMRA gauge - all dimensions appear to be within standards.  And, I can see no noticeable difference between the one curved turnout that works just fine and the other three.

.....Are there any secrets to successful handlaid curved turnouts that someone can pass on to me?  Is there a good reference (site or book) that I can go to for guidance?  If I were to try using a CVT kit, how do I figure which number (5, 7, 9, etc . . .) to purchase to fit my custom combinations of radii?

Thanks in advance for whatever help you can offer!

Tom Hillebrant

Tom

My suspicion is that you have a couple of things going on - 1) a much tighter radius than you suspect on the inner path of the curved turnouts, 2) a less than perfectly aligned wheel path, and/or 3) possible incorrect misgauging or misalignment of the drive wheels on the locomotive in either the vertical or horizontal plane.

Did you use #5 frogs on your curved turnouts?  If so, the radius of the curved parts on the inner curved path is going to be very tight - probably on the order of 15" radius.  On a curved turnout, the frog # controls the difference of the radii between the 2 legs, with a small frog # having a much greater difference in the radii than a larger frog #.  Notice that the smallest frog # Walters uses for their curved turnouts is a #6.5 - and the inner path on that has been measured at 18" radius or less.  On a #5 turnout, you are starting at 26" radius curves with the other path straight.

IMHO, a better way to lay out a curved turnout is to use 2 cardboard templates, each cut to the desired path radius in the center, and each edge cut to the radius +/- 1/2 the track gauge - sort of like cardboard radius gauges.  Draw the lines on your roadbed using these - you will get a much longer turnout than you expected.  It takes quite a bit of space for 2 curves that differ in radius by 4" to diverge sufficiently.  Which is why commercial curved turnouts are usually #7s or #8s.

But I just use the radius templates and let the points and frog be curved to keep the radius constant.  I believe a constant radius is easier for a steam locomotive to track than a series of curves and straights.  Regardless of whether you use curved or straight frogs, having the correct check gauge at the inner path guard rail of a curved turnout is critical because of the side pressure looking for a flaw.  That guard rail may have to be a little longer than on a straight turnout and must accurately reflect any curves in the closure rail and frog that it is guarding.  Distance between the guard rail and stock rail is almost immaterial (as long as flanges will pass through the gap); what matters is the correct check gauge at all points.

As Selector pointed out, it is very easy to get less than perfect horizontal, angular, and vertical alignment between the closure rails and frog.  Check these very carefully.

Also, remove the pilot truck and check the locomotive on a flat glass surface.  Does the model rock longitudinally because one axle is slightly lower than another?  Do all the drivers track in a line perfectly?  Are all drivers in gauge?  Again, the greater side pressure going through the inner path of a curved turnout makes wheel back-to-back and accurate location of the guard rail much more critical.

Again, on a curved turnout of a given frog #, the inner path is going to have a much sharper radius than the same frog # in a straight #.  Going up 1-2 frog #s for a curved turnouts keeps the radii on the inner path within reason.  On a curved turnout, the frog # controls the difference in radii.  The outer path radius, in conjunction with the frog #, gives the inner path radius. 

hope this helps

Fred W

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Posted by dehusman on Friday, March 26, 2010 8:16 AM

I would suggest putting a large piece of paper over the turnouts and rub a pencil over the rails to trace the turnout.  Then lay rails or flex track directly over the rails along the inside route.  That will show you the exact path your are trying to negoiate.  You can check to see if there are any kinks or tight radii.  If that is OK, then its a matter of too tight clearances through the frogs or guardrails.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by potlatcher on Friday, March 26, 2010 10:12 AM

Thanks to everyone who has replied so far.  Of course, now that I have lots of input and some good avenues to pursue in fixing my problem, I now run out of time to work on it!  That figures.  So, next week some time, I'll try to take another look at my situation, and see which of your suggestions I can apply to get my turnouts working properly.

Thanks again,

Tom

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  • From: west coast
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Posted by rrebell on Friday, March 26, 2010 11:26 AM

Sounds like a frog problem, when hand laying frogs the sharpest point of the frog can get bent ever so slightly so it is not the same curvature and not work well, but sometimes you tend not to see it unless you look at it from in front of that point and even then sometimes it is hard to see. I have had to file this on commercial one's sometimes too.

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