Saturday, February 11, 2017

Back to Building Turnouts

Now that I'm getting close to laying track at Pine Valley I knew I should start building the odd ball turnouts I'll need.  Lately I've actually been looking forward to building a few turnouts, I've discovered it to be a very relaxing and meditative process.

Instead of "warming up" first by building a turnout in my Fast Tracks #6 assembly fixture, I just dove right in on the "freehand" paper template since it was a pretty straight forward #8 turnout.


Although I spent about a total of two hours, construction went smoothly and the the turnout performs flawlessly.  As a side note, I finally replaced the container of flux as the lid was getting impossible to remove due to flux on the cap threads. This jar of Radio Shack flux dates back to my High School days so I'd say it had a good life. I found a nice sized replacement at a local craft store and transferred the still good contents, maybe it will last me another 25 years.

Unfortunately the next night I started on a curved #6 and that didn't go so well. When rolling a truck through the diverging route, the lead wheel will pick the frog point and try to reroute. I've tried filing various frog rails and even unsoldering the whole frog point and moving it in a bit with no change. There were also some gauge issues which I believe is from using curved rail that was made for a different turnout that I never started. I'm torn between trying again to fix it or trash it as a source for guard rails and move on.

The offending #6 50/30 radius.
Ether way I decide, live and learn.


  1. I've never built a turnout from scratch myself (kudos to you for poioneering down this road), so I can only judge from my armchair...

    Curved turnouts are very picky (pun intended...) at the frog when it comes to tolerances because the diverging radius is much tighter than it is on a straight turnout. Your #6 50/30 curved turnout uses 30" diverging radius where a straight #6 turnout uses 46" radius on the diverging route. The #8 straight uses 67" radius on the diverge. Even the broadest Fast Tracks curved turnout is still very tight on the diverging route, the #10 60/46 curved has the same diverging radius as a straight #6 turnout. A straight #10 turnout uses 117" radius on the diverging route!!!

    There are 2 places where your tolerances need to be spot on and even more so on a curved turnout and that is where the wing rails bend & meet at the frog, and also between the guardrails and the stock rails. The wing rail bends themselves need to be a very sharp bend at the frog and have no curving in them at the bend, or else there will be enough room for the wheel face to fall inside the gap and pick the frog.

    Maybe in your case the guardrail gapping is too wide and allowed the wheels to slide too far at the frog thus causing them to pick the frog. Standard HO guardrail gap is .048" but Proto-87 guys go down to .021-.023 because they usually use code 68 (a .068" width wheel and actual prototype scale wheel) to code 80 wheelsets (semi-scale) which require much tighter guardrail gapping tolerances. I believe most wheelsets from the better quality manufacturers (Kadee, Walthers, Accu-Rail, etc.) are RP-25 (code 110 or .110" wide) wheels, which are less forgiving than pizza cutter wheelsets from lets say older Bachmann, Con-Cor, etc., but they should negotiate ok if your tolerances are within NMRA guidance.

    Point being (pun intended once more...), maybe the curved turnout can be salvaged if you just check & tighten up the guardrail gapping between the guardrail and the stock rails? If you don't have one, I have an inside caliper from my machinist days that you can use to check the actual gap instead of using an NMRA gauge.

  2. As a follow on to my first comment...

    I just checked and a dime is .050", which is .002 thicker than the .048 gap recommended by NMRA. I was able to stick the dime in the gap between the guardrail and stock rail on an Atlas turnout and it actually rattled around a little, which means the Atlas turnout has a larger gap than NMRA specifies.

    If you could find a small piece of sheet brass or steel somewhere (soup can lid?) in the .040-.045 thickness range, you could stick that in the gap as a jig for soldering the guardrail and it would give you a good gap tolerance that might solve your problem.

    1. That was an excellent write up of potential issues, thanks Jeff! As for that bad turnout, like you confirmed, I now feel the problems lie in the frog wing rails and possibly guardrails. I built a #6 with a sharper radius of 36/24 last night and took more care to put a good sharp bend in the wing rail this time. Even with out guardrails it performs much better. I also made sure to curve each rail in my bender for each specific rail. I do have a caliper but I mainly use my NMRA track gauge for clearance checks.

  3. Awesome! Heck if you can get it to perform better even without guardrails I would say you have success. When you are successful with projects like this then I know I have a local expert I can shoot up a flare for someday when I get building.