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I've built several #10 turnouts with Fast Tracks jigs and they don't allow wheel drop with FVM narrow tread wheels. It's totally possible. Striking the balance on the flangeways is not the most straightforward thing, to be sure. With the Fast Tracks method, you solder the two inner rails on the trailing frog side together first at the angle, then put them in the jig and solder to the ties. If you push them too far into the frog, your flangeways are narrow. If you pull them outward, they are too wide for narrow FVM and BLMA wheels (though fine for just about anything else. The tolerances on the jig do allow for about that much slop, and the differencethe jig allows gets worse the bigger the turnout number . If you want to use narrow tread wheels you want to strike a balance kinda right in the middle. That is, unless you want to be checking your loco wheels' guage with callipers every time you maintenance them. In my experience If you really build turnouts tightly to NMRA most loco wheels from the factory will have issues, as well as many older non-MT wheelsets. Correcting guage on loco wheels is doable, but needs to be more precise the finer you want to make your flangeways. Now, a curved turnout is going to be trickier, as well.
Before I get deep into this, the problem you're having with your one curved turnout isn't due to any of your wheelsets' tire width, flange depth, or flange width. The problem is with your turnout, and it has to do with the turnout's "Track Check Gauge."A photo of the offending turnout taken from directly downward with the frog centered would be a great help. Since I don't have that, I'll tell you how to minimize the problem.I hand-build all of my N-scale turnouts (not using any Fast Tracks jigs, fixtures or tools) and I've been doing this from the late 1970's using Gordy Odegard's article in the February 1976 issue of Model Railroader as a starting point.Since those early days, I've experimented with and explored various methods to aid me in getting turnouts that look good, work as flawlessly as possible, are robust and don't take me too long to build.I've learned that there are a few places on N-scale turnouts that need special attention to work reliably. One of those places is at the frog where you are having problems with your narrow-tired FVM lo-pro wheelsets falling into the frog of one of your Fast Tracks-style hand-made turnouts.There could be several things contributing to this problem, so let's go through what to check on your turnout.First, you'll need your NMRA N Standards Gage.Look at your curved turnout and see if the point of the frog is long and sharp. It needs to be as long and sharp as possible for functioning the best, and to minimize wheel drop.Look at the frog wing rails and see if they're parallel to the frog's point rails.Using the NMRA "Gage"...which I will now call a "Gauge"(capitalized)...carefully check the gauge of all of your trackage in the frog area...and note if there is a spot or two where the gauge is wider than it should be. Make sure to check the gauge between the closure rails and their respective stock rails. The track gauge between the frog rails and the respective stock rails should be exact...the rails forming an "interference fit" so that the NMRA Gauge track gauge prongs are touching both railheads where you're checking the track gauge, but will still slide through. The frog area should be put together so that the track gauge between the frog rails and the adjacent stock rails is an interference fit (both rails touching the "TRACK" gauge prongs on the bottom of the NMRA Gauge, but the Gauge being able to slide down the track.)The frog's wing rails should be an interference fit between the wing rails and the frog rails on both sides of the frog...once again the FLANGEWAYS prongs sliding through the gap, but touching both rails.Sliding the NMRA Gauge towards the throwbar, the gap at the sharp bend where the frog's wing rails turn into the closure rails, should be wide enough to let the NMRA Gauge pass through, but tight enough to NOT ALLOW the FMAX prong to pass through. "FMAX" means "Flangeway Maximum" but, it should not pass through any of the flangeways at the frog nor between the stock rails and guardrails (check rails).Using the NMRA Gauge's FLANGEWAYS prongs, confirm that the track check gauge between the flange side of the guardrails (check rails) and the frog rails is an interference fit. This is probably the most important part of your turnout to get the spec's correct...so take time to confirm that this measurement allows your NMRA Gauge's FLANGEWAYS prongs to slide through, but still touch both the frog rails and the flange side of the guardrails simultaneously. If your NMRA Gauge is a little tight here, that's okay (just a LITTLE tight), but if it's too wide, that's bad.Since your turnout is soldered to PCB ties, you should be able to move your rails from side to side to get your gauge and clearances correct by heating up your rails and sliding the rails with tweezers, then holding in place after you remove your iron until the solder freezes. I doubt any additional solder will be necessary, but a little flux would ensure a good solder joint. To minimize wheel drop, the flangeways between the frog wing rails and the frog rails should be a tight, interference fit. If the point of your frog isn't as long and sharp as it could be, that will contribute to wheel drop.You'll note that I said "To minimize wheel drop..." because you're not going to eliminate it, nor do you need to totally eliminate it.Because N-scale flanges vary quite a bit in their height measurements, it's not really practical to fill the frog with solder or brass strips for the flanges to ride on when the wheel's tire passes over the point of the frog, and a tiny bit of "drop" is fine, and won't affect performance or appearance at all.I build my turnouts to these "tight" specifications, and I run quite a few sets of FVM Narrow Tread Lo-Pro wheelsets without any problems whatsoever on any of the hand-built turnouts on my layout.I haven't noticed any "wheel drop" on my turnouts on my layout, nor on my test module, which has Micro Engineering #6's, so I decided to take a very close look at cars with different wheel widths rolling over my "tight" turnouts.I was surprised by what I found. Every car that I run on my layout has lo-pro wheelsets...some of them have the original MTL Lo-Pro plastic wheelsets, some have the later version, some have NWSL Lo-Pro metal wheelsets, some have FVM Lo-Pro metal wheelsets, some have FVM Narrow Tread Lo-Pro metal wheelsets...and every car that I have drops their wheels into my frogs. They also drop into Atlas55 turnout frogs, Peco55 turnout frogs and Micro Engineering Code55 #6 turnout frogs. Every one of them "bumps" a little when they go over these frogs...especially when I am pressing down on the car with my finger. They "bump" much less on my "tight" turnouts, but...they still bump.I have one old test car that has pizza cutters and extra-wide metal wheels on brass axles that I thought I'd try....and it "drops" too!...even with extra wide wheels."What's going on here??" I thinks to myself. Okay...what's going on is that the wheels' tires are tapered, being a larger diameter at where the flange starts and a smaller diameter at the outer edge of the wheel. When passing over the point of the frog, even if the tire is wider than the space where the frog point ends and the closure rail begins, the smaller diameter on the outside of the wheel drops down onto the wing rail (right before the sharp bend in the rail) and climbs back up onto the closure rail as the wing rail gets closer to the bend where it turns into a closure rail.The distance that all of this happens in is very small, but larger as the size of the turnout increases...but still really small.There's not much that can be done about this in N-scale due to various flange heights and the wide flange width, with dictates the width of flangeways and also the "check gauge" on each wheelset from the inside of the left flange to the outside of the right flange. This distance is what dictates the "track check gauge" measurement standard for NMRA compliant N-scale turnouts.If you were having this problem on a RTR turnout I'd say to use shims to fix it, BUT, since it's on a hand-laid turnout, you should be able to fix the problem using your iron, a tweezer, your NMRA N Standards Gage and maybe a little flux...and moving your rails at the frog so that the clearances become "interference" clearances...which won't completely eliminate wheel droppage for FVM Narrow Tread wheelsets, but will minimize any problems.For me, since I didn't notice "the problem" before today, I'm not going to worry about...but just continue to build my turnouts to "tight" NMRA Standards as I have been for the past couple of decades, 'cause it works for me.Photo (1) - FVM Narrow Lo-Pro Wheelset sitting on the frog point on one of my "tight" NMRA Standard #11 turnouts:Photo (2) - FVM Narrow Lo-Pro Wheelset Dropping Into My #11 Frog:Photo (3) - FVM Narrow Lo-Pro Wheelset Having Climbed Out of My #11 Frog:Photo (4) - FVM Narrow Lo-Pro Wheelset Completely On Top of Railhead On Closure Rail On My #11 Turnout:Hope this helps.Yes...my photos are vertical...I'll fix 'em after dinner tonight.Cheerio!Bob Gilmore
Bob: Tapered treads are why one can also hear a "clunk" when the prototype goes over a frog!
Are N scale treads tapered though? Some are, some aren't?
Richard Feynmann explaining tapered wheels:
Don't forget the role of the guardrails opposite the frog as well. The one time I had trouble with FVM wheel operation through a FastTracks turnout was when I had overwidened the guardrail flangeway in an attempt to adjust something else. It allowed too much pivot slop and created a derailment risk for the FVM wheelsets.
Craig:I just caught up on this thread. The problem is the turnout guard rails are in the wrong place. I do not believe these were built correctly and I use fine scale FV wheels without any issues on #10 turnouts. I just checked my FT#10 turnouts, and the middle of the guard rails lines up almost exactly with the point of the frog. Your guard rails are not into play when the wheel is almost at the frog. Try moving the guard rails so that they are actually in play when the wheels get close to the frog, that should cure the problem.Take a look at any FT turnout diagram, you will see the guard rail middle lines up with the frog point. I have attached a FT curved turnout template, look at how the very point of the frog lines up with the middle of the guard rails, which yours do not - so the guard rails are not doing their work when the wheel hits the frog.Hope this helps.Kind regards,Bill
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Topic: Hand laid Fine N scale turn out standards / tools / solutions? (Read 3407 times)
