Do wheel flanges touch the bottoms of Turnout Frogs?

Model Railroader General Discussion (Model Railroader)
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In 1:1 railroads, do wheel flanges “bottom out” in turnout frogs?

I’m working on handlaying turnouts, and it seems obvious that I need to fill the frog with solder, and create a clearance equal to the wheel flange height.

In Tony Koester’s Dec 1989 article on turnout construstion, he says to cut the flange clearance in the fog with a hacksaw blade, “just deep enough to clear the flanges, so wheels will ride on the bottom of the flangeway and not drop into the gap at the point of the frog.”

He continues to say, “This won’t work if your equipment has flanges of various depths.”

So the question is, what do real railroads do?

Do most model railroad turnouts just have overly deep flange clearances so that different equipment will run on them?

My goal is to have “click-less” turnouts, if at all possible. I’m going for smooth as glass here.

It seems the wheel needs to dip down into the frog, the flange bottoms out, then the wheel itself rides up onto the sharpest point of the frog. The smaller the distance it has to ride up, the less click you’d have.

Thoughts?

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Real railroads have a 1" flange depth. If all of your wheels conform to NMRA RP25, then you should have a flange depth of .025", IIRC. Check out the NMRA web site. That said, most comercial turnouts have something a little greater that that. With various wheelsets, and dirt/crud - You may have to plan for a greater depth. You do not want the wheels to ‘ride up’ through the frog either!

Jim

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In the pic below you can see that there is dirt in the frog. But that is far from a heavy traveled line. Now on the mainline the flanges have wore deep smooth groves at the bottom of the frogs. I will post a closeup pic of them tomorrow.

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So, theoretically then, you’d want different flange clearance depths in your Frogs if you use lower profile flanges, right?

Very interesting.

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Question?
On a Real Railroad. Why are the Frog Points always chipped.
Allan.

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a. Wheel franges are not supposed to touch or ‘ride’ in the bottoms of the frog 's flangeway.

A CORRECTLY placed guard rail not only pull’s over the oncoming wheel, aligning it, but suspend’s it while crossing the gap. It work’s, as anyone who has spiked an old Anderson (or new BK) turnout kit will tell you. Wheels go through with scarcely even a ‘click’.

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Don, I don’t understand how the guard rail would suspend the wheel - because the guard rail is inside the wheel, right? Just trying to understand what you mean.

I guess if the truck could be considered a perfectly rigid body, the other three wheels would define a “plane”, and the wheel going over the frog would be suspended.

I have no idea how rigid “real” trucks are.

Just trying to understand how this works - I always thought Frogs were fascinating.

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I have not seen flange-ways shallow enough to lift the wheels on their bottoms except where the rails have been pounded down and not replaced as they wear. Normally, the wheels should ride on their rolling surfaces all the way through the frog.

The trucks are quite rigid, but their mountings permit rocking via the springs. Hence, the swaying reefers and box cars.

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A properly gauged guard rail ‘holds’ the wheel in alignment when going through the frog and prevent’s ‘dropping’ into the gap. I don’t recall if it’s due to the rigidity of the truck or the 3 point suspension, but it works. As for “smooth as glass” turnout’s: anyone spiking Anderson designed BK turnout’s in-place using the NMRA gauge will tell you this. The key I guess is tighter tolerances and spacing than available in prefab’s.

With .88 wheels I heartily recommend you the BK kit’s. I’ve tried a lot of turnout’s and these were the smoothest. Gone were derailment’s.

http://www.troutcreekeng.com/bkho.html

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Thanks guys, I’ll be handlaying my turnouts (which is why I’m trying to get a really good understand of what’s going on in the Frog).

There is definately a moment where the wheel passing through the frog is either suspended in air, or dips down and its flange bottoms-out. It has to do either of those (or somewhere in between).

It can’t just ride on its rolling surface, because for an instant, it crosses an empty “canyon”. For an instant, there is no rail for the rolling surface of the wheel to ride on.

So I’m trying to understand what exactly is going on there.

For example, if the flange bottoms out, I’ll pay more attention to the depth tolerance of the flange gap there. The NMRA gauge just gives you a minimum depth - not a max. So I’m trying to figure out my max depth.

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THE MORE I THINK ABOUT IT - only a single wheels is over the gap at any instant. 3 wheels are always on solid rail at any given time.

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Yes Don, that’s exactly what I meant when I said …

"I guess if the truck could be considered a perfectly rigid body, the other three wheels would define a “plane”, and the wheel going over the frog would be suspended.

I have no idea how rigid “real” trucks are."

So, if the trucks were infinitely rigid (i.e. didn’t flex at all) which of course isn’t realistic, then the one wheel would hover over the gap no problem, without dropping down at all.

But of course, they do flex, so that wheel drops down some. How much? That, I don’t know. I don’t know if it’s a lot (i.e. enough for the flange to bottom out), or just a tiny bit.

And in reality, our model trucks probably behave differently than real life trucks do.

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I googled and found this article on the subject:

http://calbears.findarticles.com/p/articles/mi_m1215/is_n6_v196/ai_17040466#continue

It appears the wheel does jump and slam into the frog. That is, it is not supported by the flange.

Interesting - it mentions something I didn’t think about - if the flange rode on the frog, it would be a different effective radius than the other 3 wheels. This means there is going to have to be some slipping for sure, because the wheel that would ride on the flange would start to spin at a different speed than the other wheels.

I eat this stuff up. From what I’ve found on my “google research”, in “real life”, the wheels don’t ride on the flanges.

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EDITED
A rail wheel should ONLY ride on its tread NEVER on the tip of the flange.
You may not realise that the wheel section is part of a cone… put another way the tread is NOT flat. Similarly the railhead is a curved shape. To a degree rails are also canted in toward the four foot way… don’t know the exactly how this is done in modern track … in older UK track the rails were held tilted in by the design of the chair.

The physics is… in LAYMANS terms… if you glue four equal cones base to base and set the two double cones parallel in a rigid frame and then place the “truck” on two rails they will waddle down the tipped rails until they even out as a pretty much straight line. if you cant the rails to the correct position the frame and cones will run in a straight line.

trouble then is to get the thing to go round curves NOT straight on.

So what happens in a rail vehicle truck and track combination is a compromise. There’s 150 years and more of research into the outcome and they’re still working on it.

A switch is a combination of a straight track and a curve or two curves. Diamonds are two straights. Which brings in the point that the frog is in fact two straights at angles to each other. Where the angle is very shallow as in high speed trackwork the common crossing/frog as well as the blades is switched. The componenets are moved to close the gap. this prevents a wheel taking the wrong side of the crossing. this is also what the gaurd rail does… the guard rail DOES NOT support the wheel… it can’t… there would have to be an inside flange. Also, if the guard rail were steering the wheel you would see wear, a high shine like on the railhead, or chafing on the inside of both the wheel flanges and the guard rail.

So what’s the guard rail there for? Most of the time (like the pilot of a modern jet) nothing… they are there to do what they do when things go wrong. On the few occasions a wheel gets deflected out of

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If your turnout is built to the correct standards for your wheels (either NMRA or Proto in most cases) and your turnouts are #8 or smaller, than the frog gap is too small for wheels of even small diameter to “drop” into. Only the very long, low angle frogs have gaps wide enough to worry about - assumes everything is correctly gauged (at the narrow end for HO).

The technique of filling the frog with solder and “sawing” it out (I use this technique myself) is an effective modeling technique - not prototypical - to build good performance, custom frogs in place on the layout. However, to allow older deeper-flanged equipment - or even steam pilot and trailing wheels on newer stuff - to run through the frog, it must be sawed out deep enough for those flanges. This means normal flanges will not ride on the solder filler anyway.

After studying pictures of the prototype, I have been reducing the soldered filler (sawing out more), especially in length. That way the filler more closely represents the filler blocks on the protoype. Same with guardrails, I have been reducing their length to what is actually needed to guide the wheels through the frog.

I personally don’t like (but many others swear by them) PC board ties because of the difficulty in matching my wood ties. I only use PC board for the throwbar, and I am experimenting with moving that underneath the ballast like some British Proto modelling efforts I have seen.

Again, experiment, and do what you enjoy and brings you pleasure. For more information, there is an active handlaid track Yahoo group you may want to check out.

Fred Wright
Chief Engineer, brakeman, and jack of all trades…you know the rest
Picture Gorge and Western Railway - “none more picturesque!”
Tillamook Head and Bethel Railway - “to Heaven and back”

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David and Fred,

Thank you very much for the tips!

David, it sounds like this is a subject you’re quite familiar with. (And I suspect you’re a mechanical engineer based on the words you use).

Yes, I have recently looked at an “old fashioned” frog in front of an old relocated and restored SP depot, and sure enough, there was no frog casting. It was just made of rail, just like my handlaid turnout in the garage!

Alright then, I think I’ll skip the whole filling up a puddle of solder than cutting through it with a hacksaw blade in order to have a frog that looks like a prototype frog casting. I think that step just adds complexity for me - soldering all that puddle without burning ties, cutting through it with a hacksaw blade and filing it, all that mess. I think I’ll just skip it. I’ll be spiking into Pine, so I don’t think I’ll have to worry about my spikes moving.

As mentioned, my handlaid frog does work without it the simulated frog casting made from solder, but if I push down on the truck over the wheel going through the frog, I could make it click - which made me wonder if I should prevent this by having the flange help it out, which got me thinking about real life frogs…

I bet if you reached in with a giant’s finger and pushed down on the truck of a “real” truck right over the wheel crossing the Frog, you’d get more of a click also.

Very interesting info David. You gave me some more things to ponder that I didn’t think about (just for fun, that won’t affect my turnout construction any…)

As for handlaying

I’m trying to figure out a foolproof way to make turnouts. I like Tony Koester’s article in Dec 1989 MR, but his method of frog location seems sort of trial-and-error-ish. He lays the “straighter” of the main outside rails first, then locates the Frog. I think I’ll be starting by locating the Frog first.

I want to build them in place on the railroad, but now I’m starti

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Hi All,

I have been following this thread with interest and thought I might be able to contribute something to the discussion. The handlaid turnouts I built early on I always used the “fill the frog technique”, more for mechanical reasons than to prevent wheel drop in the frog.

I no longer do this, as I find it is a messy step that can actually cause more jumping around as wheels pass through the frog. Flanges on wheels are not standardized, and do vary from one manufacturer to another and if enough solder is not removed, the wheel flange can roll up on the solder and cause just as much grief. I found I was removing enough solder to clear all the flanges, and therefore the solder in the frog was serving no purpose.

Like mentioned earlier in this thread by others, if a turnout is built to accurate NMRA standards, and ALL your wheelsets set to the same standards, the width of the tread of the wheel will span any gap in the frog area and you will not get any wheel drop. No need to fret over where the track gauge ends up, as long as it is within specifications, you will have no problems.

What I have found over time is the most critical, important element in getting a turnout to run smooth, without any bumping or wheel drop in the frog, it to produce the longest, sharpest frog point as possible. This will get the point far down into the throat of the frog and allow the wheels to get onto solid rail as quickly as possible. Spend time here and you will have success.


A #8 curved turnout in HO scale on wood ties


#4 crossover, handlaid on dock

Recently we wrote a very thorough document on hand laying a turnout, curved or straight, on all wood ties. These are the instructions for our “TwistTies”, laser cut flexible wood turnout tie strips, however, all t

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Thanks for chiming in Tim!

Your turnouts are quite inspiring (as was your layout featured in MR a few years back). The quality you achieved on this small layout was part of the inspiration for a module-sized layout I’m currently planning.

Tim, what are your thoughts on using semi-scale wheels? I’m wondering if I should go with semi-scale wheels, or just forget about it and use all RP25 wheels.

The big question is if I go with semi-scale wheels, should I be designing all my turnouts to fit semi-scale wheels? The NWSL wheels have a .005" narrower flange than RP25. I’m thinking the .005" won’t be a big deal, but I really don’t know. It may allow more dropping into the Frog, etc. It will definately allow the truck to turn more and get out of alignment as it goes through the frog, but practically speaking, I don’t know if it will be a big deal or not.

That PDF is great too. Thanks!

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In my opinion I would not use them. Speaking purely from a design point of view, once you start changing the standards of one item, it will start a chain reaction that can be difficult to stop.

Again, this is my opinion, as others may have had different results and priorities, the pay-off of using semi-scale wheels is not worth the investment. The thread thickness is a critical dimension in the NMRA standards, and is critical to the wheel drop issue on turnout frogs. The width of this thread allows the wheel to span the gap in the frog by partially running on the wing rail prior to the wheel rolling onto the frog point. All these areas work in unison. If you remove part of the thickness of the wheel thread, it increases the chances of the wheels dropping into the gap. To fix this the gauging of the flangeways needs to be tightened up, and this will start to effect other aspects of performance. Before you know it you have started the chain reaction.

If you like to tinker, or find the width of the wheel threads to be a very distracting issue, then the effort put into semi-scale or Proto:87 will be worth it for you. I believe modelers really just want to get the trains rolling as reliably as possible, and actually get their layout finished, me included.

At the end of the day, like everything else in model railroading it is all about preferences and priorities.

Thanks for the kind comments about the layout, I am surprised anyone remembers it being in the magazine, since it was almost 10 years ago now.

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Hi again!

I tried to edit my last but it suddenly vanished into cyber space. So when I’d finished saying “Oh bother” I went to bed. Anyone know why I lose edits and answers like this?

Any way… I’ll edit above again and waffle on a bit more here.

I’m a railwayman but my Dad was a mechanical engineer. I’ve also looked through most of journals such as “The Engineer” from issue 1 to c1950. One of the things this taught me is that the debate as to what to call a “frog” has been going on in professional circles at least since the 1880s. The engineers called it a frog back then… or said you shouldn’t…
Thing I want to comment on here…

“It will definately allow the truck to turn more and get out of alignment as it goes through the frog, …”

This isn’t going to happen … if you build your track right and put your cars together sensibly.

Remember you have the TWO elements here NEVER just the one.
TRACK
CAR / LOCO (Wheelsets in frames)

It’s no good blaming your track if your cars / locos are wrong and vice versa.

NOW THEN…

THE THING TO DO FIRST IN THE TRACK IS…

Build it like the prototype

1, physics is the same it does not get scaled to 1;87 1:48 or whatever. This applies in all three directions plus movement.
The only thing that changes between model and real is the weight because we don’t scale that. Empirical evidence suggests that this makes our lives a whole lot easier. Seeing as our trains don’t float away from lack of weight we appear to be on the winning side. (UK models are usually far lighter than US… personally I would go with this but to save time and effort… and to maintain compatibility… I stick with as-it-comes / NMRA weights).

  1. As I said … the common crossing is TWO STRAIGHT RAILS AT ANGLES. This is why the truck “ain’t never gonna turn” … unless there is something wrong with it, with