# Switch frog groove depth



## CliffyJ (Apr 29, 2009)

When going through a switch or crossing, are the wheel flanges supposed to be riding on the bottom of the frog? 

I've got a Hartland 4-4-0 with flanges up to 3.2 mm, going through frogs right at 3.0 mm (the NMRA standard). 

Oddly, that standard cites 1.68 mm as the min frog groove depth, but my LGB and Bachmann mostly exceed that (but no more than, say, 2.9 mm in a quick survey). 

The reason I'm bring this up is that my 4-4-0 noticeably bumps over the frogs, and it looks plain weird. 

Does anyone else run into this? 

In case you're interested, here's the NMRA standards I'm referring to:
Track: http://nmra.org/standards/sandrp/pd....02.24.pdf 
Wheels: http://nmra.org/standards/sandrp/pd....02.24.pdf 

===>Cliffy


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## Garratt (Sep 15, 2012)

On some model turnouts the flanges are supposed to ride in the bottom of the frogs unlike on a prototype turnout.
It is because the degree of the frog is much greater than a prototype turnout which leaves a gap where the tread can't be supported by either the point or wing rail therefore the wheel rides on the flange in the bottom of the frog.

Depending on flange and frog depth sometimes the flange will ride in the bottom of the entire frog and sometimes it will only do this where the tread can't be supported by either the point or wing rail. 

This illustration from nmra.org should help to understand the issue. 










Andrew


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## toddalin (Jan 4, 2008)

Use care if you try to "lower the groove" because some turnouts will not operate properly with some equipment once this is done.

In some cases, such as on the AristoCraft 10-foot diameter turnouts with heavyweight coaches, as the wheel rides up, it helps route the railcar to take the diverging path. If you file the groove, the railcars now bump into the frog and derail when you select the diverging path. The cure is to put a brass strip along the guard rail of the diverging path to pin the wheels in place.


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## CliffyJ (Apr 29, 2009)

Thanks for the responses guys. 

My switches have plastic wing rails that are slightly lower than the rail tops, which is further resulting in some wheels dipping while going through, even though others (my HLW drivers) are bumping up. Thanks for the figure Andrew, it helped me visualize what was going on. 

Point taken Todd, I'll not deepen the grooves. I think I need some replacement drivers for that 4-4-0. Or, let it sit as another "shelf queen." 

===>Cliffy


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## East Broad Top (Dec 29, 2007)

Todd's "fix" to the problem encountered when grinding out flangeways is precisely how a switch is supposed to work. That's the purpose of the guard rail--to keep the wheelset far enough to the outside of the switch where the flange on the inside doesn't come in contact with the tip of the frog. (This distance is called the "check gauge.") If your wheels are touching the guard rail and still hitting the tip of the frog, either the gauge of the wheels is too wide or the distance of the flangeway on between the guard rail and stock rail is too wide. In the case of wheels being gauged too wide, you can usually narrow the gauge a few thousandths to compensate. Where the distance of the flangeway is too wide, a shim as Todd describes on the guard rail (between the guard rail and the stock rail) will help. Most commercial switches from LGB, Aristo, USA, etc. have flangeways on this part that are unnecessarily wide and can stand to be shimmed .010" or so. 

With properly-shimmed guard rails keeping the check gauge in spec, you should be able to grind away the base of the frog so your deepest flanges ride through without bumping. The trade-off is that if it's a switch where cars must ride on the flanges to go through, then maybe your deepest flanges will no longer go "bump," but your shallower flanges will. Pick your poison, in that case. 

Later, 

K


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## aceinspp (Jan 2, 2008)

Fixing guard check does not fix the flange way depth of a frog. Frogs are either flange bearing or non flange bearing so if your loco flanges is touching the flange way you are now on a flange bearing frog. You may or may not be able to deepen the flange depth. It depends on how the switch is made. In some cases the point of frog is not at its theoretical point and in this case the wheel will drop before making the transition to the wing rail. One should check to see how you loco is transitioning from the frog to the wing rail. I would roll a car over the frog and observe if the wheels drops or does not. If it does not drop then you can make the flange depth deeper to make the loco run smoothly through the switch. Later RJD


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## Garratt (Sep 15, 2012)

The car and loco are likely to have different flange depths though. If all flanges were the same depth an ideal frog depth could be determined but they aren't. It sounds like Cliffy's HLW loco has much deeper flanges therefore excessively bumping up and riding on the flange all the way through the frog. In the case of flange bearing frogs ideally a wheel should bump up very little or perhaps drop very little on the rail transition. It is when there is a great difference between flange and frog depth that there are problems. The wheel tread width and taper has an effect on the transition too. 

Andrew


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## Dan Pierce (Jan 2, 2008)

If it is only the one HLW, then being an engine I would file/grind/sand down the flange.


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## CliffyJ (Apr 29, 2009)

Posted By CliffyJ on 17 Aug 2013 06:18 AM 



... Oddly, that standard cites 1.68 mm as the min frog groove depth, but my LGB and Bachmann mostly exceed that (but no more than, say, 2.9 mm in a quick survey). 


===>Cliffy 

I should have said "max flange depth," not "min frog groove depth". Sorry for confusing things further.

Also, those links I pasted don't seem to work, I'll try again:
Track:
http://nmra.org/standards/sandrp/pdf/S-3.2 2010.02.24.pdf
Wheels:

http://nmra.org/standards/sandrp/pdf/S-4.2 2010.02.24.pdf


Thanks for all the further info guys. I have to confess that my head is spinning! So much to learn.
For now, I'll probably grind the drivers down a bit, or take the decoder out of the 4-4-0 and put it in an LGB mogul.


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## Garratt (Sep 15, 2012)

Yeah, I thought that was a bit small. I thought the min frog depth was 3mm same as max flange depth. Which means they are never perfectly flange bearing, except for the transition. I would just do as Dan suggested and finish your HLW locomotive flanges down, maybe to the same as your frog depth of 3mm. It would then theoretically neither bump nor drop. Making your flanges deeper will make your car wheels drop even more than they already do. My LGB cars have flanges about the same as the LGB frog depth. My Bachmann cars all drop though. Dropping wheels create impact and can wear the rail points. What does one do though? Not all wheels are created equal. 

Andrew


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## Greg Elmassian (Jan 3, 2008)

Amplifying RJ's response, and pointing this at Kevin mostly.... it's not just the guard rail, and "not properly shimmed" is how I would state it. 

1. proper guard rails, both level with the top of the rails AND of proper flangeway width... 

but the main reason I am commenting, is that most model frogs are built with bad geometry, improper wing rail flange widths and also the geometry of the point of frog is bad. 

Many turnouts have been modified to allow wide ranges of back to back settings, and overly thick flanges, not to mention overly deep flanges. 

LGB made all their flanges the same depth (pretty much) and flange bearing frogs... everything works well until you use a different wheel contour, back to back, or flange depth. 

So, if you are trying to follow standards, and get wheels without toy like flanges, you will have to be prepared to modify some things. 

I will say that after modifications, my Aristo WR switches are smooth as a baby's butt... there's not as good a result on their #6 because the frog geometry sucks. 

Greg


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## East Broad Top (Dec 29, 2007)

Greg, can you draw a picture of the "bad frog geometry" you're talking about? Is this a frog point that's too blunt, or out of line with the rails, or ??? 

Later, 

K


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## CliffyJ (Apr 29, 2009)

I appreciate the education on what the guard & wing rails are for.

I've noticed a couple of things on mine, first, judging from the figure Andrew posted, the wing rails seem a little incomplete. 










The plastic in the wing area that the tread is supposed to ride on is about .02" lower than the rail. So rolling a truck across it, one sees the wheel dip at that point. 

If it all were at the same level, and the wings were complete, I can see how the wheels would be supported throughout. And that pretty much answers my initial question. 

As for the guard rails, in parallel with what's been said here, NMRA RP-13.5 says: "The purpose of the Guard Rail is to guide wheels thru the desired side of the frog without splitting the frog point." That's not quite happening with my switches. Especially on the diverging leg, a wheel sometimes runs smack into the tip of the frog. 

Before this thread, I was considering grinding away some of that tip. Now I realize that would make the "dipping effect" worse. 

So now I'm interested in the shims that Todd and others have spoken of. How do you make it stick to a plastic guard rail? Any pics? What about solvent-bonding on some compatible plastic (ABS?) strip instead?

Thanks,

===>Cliffy 

PS, I should mention that the prototype I'm striving for (V&T) used mostly 4-4-0's and 2-6-0's, so that's why I've been testing with this 4-4-0 as a "worst-case."


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## toddalin (Jan 4, 2008)

Posted By CliffyJ on 18 Aug 2013 10:44 AM 
worse. 

So now I'm interested in the shims that Todd and others have spoken of. How do you make it stick to a plastic guard rail? Any pics? What about solvent-bonding on some compatible plastic (ABS?) strip instead?

Thanks,

===>Cliffy 

PS, I should mention that the prototype I'm striving for (V&T) used mostly 4-4-0's and 2-6-0's, so that's why I've been testing with this 4-4-0 as a "worst-case."


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## CliffyJ (Apr 29, 2009)

Thanks Todd! 

So no glue, screw or nuthin? And the backside of the wheels don't tend to scrape the shim upward?


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## Greg Elmassian (Jan 3, 2008)

Cliff, first, get the guard rails right... then get your back to back proper on your wheelsets.. without doing both, you are spinning your wheels. 

I'm in agreement with your observations on the Train-li frog. 

Kevin, point of frog, height of frog, wing rail flangeway width, it's different on every one. The #6 Aristo has the theoretical point of frog in the wrong place, way too big a gap in the throat. 

Greg


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## CliffyJ (Apr 29, 2009)

Posted By Greg Elmassian on 18 Aug 2013 12:35 PM 
Cliff, first, get the guard rails right... then get your back to back proper on your wheelsets.. 
Greg I'm gradually getting it. "Back to back" is the NMRA dimension "B" for wheels, and now I'm seeing why they didn't begin with "outside-to-outside," or even cite that dim as ref. So that means that the outer guard rail face is pretty critical. Sorry, just talking out loud to myself, as it were.

Do you shim your guard rails as well?

===>Cliffy


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## Randy Stone (Jan 2, 2008)

I have the Aristo Craft Wide / 10 ft dia turn outs in SS. After replacing the frogs with the new improved versions, I found some locos (Don't remember which ones, sorry) and some frt cars (Don't remember which ones, sorry) literally jumped when entering the switch from the short end of the switch. What I found was that the ramp angle of the frog was too abrumpt. After lengthening the ramp by lowering the initial point of entrance and grinding down the inner part of the ramp, I have not had any problems with derailing. I don't have any Aristo Craft heavy weights, but I do have USAT passenger cars, a Dash 9 along with various other frt cars and locos.


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## CliffyJ (Apr 29, 2009)

Randy, sorry for not knowing the proper terms, but by "ramp," are you describing a gradual filing or grinding of the tip of the frog downward? Or something else?


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## toddalin (Jan 4, 2008)

Posted By CliffyJ on 18 Aug 2013 12:33 PM 
Thanks Todd! 

So no glue, screw or nuthin? And the backside of the wheels don't tend to scrape the shim upward? 


Nope, no nuthin'. The fit is too tight for the wheels to lift.


From George Schreyer's web site:

Todd Brody found that he could reface a plastic guard rail by bending a 1/64" thick by 3/32" wide brass strip around it as shown in the photo. He found specific instances where this improved tracking. This does get rid of the glue problem, and the piece is removable and replaceable. Note that brass strip is usually die cut such that the edges on one side are rounded and the edges on the other side are sharper. The rounded edge should be the one facing the wheels.


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## CliffyJ (Apr 29, 2009)

Eeeyecellent Todd. So you just cut the lengths, and crimped with needlenose pliers, huh? No JB Weld, no Magic Monkey Poo. 

I'll have to try now. I think I just bought 14 feet of the stuff... but it was only $11, and it's always good for detailing something. 
http://www.amazon.com/Flat-Bar-64-3...1376857683

===>Cliffy


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## Greg Elmassian (Jan 3, 2008)

Crimping works pretty well, the plastics that the switch frogs are made from does not like glue, and many glues don't work well in sunlight. 

The shims WILL move though, so I make mine "wide" enough so that they contact the ties when in place. 

Cliff, did you read my pages on track and wheel standards? The NMRA does spec gauge, check gauge and back to back. The biggest problem in derailing in switches appears to be points not fitting well to the stock rails or picking the point of the frog. 

Greg


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## Garratt (Sep 15, 2012)

Cliffy although the LGB turnout's wing and closure rail join design is different to your train Li turnout, the LGB also drops down off the brass rail to the plastic wing rail.
Many turnouts including AristCraft, LGB and Peco all have parts around the frog area that sit higher than the outside stock rails. This can cause power pickup problems with stiff 2 axle locos. 

It seems some flange bearing frogs are designed to bear the flange mainly on the transition but on a LGB R5 there is a metal conductive strip in the bottom of the flange bearing frog which is shallower than most. 

Image to illustrate the role of the guard or 'check' rail. 
NMRA S-1 Overview of Scales Track & Wheel Relationships










Andrew


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## CliffyJ (Apr 29, 2009)

(another crashed message, so the really short version is here) 

Cool, thanks again guys.
Greg, I'll have to read your article on this, thanks for the reminder.


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## Greg Elmassian (Jan 3, 2008)

It may take a while, but once you understand how this stuff works, then it's pretty straightforward to analyze the switches you have and see what is wrong. 

Also, get a single wheel set, and make it terribly under spec on back to back... roll this single wheel/axle through a switch and see what happens... 

Here's bad under spec:


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## CliffyJ (Apr 29, 2009)

Great shot, Greg, clearly demonstrates the "back to back" sub-dimensional affect. 

Yesterday, as we were all confabbing on this, I took a single truck and ran it across a TL frog, and an LGB frog, twisting the truck, to understand better what the guard rails were doing. In the TL test, the truck's wheels hit the frog point. LGB, couldn't do it. That was my big Aha, immediately followed by tracking down that batch of cheap K&S brass strip -- just like Todd recommended. 

As an aside, it's threads like this that I wish I could rename the title of.... only because what I thought I was asking turned out to involve quite a different problem and solution! 

Thanks, 
===>Cliffy


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## Randy Stone (Jan 2, 2008)

Cliffy 


When the wheel comes to the frog, it touches the frog and rises up as it travels towards the middle of the frog. This should be a smooth transition. But the wheels were hitting the square end of the frog instead of the grooved area of the frog. Thus the wheel would jump. To cure this, the entrance on to the frog had to be lowered and then the length of the ramp had to be lengthened so the ramp wasn't too steep


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## CliffyJ (Apr 29, 2009)

Greg, I just read your article on switches. Excellent! 

Interesting how you ended the section on frogs: 

Read the last sentence over again, and if you do not get it, go get a single wheelset and roll it through a frog and try to make it go the wrong way, you will see the back of the wheel is bearing against the guardrail. 

That's exactly what I did. And though what I was reading from here and NMRA.org all made sense, that simple demonstration said it all. Like you say, the (properly positioned) guard rails are the ONLY thing keeping the wheels on course. 

Nicely done, 
===>Cliffy 

[post attempt #11... this is getting old... I'm hating the spinning thingy... need bigger foil hat... wow, just broke my record of seven attempts... and again... I should get a prize by now... must get credit for the effort...]


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