# Switch frog question



## traction fan (Oct 5, 2014)

I'm asking for answers from people with experience working for a real railroad. My only connection to railroading is strictly the model variety. 
I've only seen real switch frogs from a distance and some time ago. I seem to remember that the flangeways were about 1" deep. I have also read that prototype wheel flanges are about 1" too. 
My question is, are frogs and wheels designed to let the wheel's flange bear some of the weight of equipment while a wheel's tread surface is not supported by rail; as when passing through the open area of the frog?
Commercial, model turnouts have flangeways that are deeper than most model wheel flanges. They let a wheel fall into the open area of the frog, and then be bounced back up when the wheel tread hits the frog's point. If this happens on a full-size railroad. I would think the wear on frog points and wheels would be excessive. While riding as a passenger on Amtrak, I do feel, and hear, some vibration when passing through a switch, but nothing as severe as what I think would happen if real frogs were made with flangeways as deep as model ones would be if scaled up to full size.

Traction Fan:smilie_daumenpos:


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## Ace (Mar 30, 2016)

I have worked for actual railroads but it has been some time ago. I was issued a wheel gauge and we were expected to watch for wheels with defect conditions: thin flange, worn tread, shelled tread, heat cracks (from braking), bearing problems, etc. Got to see the wheel true machines in the loco shop up close.

The standard flange depth is 1 inch.

Just recently I happened to be researching some of the newer switch designs and learned about "flange bearing frogs", which are intended to eliminate or minimize wheel drop and impact loads at frogs. It helps to the extent that wheel flanges are within spec on the flange depth. These are a newer development for freight railroads, not standard.

This link provides a good overview. Use some of the key words to find more info.


_https://en.wikipedia.org/wiki/Flange-bearing_frog

Several types of flange-bearing frogs have been developed for specific applications on North American railroads. These frogs may be flange-bearing in one or both legs of the frog, and may by used either as part of a turnout or as part of a diamond.

Lift or jump frog
Combination tread- and flange-bearing frog
One-way low-speed diamond frog
Full flange-bearing diamond frog_


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## Ace (Mar 30, 2016)

I used several old AHM/Rivarossi #6 switches on my HO yard extension project some years ago. I noticed that the wheels dropped noticeably going through the switch frogs. All of my HO equipment was Athearn or MDC with RP25 wheels, but the switches were made for those old oversize flanges. I found that I could fit pieces of thin plastic in the bottom of the flangeways of the frogs to minimize wheel drop and allow trains to roll through the switches more smoothly. Ideally, if model wheels and trackwork are done to precise standards, flange-bearing frogs would improve model railroad operation through switches and crossings.

Wheel drop is worse with models if you use narrower wheels closer to true scale width. If the wheel tread is flat and wide enough it will bridge across the frog flangeway gap. Actual railroad wheel treads have a conical profile (exaggerated in this graphic).


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## mesenteria (Oct 29, 2015)

Not only are our frog angles incredibly sharp, but they allow wheel drop unless the frogs are filled...which is often the case. Tim Warris over at handlaidtrack.com (fastracks) demonstrates the problem in a video on his site and explains why his frogs, if manufactured correctly, actually allow the tire surface to bear all the way through his frogs. The guards around the frog point share the burden for a few tenths of an inch.

I have yet to see a model frog that is flange-bearing, but it doesn't mean someone won't we showing us how to do it before long. Maybe even Tim Warris since he's a guru with hand-laid turnouts.


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## traction fan (Oct 5, 2014)

*Flange bearing frog on an N-scale turnout*



mesenteria said:


> Not only are our frog angles incredibly sharp, but they allow wheel drop unless the frogs are filled...which is often the case. Tim Warris over at handlaidtrack.com (fastracks) demonstrates the problem in a video on his site and explains why his frogs, if manufactured correctly, actually allow the tire surface to bear all the way through his frogs. The guards around the frog point share the burden for a few tenths of an inch.
> 
> I have yet to see a model frog that is flange-bearing, but it doesn't mean someone won't we showing us how to do it before long. Maybe even Tim Warris since he's a guru with hand-laid turnouts.


mesetena;

Thank you for the information, I didn't know whether a prototype frog supported the wheel flange or not. From the answers received, it would seem that they did not. until recently and on a limited basis.
Since you have not yet seen a model turnout with a flange supporting frog, I'm attaching a photo of an N_scale turnout with such a frog. 
I build my own turnouts, and make the flangeways (both frog, & guardrail) the depth of the measuring tabs on the NMRA gage. With low profile wheels, this lets the wheels ride on their flanges. The movement through such frogs is super smooth.

Again, thanks for the response;

Traction Fan:smilie_daumenpos:


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## traction fan (Oct 5, 2014)

*Thank you*

Ace;

Thanks for all the info on real turnout frogs. As for your experience with the older Rivarossi wheels dropping, I've seen a lot of that in N-scale too. The frogs on Atlas, Peco, and Walthers/Shinohara, N-scale turnouts all let wheels drop right down into them. When I make my own turnouts & crossings, I keep the flangeways shallow. This gives an exceptionally smooth ride through their frogs. I had assumed this might be the case on the prototype. Yet another of my assumptions proved wrong!:smilie_auslachen: (my wife of 35Yrs. keeps an extensive list of them!:laugh

regards;

Traction Fan:smilie_daumenpos:


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## dinwitty (Oct 29, 2015)

most model trucks are not flexible like the prototype, the springs do not work and as the truck crosses the frog, the stiffness will not quite drop the wheel down. But we do have trucks sprung, and early model trucks have working springs with a fully flexible truck. Prototype frog points are usually one piece castings. Full frogs may be an assemblage of parts. There may be some flange supporting.


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## Old_Hobo (Feb 20, 2014)

I have found that sprung trucks on model trains do not do much....the cars are too light weight to have any effect on the springs.....


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## gregc (Apr 25, 2015)

traction fan said:


> My question is, are frogs and wheels designed to let the wheel's flange bear some of the weight of equipment while a wheel's tread surface is not supported by rail; as when passing through the open area of the frog?


Tony Koester's articles on handlaying turnouts describes filling the flangeway of the frog with solder and using a hacksaw blade to cut the flange deep enough that the wheel flange actually rides on the solder. This, of course, prevents the wheel from dropping into the frog.

modern day frogs are not built from separate rails like most model turnouts. They are one piece, flanges are shallow and may be designed for the wheel flange to ride on them










flange bearing frogs are very different. they are designed to allow higher speeds on the main route and the wheels actually ride over the rail on the less used diverging route


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## 1905dave (Sep 18, 2016)

traction fan said:


> My question is, are frogs and wheels designed to let the wheel's flange bear some of the weight of equipment while a wheel's tread surface is not supported by rail; as when passing through the open area of the frog?


Short answer is yes and no.

The vast majority the answer is NO. The flangeways are narrow enough that the tread of the wheel maintains contact with either the rail or the guardrail entirely through the frog. The flange edge should never touch the bottom of the flangeway.

Having said that some trolley switches are deigned to support the flange and there are som specialized frogs that are used in very low speed applications where the flange does contact the flangeway and it actually lifts the diverging route wheel over the normal route rail.



> Commercial, model turnouts have flangeways that are deeper than most model wheel flanges. They let a wheel fall into the open area of the frog, and then be bounced back up when the wheel tread hits the frog's point.


What's really happening is that the flangeways are too wide and allow the wheels to drop in. If you added shims to the wing rails on the rubbing surface to narrow the flangeways to NMRA standard, the wheels would stop dropping in.


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## traction fan (Oct 5, 2014)

*Thanks, that's What I do too.*



gregc said:


> Tony Koester's articles on handlaying turnouts describes filling the flangeway of the frog with solder and using a hacksaw blade to cut the flange deep enough that the wheel flange actually rides on the solder. This, of course, prevents the wheel from dropping into the frog.
> 
> modern day frogs are not built from separate rails like most model turnouts. They are one piece, flanges are shallow and may be designed for the wheel flange to ride on them
> 
> ...


gregc;

Thanks for your informative response. When I make my N-scale turnouts I also fill the frogs with solder and cut flangeways into them. I use a razor saw; as a hacksaw blade might be too big for N-scale flangeways. The final shaping is done with a spare NMRA gage, drawing the flangeway tabs through to form a flangeway that is exactly the right size. This "carving" NMRA gauge" is not used for measuring, and the "measuring gage" is never used for carving. This is to prevent wear on a single gage, from carving, compromising its accuracy for measuring. 
Again Thanks;

Traction Fan:smilie_daumenpos:


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