Flange-ways in our Turnouts

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#41
It seems obvious to me that if flangeways are deeper than flanges, there will never be a problem. Use bottomless chasms, if you want. The RP-25 standard is designed to give you smooth movement through turnouts, but every part has to match. Change the wheel width, and you'll get better-looking wheels, but the price is likely to be a "dip" as the wheel passes over a frog. I've done a lot of hand-laid turnout construction, and our club uses some "semi-scale" wheels with the narrower tread width. I test every turnout with a car that has the narrower wheels, and I can make it run almost flawlessly, but it requires a little cheating: keep the flangeway adjacent to the frog to the bare minimum, and make it up on the opposite (guardrail to stock rail) side. What that does is to keep the most sensitive area, at the tip of the crossing vee, to the minimum width. There's no way to prevent that gap from having the width of two flangeways side by side, so it's best to keep them as small as possible. And geometrically, that keeps the area as short as possible too.

Of course, with a commercial turnout you'll have to live with the manufacturer's choice of dimensions. One thing you can do, if the flangeways are too wide, is to narrow them (not fill up the depth!) with a plastic shim. That should have the effect of keeping the passing wheels on the optimum path.
 

NP2626

Active Member
#42
It seems obvious to me that if flangeways are deeper than flanges, there will never be a problem. Use bottomless chasms, if you want. The RP-25 standard is designed to give you smooth movement through turnouts, but every part has to match.
I don't want bottomless Chasms! I'm unsure of what others might have problems with, as far as Flange-Ways are concerned. I'm saying that with ,025 deep flanges on our wheels, a .044 to .050 deep Flange-Way is too deep, when you consider that the wheels will not cross the frog without falling into the deep Flange-Ways of my turnouts.

In fact, using my NMRA Mark IV Standards Gauge, the only dimension I find lacking on on my Atlas Custom Line Turnouts, are the Flange-Way Depths. I should think being .020 to ,025 deeper than the Flange-Way gauge on the NMRA Standards Gauge would be an out-of-tolerance situation. However, with the deeper Flange-Ways, do my turnouts work? Yes!

This has been an interesting thread, I have been splitting hairs over the depth of the Flange-Way as I think the manufacturers could do a better job. Possibly the fix is to narrow-up the Flange-Ways to a more prototypical width. It's all the manufacturer's call.
 
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beiland

Active Member
#43
.....
I test every turnout with a car that has the narrower wheels, and I can make it run almost flawlessly, but it requires a little cheating: keep the flangeway adjacent to the frog to the bare minimum, and make it up on the opposite (guardrail to stock rail) side. What that does is to keep the most sensitive area, at the tip of the crossing vee, to the minimum width. There's no way to prevent that gap from having the width of two flangeways side by side, so it's best to keep them as small as possible. And geometrically, that keeps the area as short as possible too.
I have a couple of questions here. Those flangeways next to the frog are often termed the wing rails?

if you make them a snug fit while keeping the outer guard rails 'loose', don't you run the risk that the wheel will 'pick the frog' in the wrong direction?

I had been thinking that I needed a closer fitting of the outer guard rail,...combined with a somewhat rigid truck frame, to keep things running smoothly??
 

fcwilt

Active Member
#44
I have a couple of questions here. Those flangeways next to the frog are often termed the wing rails?

if you make them a snug fit while keeping the outer guard rails 'loose', don't you run the risk that the wheel will 'pick the frog' in the wrong direction?

I had been thinking that I needed a closer fitting of the outer guard rail,...combined with a somewhat rigid truck frame, to keep things running smoothly??
You want the flangeway on the outer rails to be a good fit so as to pull the other wheel away from the frog.

Ideally you want the depth of the flange way in the frog area such that the wheel there rides on the flange and doesn't drop down into the gaps. But if you have some wheels with deep flanges those wheels won't roll smoothly through the frog.

My Peco Code 83 Streamline turnouts have shallow flangeways in the frog area and a few older locos with deep flanges bump a bit as they go through.

Frederick
 

beiland

Active Member
#45
You want the flangeway on the outer rails to be a good fit so as to pull the other wheel away from the frog.
That's what I thought originally as well, but now we are hearing a different story.

Ideally you want the depth of the flange way in the frog area such that the wheel there rides on the flange and doesn't drop down into the gaps. But if you have some wheels with deep flanges those wheels won't roll smoothly through the frog.
That is not always true,.... needing those flanges on the wheels to be supported from the depths. If we tried to make those depths all exactly the same we might not be able to run a wide variety of trains. And since depth does not seem to be that great of a problem with derailments, I opt to have to have some tolerance to the depth of my flangeways.
 

fcwilt

Active Member
#46
That's what I thought originally as well, but now we are hearing a different story.


That is not always true,.... needing those flanges on the wheels to be supported from the depths. If we tried to make those depths all exactly the same we might not be able to run a wide variety of trains. And since depth does not seem to be that great of a problem with derailments, I opt to have to have some tolerance to the depth of my flangeways.
Which is why I said "ideally" and mentioned the problem with wheels having flanges that were deeper.

I have not had a problem with derailments because of the shallow Peco flangeways in the frog area, just the "bumping" of those cars and engines that have the deeper flanges.

Frederick
 

NP2626

Active Member
#47
I would challenge all of us to find wheel flanges deeper than .025. If it is on a locomotive, that's one thing, if on rolling stock, why wouldn't you change the wheels out for wheels with .025 flanges.
 

NP2626

Active Member
#48
I think we're getting close to the heart of what is my "Bone to Pick". That is "Tolerances". NMRA Standard S-3.2 describes the following measurements: Gauge at Frog, Check Gauge, Span, Flange-Way, Points and gives Tolerances for all five of those dimensions. However, when it describes the H dimension (The depth of the Flange-Way), it only gives .025 as a minimum for both HO and OO scale! Had I been working with whatever committee came up with S-3.2, I would have felt that there should be a maximum depth, .025 +.005.

NMRA S-3.3 (Deep Flanges) describes dimension H as .047 deep (this would seem to describe Atlas Custom Line Turnouts).

Certainly manufacturers can keep tighter tolerances than what HO standards currently use. For instance: I don't understand why the space between the point rail and stock rail are so wide; or, why the Flange-Ways are so big. However, these dimensions do work; so, other than the comment just made, I am good with how things are.

Again, I want a Code 110 wheel width, because of the slop built into track dimensions; but, like everyone else. I want my layout to look as real as I can get it. In the end, how important is any of this, anyway? It's in the "Eye of the beholder" Possibly, where I to start over in Sn3, I would hand lay and correct some of these things on my own, simply because I've "Thrown the gauntlet down" for myself!
 
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NP2626

Active Member
#49
I also believe that if we were to completely go "proto scale", we would introduce problems simply due to the fact that the size and weight of our models don't "Scale Out" to things which work in full scale.
 
#50
There's no spec for the flangeway max depth because the flanges should never reach that far! Hence "bottomless chasms"--make it as deep as you want, as long as it's deep enough. Should I not make cracks like that? (Ha ha)

Wheels shouldn't take the wrong route through a frog, regardless of whether the guard rail keeps the flanges away from the frog, even if they're set for minimum width adjacent to the frog. Set things up so the tolerances match RP-25, and it will work. The reason to keep the flangeway adjacent to the frog to minimum size is to make the gap between the two running rails in the "throat" region as small as possible, which also makes that area as short as possible along the length of the turnout. This has the effect of reducing that "dip" effect as wheels roll by. If you use narrow wheels which don't meet RP-25, it's the best result you can get. It can certainly be good enough to avoid derailments.

If anyone's interested, there's a Handlaid Track group on Yahoo Groups. It's hasn't been very active lately, but a discussion about basic track geometry should get some responses!
 

beiland

Active Member
#51
Define RP-25 Wheel Configuration

I see this 'incomplete' RP-25 subject come up again. Correct me if I am wrong, but aren't there at least 2 different RP25 wheels?
1) those with a tread width of .110 inches
2) and those with a tread width of .088 inches

Those 2 different wheels (both RP25's) can work different 'magic' in our turnouts. I think in our follow up discussions we should be using .....RP25-110, or RP25-88 or similar designations??
 

Sirfoldalot

Plucked Tailfeathers
Staff member
#52
You guys are doing great with the discussion - keep it up.
OK, being out of the hobby for many years, I have something I'd like to add and see if it has any merit?
Maybe the contour on the wheel tread should have a greater angle than RP25 provides?
Would this make a difference as far as keeping the car riding in the center of the track gauge? OR, does the RP25 provide enough contour?
 

fcwilt

Active Member
#53
I see this 'incomplete' RP-25 subject come up again. Correct me if I am wrong, but aren't there at least 2 different RP25 wheels?
1) those with a tread width of .110 inches
2) and those with a tread width of .088 inches
If you reference the RP-25 document it lists ten different sets of dimensions - two of which are the "code 110" set and the "code 88" set.

Frederick
 
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NP2626

Active Member
#54
Beiland, do you have access to the NMRA standards? I think they are available to everyone, not necessarily members. RP-25 describes the contours of our wheels, only. RP stands for Recommended Practice. The RP are simply recommendations. S=Standards. The Standards are stronger criteria that our trains are supposed to meet. It is in the best interest of all manufacturers to have their products meet all Standards as is it recommended that all manufacturers meet Recommended Practices. Nothing in model railroading must meet any Standards or Recommended Practices. There are no laws that pertain to model railroading that I am aware of.

Asked by Sirfoldsalot:
Maybe the contour on the wheel tread should have a greater angle than RP25 provides?
Would this make a difference as far as keeping the car riding in the center of the track gauge? OR, does the RP25 provide enough contour?


​I think that RP-25 does a good enough job.​



 
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#56
Code 88 was extensively used on HOn3 wheels.

The RP25 standards aren't set by scale, they are based on the "size" of the wheel. For example a prototype wheel is roughly between a code 72 and code 54 wheel (it would be about a code 63 wheel).
 

NP2626

Active Member
#58
Beiland, good idea posting RP-25 here, so we can all see what it says. dave1905 is correct, RP-25 describes wheels by their "N" dimension. I have no idea what scale a .175 wide wheel would work out to be. However, in the chart, we do know that .110 and .088 wheels mostly pertain to Standard HO. For more information you could look at S-4.1 Proto scale wheels, S-4.2 Standard Scale wheels; or, S-4.3 High Rail Scales. RP-25 really only describes wheel contour for the various sizes of "N" given.
 
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Selector

Active Member
#59
The various dimensions pertain to thousandths of an inch. Code 100 rail is 100 thousandths of an inch in height from the bottom of the flange to the highest point of the head's bearing surface. RP 25 gives, as the chart suggests in the first column, the N (for "nominal") width for the appropriate scale and tolerances based on probability functions. I don't know what they use, maybe a standard score conversion based on probability tables. You can't use, satisfactorily and practically, fine scale wheels in the very thin (but-oh-so-realistic) 054 range on a standard NMRA compliant Peco or Atlas because the wheels aren't wide enough to meet the frog point partway along their transit over the adjacent wing guards the same way Code 88 wheels will do on the equally NMRA compliant Fast Tracks turnouts.
 

NP2626

Active Member
#60
I got to thinking about what the "N" Dimension of a full sized Railroad wheel was. I googled: "What is the width of railroad wheels". This brought me to a place where many dimensions of wheels, axles and other RR stuff was displayed, however, the width of the wheels was difficult to determine. I found one drawing that stated 5.5 inches and another that said 6". In 1/87.1 scale, this works out to .063 wide and .068 wide, I guess you takes your choice. O.K., then this got me to thinking what does 4 feet, 8 and 1/2 inches scale out to in HO and this works out to a gauge of .6485. NMRA Standard S-3.2 states HO Gauged track is to be .651 +.010 and - .002. Then, I got to thinking: Well, what would O Scale split in half be (Half O, = HO). I discovered this was a bad way to think about it and abandoned the thought!

I knew that HO did not work out to exactly 4' 8.5 inches in 1/87.1 or .6485, because of some discrepancy that occurred back at the beginning of the development of the scale. However, now I felt I needed to go down to the layout and take around 20 gauge measurement with my Dial Calipers. I found all my track to be within tolerance and ranged from .650 to ,660.

To confuse myself even more, I looked into the low and high dimensions of Proto 87 and Fine Scale HO! Proto 87 does not have a nominal; but, lists .649 to .663 as the range for the Proto 87 track. Fine Scale HO (which I had heard of; but, thought meant Proto 87) also does not list a nominal gauge; but, a range from .649 to .665. Good luck with all this information!
 
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