# USAT F3 and back to back wheel gauge…



## Michael Glavin (Jan 2, 2009)

I have found the NMRA standards for wheel gauge, but was wondering if this is what works for those that have ventured down this path.

Since I have to re-gauge the wheels on several F3’s that have been fitted with the proto-typical correct height NWSL stainless wheels sets and replace the atypical USAT cracked axle gears I figured I’d inquire of those with more experience running trains and what works best in the real world…

Thanks for your help,
Michael


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## Greg Elmassian (Jan 3, 2008)

I use the NMRA standards, but not their idiotic tolerances. Use the target value. 

The wheel sets are nice, but never had problems with USAT loco wheels, because they are not steel underneath the plating (as opposed to Aristo for example). The USAT flanges are pretty deep, and since it is a 2 axle truck, it will tolerate smaller flanges. 

My target is a 2mm deep flange, which can run on reasonably good (perfect not required) trackwork. I've never seen the replacement gears from NWSL in the flesh. I use the "collar" method to repair/prevent cracked "axled" (It's really the plastic gear housing that cracks, the axles are metal). 

But when you start using standards, don't forget your switches! Many have bad gauge, poor guardrail flangewidth, and poor frog construction. 

I've got 10 F3's so I guess I qualify with enough experience, but many may say I am not of "the real world" ha ha! 

Regards, Greg


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## Curmudgeon (Jan 11, 2008)

1.575" back-to-back. 
Pull the wheels out until correct. 
HOWEVER: 
There is one style wheel from NWSL that has hugely thick flanges, and won't work that way, takes some playing to get them right. BTDT 

If you have the BIG wheels with minimal flanges, be prepared to spen 60% of your running time putting it back on the track. 
BTDT. 

The USA blocks are not equalized, and the twist of most railroad r-o-w's won't allow the flanges to stay put between the rails. 



Don't use a Kadee gauge, it's probably wrong, based upon some prior "proposal" that the nmra floated, unless they have "fixed" it to the LATEST nmra "standards". 
NWSL used to put a note in with their replacement wheels to the effect that nmra standard is 1,595" and we find they work best at 1.600". 
Another of those early "attempts" by aforementioned nmra to screw things up. 
Get a dial caliper, and set them with that. 
Useful tool. 
So, if it's a Kadee, check it with a dial caliper BEFORE you start setting things.


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## Michael Glavin (Jan 2, 2009)

Greg, 

Thanks for your thoughts... I’ll go with the target value... 

The NWSL wheel sets are a little taller to match the scale wheel diameter with about a 2mm flange. 

Greg, and yeah you qualify as the real-world IMO… 

I just counted I have nineteen F3 A-B's now; real world probably NOT as many have limited if any run time. I model SP, six are NIB un-painted waiting for the scarlet red/grey bloody nose scheme (some day I'll have the time). I'm in between permanent homesteads, so I have to run trains where I can. Noel Wilson is minutes from my current home so I play trains with Noel and locals at the Santa Fe & Butthead RR located in the infamous town Rio Linda, CA… 

Counting the F3’s alarmed me; I had not given it much thought previously. Slowly over time I acquired them with thoughts of having various paint schemes and such, as deals came my way I continued to gather things up and low and behold I now have more than I really could ever need. I’m going to have to count the rest of my engines now; it will likely be as alarming! 

Michael


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## Greg Elmassian (Jan 3, 2008)

They are nice locos. I especially like the redundant power pickup, although it can be damaged from a bad short (the internal wiper on the axles). 

Hmm... I'm going to have to drag my butt up there some time and party with you wild men! 

Greg


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## Michael Glavin (Jan 2, 2009)

Dave, 

Thanks for your input. With your knowledge I went I measured the NWSL porkers I have against a set of new USAT drivers, looks like the flange is as you note thicker than USAT’s, looks like about 0.028 thicker via my dial indicator. 

Would you suggest thinning the flanges? I did this on some Aristocraft Pacific drivers, but have yet to test that drive train (I reworked the entire Pacific drive, fitted bearings throughout, trued and narrowed the drivers to NMRA baseline and mounted the motor over the top and added a flywheel. 

Michael


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## Greg Elmassian (Jan 3, 2008)

What I would do is set the back to back spot on. Now check the gage of the wheels, and see if it is close enough to the target values. I would use the G1MRA standards, the NMRA ones are still an "imperfect clone" of them. 

If, with proper back to back, you cannot be in the "neighborhood" of the right gage, then thin the flanges. 

That is a big problem on the Aristo steamers, if you set back to back right at the target value, your wheel gage is too wide... but the drivers are cast of pot metal, so they cannot make thin flanges. (Or at least that's my best guess)... 

I just got a lathe, and all the Aristo steamers are going under the knife! ha ha! 

The standards have a target for flange thickness. 

Regards, Greg


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## Michael Glavin (Jan 2, 2009)

Greg, 

I'll see what I can come up with and report back... Good advice… 

The Pacific wheels turn nicely on a Sherline lathe with a sharp bit, I assigned an axle to each driver, indexed each driver to its respective axle halve and turned away. I most definitely profiled the drivers, i.e., tweaked the flanges, trued the driver to its axle, matched all diameters, worked on the fillet and faced the outside of all. The drivers look great; we’ll be testing this one soon, its Noel’s! 

Michael


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## East Broad Top (Dec 29, 2007)

I can't speak to the F-3 specifically, but I spent 2 years authoring the NMRA's "imperfect clone" standards as Greg refers to them, and cobbled together a fair number of wheelsets to check how they'd work in the "real world" through the process. 

If the flanges are particularly thick (greater than .090") then the G1MRA/NMRA target back-to-back (1.575") will definitely give you trouble in terms of gauge and/or check gauge. (Hence the "idiotic tolerances" of the NMRA's "imperfect clone." They were specifically designed to compensate for thick flanges.) You can slide that back-to-back spacing to around 1.560" with the thicker flanges to mitigate that. That'll save you the trouble of turning the flanges thinner if you don't have to. If they're _really_ thick (greater than .100"), then you'll want to take a little bit off of them, but between .075" and .090", you should be able to compensate by squeezing them a touch closer together. The back-to-back must be greater than the maximum span width (distance between outside edges of the switch guard rails), which is 1.555" maximum by G1MRA and NMRA. See Greg's note about checking your switches, though. Many switches are narrower still, and may still give you fuss. 

Later, 

K


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## Greg Elmassian (Jan 3, 2008)

I will state that the NMRA standards have improved... and Kevin, I believe you helped get them better. Don't take it negatively, it's better. It's just that sliding the back to back also wreaks havoc with what you have to do with switches, and by using such wide tolerances, now your switch frogs cannot support the wheels like they were designed to. 

This then forces you to have "flange bearing" frogs, to keep wheelsets from dropping into the frog just ahead of the points, because the throat is so wide because the wing rails now are miles away from the frog, i.e. cannot support the wheel tread. 

Of course, we can keep regressing back in time, and do what LGB did, huge flanges, 3mm tall, ALL cars and locos with the same flange depth now required and really wide wheel treads. 

All of that will work. Looks like crap but it will work. 

You just can't play with the back to back without it affecting something else. 

Greg


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## East Broad Top (Dec 29, 2007)

It's just that sliding the back to back also wreaks havoc with what you have to do with switches, and by using such wide tolerances, now your switch frogs cannot support the wheels like they were designed to. 


Not the case, though. The numbers on the chart are only half of the story. You've got to look at the footnotes in the standards. They explain how the tolerances are designed to be used to compensate for this, that, or the other. In the case of the back-to-back tolerance, they're specifically designed to compensate for thicker flanges. If you've got flanges that are on the thick end of the spectrum (potentially even exceeding specs), then you compensate for that by narrowing the back-to-back spacing. You're not using the narrow end of the back-to-back spacing with "normal" or even thin flanges. In terms of the frog supporting the wheel, you'd have the same amount of support on a wheelset with "normal" flanges and a b-t-b of 1.575" as you would on a wheelset with thick flanges and a b-t-b of 1.560". 

While we use back-to-back spacing as the paramount dimension in terms of measuring the gauge of our wheelsets, its success as a true measure is dependent on some level of consistency in terms of flange width. If they're all over the board, then your wheelsets will likewise be a bit unpredictable. That's why keeping the check gauge of the wheelset to a target is also important. Check gauge is the distance from the back of one wheel to the intersection of the flange and tread on the opposite wheel. (back-to-back plus flange width). On a switch, the check gauge is the distance from the outside edge of the outer guard rail to the point of the frog. So long as the wheel's check gauge is less than the switch's, there's no physical way for the wheel to pick the frog of the switch. You don't want the wheelset's check gauge to exceed the switches, and you don't want the wheelset's b-t-b to be less than the span of the switch. So long as you hit those two goals, you shouldn't have any troubles on the switches. 

In terms of the wheels riding on their treads on the frog rails as opposed to on their flanges, that's a function of a few attributes. First, there's the tread width. The wider the tread, the longer it's in contact with the wing rail as it diverges away at the point of the frog. The longer it stays in contact with that rail, the greater the possibility that the point of the frog will ride up underneath in the mean time, so the wheel never really drops off the rail through the opening in the frog. The next consideration is the width of the flangeway at the frog. The wider this measurement, the greater the distance from the wing rail to the tip of the frog, and the greater the potential for the wheel not being in contact with either the wing rail or the frog. Gauge is also a consideration here. The closer the gauge of your wheels to the gauge of the track, the further the wheelset will inherently keep the wheel over the frog as far to the wing rail as possible. The key is balancing all of these attributes for reliable operation over the frog. You don't want your wheels too wide, lest the check gauge of the wheel exceed that of the switch, at which point things go bump. Too narrow, and you run two risks - bumping up over the guard rails because your b-t-b is less than the span, or dropping the wheel into the frog because the outside edge of the wheel is closer than "ideal." 

BTW, in terms of wheel widths, G1MRA's wheel standard (.236") scales to 6.5" in 1:32. That's prototypical for standard gauge equipment at that scale. Since that's the only scale G1MRA is really concerned about, that's all they needed. The NMRA standards take all the various scales into account, so the wheel widths allow a range of .236" to .271", which scales to 5.5"--accurate for a narrow gauge wheel at 1:20.3 The width of the wheel only comes into play in two key areas. First, the switches as discussed above, and on the other end, the width of the wheel plus the check gauge has to be larger than than the gauge of the track, lest the wheel fall between the rails. Even at the minimums for b-t-b, flange width, and wheel width, this cannot happen under either G1MRA's or NMRA's standards. Most commercial models have widths in excess of G1MRA's standard already. 

Later, 

K


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## Greg Elmassian (Jan 3, 2008)

Kevin: 

Paragraph one... yes understand, on a level of how difficult that was to understand, it was about a 2 on a scale of 10... My previous posts should show I understood that... since you seem to be referring to me, please read what I write, not just the keywords in the sentence. 

Paragraph two... ummm..... also within my understanding "track", almost insulting... please stop telling me the obvious... I think I also have spelled out that I understand this tons of times, not just in this thread... 

Paragraph three... you are restating what I put in my post... why? again, re-explaining to me what I just posted above is pretty much a waste of time, at least for me... 

Paragraph four... I agree, the NMRA standard tries to "embrace" a wider variation in tread widths to accommodate a wider variation in the "desired" width, driven by the different scales in "G" or "Large Scale"... Yes a wider tread width is one way to handle what you outlined. 

Please do me the courtesy, if you are going to recount all the ways stuff works, it comes across as a lecture. Doing just after I make the same points comes across as condescending or insulting. It's not a competition. 

My previous post had a point, to try to indicate that if you start "sliding" in one direction, you will eventually come up with the "package solution" that LGB did, narrower BtoB, flange bearing frogs, wide wheel tread widths, sloppy flangeway widths. 

The way I took your post is that there was no point, just recanting the basic mechanics of how wheels and switches work, BUT it is juxtaposed with my post, and comes across as a REPLY. 

I appreciate what you have done in the group, but I was hoping to have a discussion, not a lecture on the basics. 

You may not have intended it this way, but that's the way it came off to me. 

Regards, Greg


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## Curmudgeon (Jan 11, 2008)

Hang on a minute while I go dig out my old trunk with the boxing gloves in it.


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## Michael Glavin (Jan 2, 2009)

Posted By Curmudgeon on 30 Sep 2010 10:01 PM 
Hang on a minute while I go dig out my old trunk with the boxing gloves in it. 

Will there be cigars???? 

Seriously I appreciate the info.

I'm going re-grear, set the back to back and give em a go at Noels place Sat AM for the LiveStream show, hopefully (been under the weather of late). 

Sounded like the “repair” i.e., with a custom axle-shaft collar was effected after the fact recycling the gears, is this the case? 

Michael


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## East Broad Top (Dec 29, 2007)

You may not have intended it this way, but that's the way it came off to me. 

Certainly not my intention. 

Later, 

K


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## Curmudgeon (Jan 11, 2008)

Looks like no stogies. 
However, POPCORN!


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## bnsfconductor (Jan 3, 2008)

I replaced my USA wheels with NWSL semi-scale wheels and gears a while ago and set them to 1.575" spacing like Dave suggested and haven't had a problem yet. But be sure to look out for the NWSL scale wheels (not enough flange). They might look great on the shelf, but they will derail on the railroad.


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## Nicholas Savatgy (Dec 17, 2008)

Posted By Curmudgeon on 30 Sep 2010 10:01 PM 
Hang on a minute while I go dig out my old trunk with the boxing gloves in it. 

Like you can still lift them !!!!!!!!!!!!!!!!!!!!!!!!!!


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