Wheel and Track Standards

[kstrong]

Preface
About two years ago, the NMRA put forth a proposal for large scale wheel and track standards. A copy of that proposal made its way into my inbox for me to look over. I read over what they had proposed, and found it quite out of line with what the large scale community had been doing. I drafted a letter to the NMRA expressing my concerns, going further to question the NMRA's involvement in large scale, given the perceived mutual exclusivity of the two communities. I was expecting a "thanks for your note" response at the most; more to the point, I was fully expecting to be completely ignored. Instead, the NMRA asked me to work with them, even to take a leadership role in the process. I could hardly justify turning them down, so I agreed to take on what had up to this point proven to be a very quixotic task.
 
The Process

Over the next year or so, I gathered information on what standards currently existed (G1MRA, MOROP), as well as measured wheels and track to see who was doing what, and how they compared to those standards. I talked to manufacturers and and others who have been involved in this process in years past to get their perspective. The goal was to come up with a set of standards tight enough to where trains would stay on the rails, but loose enough so that they allow for smooth operation of most of the models already being produced. Together with Gary Raymond, the NMRA's technical coordinator for large scale, and input from others in the large scale community along the way, we drew up three "levels" of standards for large scale, tailored to match the NMRA's standards format. Once we had our numbers put together, we took them to Didrik Voss and Ed McCamey, who head the NMRA's standards committee. (Forgive me if I'm getting the exact titles wrong.) Didrik and Ed took the numbers we came up with, and ran them through a series of mathematical equations that check for incompatibilities (i.e., wheels wider than track, etc.), and came back to us with their results. With just a little adjustment here and there (in most cases, no more than .002") we finally agreed on a set of numbers that should provide a solid foundation for large scale wheel and track.

 

The Proposal

The full proposal can be viewed here: http://www.nmra.org/standards/sandrp/pdf/LargeScalesv1-5.pdf 

 

What it does:

The proposal establishes a single wheel and track standard for all of the principle scales that run on gauge 1 (45mm) track. This includes scales from 1:32 to 1:20.3. The thought process there being that trains of all those scales are inherently designed to run on the same track, therefore a single standard regardless of scale would ensure maximum compatibility. The proposal does allow for a fair amount of flexibility in terms of tread width, flange width, and flange depth so that a manufacturer of 1:20.3 trains can develop a wheel profile suitable for that scale, while leaving the 1:32 manufacturer free to use a wheel profile with a more scale appearance for that particular scale and still be compliant. 

 

The proposal establishes two basic standards, a "standard" profile and a "hi-rail" profile. The only difference between those two standards is with regard to flange width and depth. The "hi-rail" standard allows for deeper and thicker flanges than the "standard" standard. Manufacturers are already building wheels that fall into the specs for both of these standards, and run successfully in the garden, so there's no worries about one being "too finescale" for outdoor use. There is no difference in track standards between the two sets of numbers.

 

The numbers in the proposal closely mirror certain G1MRA standards which have become common practice in large scale (such as a target back-to-back spacing of 1.575"), but tolerances have been loosened here and there to accommodate legacy products, such as older locomotives with much tighter back-to-back spacing or deeper wheel flanges. These legacy dimensions may exist outside the specifications, but the track standards are designed such that they should still operate smoothly.

 

What it does not do:

The proposal makes no attempt to individually identify any of the scales in the 1:32 to 1:20.3 range so far as wheels and track are concerned. Historically, the notion of individually identifying each of the various scales has never caught on, so the committee decided there was no point in doing something that was going to be completely ignored anyway. Instead,they are all grouped under the generic "LS" heading. One set of numbers, one overall classification. ("Fn3" is singled out in the Proto specifications, not covered by this proposal.) This proposal also does not directly specify standards for 7/8" scale (2' gauge on 45mm track) or 1:20.3 (F) Standard gauge (70.6mm gauge), though recommendations for those scales are mentioned in the footnotes.

 

This proposal also does not address anything above the wheels and track relative to large scale. It doesn't set coupler heights, interfaces, operational protocols, or anything of that nature. It is singularly aimed at the interface of the wheel and rail. 

 

My Editorial Comments

I expect the immediate reaction to this proposal by some members of the large scale community will be that it's viewed as an intrusion on large scale by a group that has "no business" messing around with us. Certainly previous attempts by the NMRA have resulted in numbers that clearly did not reflect the needs nor practices of the large scale community. I believe this time is different. The NMRA really changed their way of thinking relative to these standards. It was a bit of a tough row to hoe in the beginning, but our discussions over the past two years have opened a lot of eyes (mine included) as to how each community works. They really let go of a lot of control in this process. This proposal is in no way "them" telling "us" how to do things. These standards are fundamentally based on "our way of thinking," but presented in a format that meshes with the NMRA's standards format. Ultimately, the end result is the same--workable standards to which manufacturers current and future can refer when developing new products, ensuring our trains--past, present, and future have the best shot at staying on the rails. 

 

If you feel an uncontrollable urge to comment on this proposal, you may do so by clicking this link: http://www.nmra.org/standards/sandrp/consist.html then clicking on the "Comments from Members" link near the top of the page.

 

In Closing

I know there's a fair amount of anti-NMRA sentiment in large scale. In fact, it was my own biases against the NMRA that got me involved in the process. I would not have spent 2 years working on this if I felt it wasn't going to help the hobby. I don't care which letters are at the top of the sheet of paper, the concept of a set of numbers to which manufacturers can look to establish a baseline for their products will ultimately be a good thing for all of us. We've all spent too much time trouble-shooting switches and re-gauging wheels for us not to recognize the need for some sense of agreement. The manufacturers have been marching there--slowly--if only because we complain when things don't stay on the track. This proposal serves as a guide, reinforcing the direction that many of these manufacturers have gone, and hopefully providing a bit of incentive for others to join along. 

 

Later,

 

K

 

[cabbage]

QUOTE:

Together with Gary Raymond, the NMRA's technical coordinator for large scale, and input from others in the large scale community along the way, we drew up three "levels" of standards for large scale, tailored to match the NMRA's standards format. Once we had our numbers put together, we took them to Didrik Voss and Ed McCamey, who head the NMRA's standards committee. (Forgive me if I'm getting the exact titles wrong.) Didrik and Ed took the numbers we came up with, and ran them through a series of mathematical equations that check for incompatibilities (i.e., wheels wider than track, etc.), and came back to us with their results. 

UNQUOTE: 

Forgive my curiosity...

WHAT Equations did they use and WHERE did they source them from ?

Just a  simple question from an EU citizen and non NMRA member...

 

[cabbage]

 Since I have invited the NMRA via their representative to explain and document the validity and source of their formulae use for the generation of their tabled data. I think it meaningful and worthwhile to the discussion to examine the data tables and formulae that I have used to: design and built my own locomotives, and trackwork...

http://www.cabbagepatchrailway.co.uk/mls/HG/

The source volume is (of course), "Model Railways, Their Design, Details, and Practical Construction" by Henry Greenly Associate of the Institute of Locomotive Engineers. I have the 1924 Edition published by Messrs Cassel.

Note: this volume being over 75 years old is thus out of Copyright.

[kstrong]

Ralph, we took a more practical approach than theoretical in determining these standards. Unlike Mr. Greenly--who was most decidedly a pioneer in model engineering, we have decades worth of practical experience upon which to draw. We could look at individual wheelsets from various manufacturers to see what works and what does not. We also had to contend with established industry trends, which were likewise built on decades of history. For standards to be adopted, they have to play at least marginally well with what's already in the marketplace.

Besides, when you compare the NMRA proposal to the numbers Greenly writes about, they're remarkably similar in most areas. That should not be a surprise, since presumably G1MRA based their standards largely on Greenly's work, and these standards are based largely on G1MRA practice.

Later,

K

 

[ttrigg]

Kevin:  Looks to me as if you have been a busy lad! Large Scale is truly hard to define. Standardizing wheel sizes within each of the different scales of LS is going to increase reliability. Thanks to you for taking LS experience to the table for this discussion.

[Jerry Barnes]

 It's good you are doing this, if they will just follow them, in the future we might have one less problem anyway.

[Lee 1234]

You need to involve the manufacturers as much as possible. Remember they are the one's that make the equipment. If they don't buy in to what you propose then you have and will be wasting your time. Good luck on your endeavor.

[hudrail]

Hi I have been involved in the railway hobby full size down to 3.5mm for50 years . The very basis of railways and indeed all engineering production is standards . The industrial revolution was started by people like Whitworth who brought in standards , infact war was the first user of standards with cannon ball sizes bullet sizes etc . Having spent 40 years in model engineering when , due to ill health , I started G Scale , I searched in vain for a set of standards , none !  Some trains derail on others switches half the buckeyes wont fit the other halfs ! What a total mess ! Thank you for starting the Standards process every G scaler will in time come to thank you , even if they are at first unable to initally accept them . We should then complain about the suppliers in these pages if they dont conform . Couplings or buckeyes should fit each other . I have spoken to two of the largest manufactures one said the dies are too expensive to change . Total rubbish select the best design then share the dies for those ones . Larger order , so savings there , two companies to pay for new dies when they ware out . Every body wins . Thanks to all the people who started the process ignore the flat Earth brigade