You quote a target wheel check gauge of 1.633”
The wheel check gauge, which we will call C and hold to be constant comprises of BTB or ‘B’ plus nominal flange thickness which we will call ‘A’.
IF we hold that C is constant then 1.633 ought to equal 0.074 plus 1.575. It does not – A plus B equals 1.649”.

Sam, this is closely related to Greg's post about b-t-b being his primary element. We could have easily changed the target b-t-b on the hi-rail standards such that C = the stated targets for A + B. But that would have muddied the waters because now we're sporting two separate back-to-back measurements. It's a case of "we know what the NMRA wants, but we also know what the large scale community uses." So, we kept the b-t-b the same across both levels of standards, confident that even if you were to use flanges at the upper end of the thickness spectrum, they'd still play very well with the track.

I appreciate that you have allowed 10 thou max + tolerance that would alleviate the issue but you cannot control whether the track manufacturer has erred towards the –ve tolerance, or the + ve.

It's the job of the manufacturer to make sure his manufacturing tolerances still fall within the scope of the standards. If the manufacturer's tolerance is ±.005, then he shouldn't be setting targets at the far edges of the range. While I appreciate there are instances where the manufacturing tolerances may be greater than the specified range, common sense would dictate you pick a value that gives you the most likely chance at conformance with the standard.

that is dangerous ground and allows playing fast and loose, which is the problem that we have currently.

What we have today is the result of 40 years of blatant disregard for G1MRA's standards, not merely playing fast and loose with them. That we've been generally successful in running such a random mishmash of wheels on such a random mishmash of track defies logic. I suppose if we weren't, we'd have tighter adherence to standards already, and this entire debate would be moot.

No good will come of having variations within a standard or providing standards tables where the figures do not add up unless you take the margins for error into account.

We'll have to disagree. I think when you take the standards along with the notes, the standards make a great deal of sense and--if adopted by the manufacturing community (and that's the $64,000 "if")--will have a very positive impact on the hobby and the ability to run socially without worry. It is going to be up to us to provide them feedback (both positive and negative) as to how they're doing relative to sticking to the standards. If they're misinterpreting something, we need to be proactive in correcting them. If they're hitting the nail on the head, we need to be praising them for it.

Later,

K

Kevin, I'm not impugning Gary's or your experience.

You said you did not understand why I said something, and I told you it was because YOUR top consideration is not MY top consideration.

Now, you should understand that and appreciate it and respect it. Maybe we don't agree on the top consideration, but respect should be given both ways. I'm respecting your decision.

I understand the politics you have to play in the NMRA... it is not really rocket science, and I am definitely smart enough to understand.

Don't fall into the trap of continually explaining the same thing because people don't agree, I understand, I don't agree.

Some of the people in the world can be overcome by just beating them senseless over and over with the same words... I am not one of them.

Regards, Greg

It's called "tolerance stackup", Kevin, where parts are at the extremes of the spec scale and they don't work.

I am using virtually all Llagas turnouts, some so old they have wood ties.
The "standard" in use, some extrapolated 15 years ago from G1MRA is:

1.777" gauge
1.574" back-to-back.
1.530" wing to guard.
You calculate the flangeway from that.

It has functioned flawlessly for all this time.

I have old LGB 1600's in the shed, and if you want problems, that's where they will be.

I know what works and can prove it.

nmra going to break tradition and actually BUILD wheel, track and turnouts to those standards and place them in real-time service to "prove" the concept?

Please pass along my message to the nmra to butt out.

If the (mainline) manufacturers of wheels cannot build to existing standards, even when it was continually pointed out to them, the last thing we need is ONE manufacturer coming out with something "different".

I am really sorry your turnouts and wheels don't work.

Maybe if you used turnouts that were to the existing standard, you wouldn't have this issue?

Back to logged-out status.

Thirteen freaking pages (on my settings).

Geez.

One thing is clear. There are as many approaches to developing standards as there are standards themselves. I think overall, each of our approaches and specific numbers are in reality quite compatible with each other, going back to Greenley's work which Ralph referenced some umpteen pages ago. "What works" for Greenley is specifically different from "what works" for Dave, which is different from "what works" for Sam, "what works" for Greg, "what works" for me, etc. Yet, all of us swear by what we're using, and have no trouble with it on our respective railroads. Each of our personal standards vary by just that little bit here and there. If nothing else, that would seem to illustrate that quibbling over a few thousandths of an inch is neither productive nor really necessary in the grand scheme of things.

I think we can all set our back-to-back wheel spacing to 1.575" (or 1.574") and be confident that we won't have trouble running on track built to G1MRA/NMRA standards. I don't think Dave's been turning his flanges down over the years, I know I never have. Greg would be able to buy a new locomotive with the scrap value of his metal shavings if he were. If (generally speaking) we're having success running the wheels we have now set to that spacing, and we know fully-compliant G1MRA wheels set to that spacing will work, then it stands to reason that wheels set to that spacing whose flange standards fall between those two points should have a similar success rate. Time will tell.

Later,

K

One final point. An acquaintance of mine was a professional design engineer on our rail network dealing with, among other things, the interaction between wheels and track in traction trucks. He assures me that the point of a guard (ckeck rail) is to prevent any contact between flange and frog with the exception of the root radius. Any hammer blow at this point is highly undesirable. While physics says that the coning etc should do this job in practice other factors apply to negate this at times. Hence the provision of guard rails as a preventative. As I said earlier they are not needed all the time, however when they are neaded in a given situation they do a valuable job. When the wheel/track check gauge relationship fails to do this job this accounts for that irritating intermittent derailment at a switch that is so difficult to diagnose. This can manifest itself as a % of locomotives/stock not derailing but other stock persistently derailing, or ones stock occasionally derailing because circumstances are such that the flange CAN strike the frog rather than be kept away from it by the guard rail.

The btb is important as a component of the wheel check gauge and its relationship with the span dimension.

A story as to why totally compatible standards without variance are important. On the Leighton Buzzard Lifht Railway (preserved industrial line) a visiting full size 2 ft steam loco became stuck fast in the middle of a grade crossing and three locos sent to pull it off could not shift it. In the end it took a 4X4. I know this because I was there at the time. On investigation it was fiound that the visiting loco had slightly different wheel set values from thos locos of the home fleet. While it coped well with the switches and most of the grade crossings the span of this particular crossing was a tad larger than the rest. The home fleet passed over this grade crossing OK but the variation of the visiting loco was just enough to jam it pretty tightly.

Sam E