How come NMRA HO fine wheels work on NMRA HO standard track?

I think you've found the/a hole in the NMRA standard.

Does this mean we get a rebate on dues ?

( sarcasm OFF )

Has anyone ever taken this up with the NMRA committee(s)? Should we? Did they have any comment?

They already know.

The relationship between wheels and rails is complex and there is not a defined relationship between all relevant parts that can be applied. When you alter one relationship all the others need to be adjusted as well within certain tolerances. Standard HO track has large (relatively) tolerances and the wheelsets are designed to work within those tolerances. IMHO the NMRA committee attempted with the RP88 wheelsets to design a wheel profile that would not drop into the older standard frog flangeways, hence the wheelwidth that is fractionally greater than the maximum frog flangeway width.

Narrowing the frog flangeway results in a shorter rail gap, which is the worst feature of NMRA standard turnouts. (wheel-drop) In setting a finer standard for this part of the wheelset/track equation the RP110 standard wheelset comes into conflict with the track standards at the extremes of wheelset standard tolerances.

If you want your RP110 wheels to run on the finer RP88 trackwork you need to refine the tolerances of the RP110 wheelsets.

Regards, Greg.P.

Go to the NMRA standards. You'll see that most of them have a recent date and "released for comment" notation. They've been changed to plug the hole.

IMO, a single standard that accommodates both code 110 and code 88 wheels where it counts: turnouts.

It already exists and can be found on my web site. Known as 00-SF in the UK, (I expect my H0 version will be included in the Australian Model Railway Associations new fine tolerance wheel and track standard 2008). A company called Railway Engineering produces track and roller gauges close to these standards, as did a member on the 00- SF Yahoo group. These options all work perfectly with RP25-110 wheels that work on RTR coarse track. The NMRA fine scale standard uses a different check gauge compared to the RP25-88 style wheels you get from H0 suppliers, so ignore the NMRA H0 finescale standard if you want compatability with RTR.

Terry Flynn

HO wagon weight and locomotive tractive effort estimates

DC control circuit diagrams

HO scale track and wheel standards

Any scale track standard and wheel spread sheet

1) What are RP88 wheelsets? I assume you are referring to 0.088" wide treads? 2) And what NMRA commitee is in charge of that?

nmra.org

That's it! RP25/88 on a data sheet I have from somewhere long ago.

I'm not a member of the NMRA, it being from my point of view a foreign organisation.

A little research on the NMRA web site give this information for starters

Standards and Conformance Department Manager: Didrik A. Voss 15226 12th Dr SE Mill Creek, WA 98012-3082 O: 425-337-5222 F: 425-337-6084 E-mail: snipped-for-privacy@hq.nmra.org

The committee members under him can be reached as follows

The Standards & Conformance Department

• tech-chair@ The Standards & Conformance Department Chair * tech-dpty@ Deputy Chairs

• tech-mech@ Mechanical Standards * tech-small@ Small Scale Standards (TT, N & Z scales) * tech-mid@ Mid Scale Standards (O, S, OO, & HO scales) * tech-large@ Large Scale Standards (All scales larger than O) * tech-spec@ Special Standards (Proto Scale, Module Conformance & Traction)

• tech-elmgr@ DCC Electrical Manager * tech-elec@ DCC Electrical Issues * tech-dcc@ DCC Manager * tech-softw@ DCC Software

• tech-morop@ MOROP Coordination

• tech-stdrs@ Standards and Recommended Practices on the web

• tech-irg@ Issues Review Group

• tech-candi@ Conformance and Inspection Manager * tech-candi-com@ C&I DCC Command Station Inspection * tech-candi-dec@ C&I DCC Decoder Inspection * tech-candi-web@ C&I Web Pages * tech-candi-mech@ C&I Mechanical Inspectors

Don't forget to add hq.nmra.org after the @ sign.

Next time you might want to do a little research on the web your self.

Howard Garner NMRA Life 1425

THAT IS NOT AN NMRA COMMITEE.

Howard, I did.

The previous post referred to "...the NMRA committee..." with no clarification *whatsoever* of what comittee Greg Procter was referring to. news: snipped-for-privacy@ihug.co.nz

True, true, Marky.

Now go, and do your own research.

The "problem" is with finer scale track dimensions that are practical with RP25/88 wheels clashing with the RP25/110 wheelsets.

The reason I have some practical experience (stop reasding here) is that I model European prototype and scratchbuild a proportion of my stock. I have propriety rolling stock from as far back as fifty years ago, and need to have it operate alongside hand-built models. As I'm into early steam era I like finer scale wheels. As you can probably guess, the wheels were never intended to operate together and I'm never going to alter all my stock to one standard. I redo the coarsest loco wheels, upgrade wagon and carriage wheelsets and then build rebuild pointwork to match. I've been working through this process for 30 years but of course with each new loco there's the urge to use finer wheel standards and of course the proprietry manufacturers are slowly slowly doing the same thing.

My stumbling point is always the frog gap. Check rails can be shimmed to pull flanges away from the frog, but with the mix of standards the gap at the frog has to remain large. Proprietry manufacturers trying to retain backward compatibility have exactly the same problem. The two results are:

- the frog point/rail to check has to be wide to allow older standard wheelsets to pass outside the two opposing check rails. (the stock rail-check rail gap is small to pull the finer wheels away from the frog)

- the frog gap becomes unneccessarily wide to accomodate the above, resulting in a minimum tread width to avoid wheels dropping between the frog-check gap. Importantly, the large frog gap results in wheels dropping as they cross the frog gap.

Home built turnouts can be built finer than proprietry turnouts by reducing manufacturing tolerances, but that results in more maintainance.

Greg.P.

NMRA S-4.2 Wheels, Standard Scale was approved July 2004. NMRA S-4.1 Wheels, Proto & Fine Scales was appoved January 2006. NMRA S-3.2 Standard Scale Trackwork was approved July 2004.

This question was raised on September 21, 2007.

Thay *have not* been changed since Pekka Siiskonen raised the question.

2004 and 2006 _are_ recent dates.

The fact is that Siiskonen's question s raised some time ago, and from within the NMRA BTW. The NMRA is responding as best it can. Keep in mind that apart from some paid administrative help at the head office in Chattanooga, the NMRA is an entirely volunteer organisation. I wish people who bitched about its work would join and offer to help on the relevant committee(s) instead.

For the record: when I lived closer to the crowded parts of this continent, I edited a Divisional newsletter. Right now, I am a member of a Division that takes about two days to drive across from end to end. That limits my direct involvement, unfortunately.

HTH

Blow it out you arse, Mikey. You can't even read, or else you deliberately obfuscate. That is, you lie by telkling partial truths.

Copied from the Standards contents page on nmra.org. Note that "Upadted July 2007 - Released for comment".

STANDARDS Standards Gauge S-1 General Overview - PDF S-1.1 General Proto Scales - PDF S-1.1 - Updated July 2007- Released for Comment S-1.2 General Standard Scales - PDF S-1.2 - Updated July 2007 - Released for Comment S-1.3 General Hi-Rail Scales - PDF S-1.3 - Updated July 2007 - Released for Comment S-2 Couplers - PDF S-3.1 Trackwork Proto Scales - PDF -- Tech Note TN-1.1.2, Proto: Scale and Fine Scale revisions,

11/22/05 - PDF S-3.2 Trackwork Standard Scales - PDF S-3.2 Updated July 2007- PDF - Released for Comment S-3.3 Trackwork Hi-Rail Scales - PDF S-3.3 Updated July 2007- PDF - Released for Comment S-4.1 Wheels Proto Scales - PDF -- Tech Note TN-1.1.2, Proto: Scale and Fine Scale revisions, 11/22/05 - PDF S-4.2 Wheels Standard Scales - PDF S-4.2 Updated July 2007- PDF - Released for Comment S-4.3 Wheels Hi-Rail Scales - PDF S-4.3 Updated July 2007- PDF - Released for Comment