Use of the NMRA Gage

Model Railroader General Discussion (Model Railroader)
1

I recently purchased a used Details West freight car and as with all my rolling stock I checked the wheels to see if they are in gage the coupler height weight etc. and of course swap out the wheel sets for metal ones. Being the typical insomniac model railroader Iwas watching some of the How to video’s on the site and recalled Jim Hediger showing the proper use of the NMRA gage and all of it’s features etc. Here is where my quandary begins. Jim explained about the use of the no-go gage for checking wheel width. The original plastic wheels dropped right into the slot and had a little side play indicating the wheels are too narrow, so now I test one of the metal wheel and it doesn’t fit. Which is what it is supposed to do. So my question: is there a maximum wheel width or is it just an aesthetic thing?

2

Last time I was on the NMRA site (yesterday) I saw a table of wheel widths. HO is Code 110 (as usual, code 110 refers to “thousandths” of an inch). I’d link you if I knew how, but it’s in the “Standards and Practices” section of the site.You’re right of course, that the function of a “No-Go” gauge is to show if a wheel is too small. Sounds like you’re ok with the metal wheels, but skinny wheels would tend to drop down in the rail cutouts of a turnout and cause derailments. Hope this helps.

Lou

3

I don’t know anything about the “No Go”(never used it) since all of my wheels are RP25s I don’t worry about such things and I enjoy 99% derailment free operations-go figure.

4

In HO, the standard tire width is .110". That said, several manufacturers also sell .088" width wheel sets that ‘look’ better. Operation through the frogs on your turnouts might display some wooble…

Here is the NMRA page for the wheel standards:

http://www.nmra.org/standards/sandrp/pdf/S-4.2%202009.07.pdf

Jim Bernier

5

With 0,088’’ wheels you can build turnouts more prototypical, with smaller flangeways. But you have to adjust the gauge from your wheels, the distance wheel-wheel.

Wolfgang

6

Jim, and others thanks for the reply after posting I did go to the NMRA website and couldn’t believe how much information there was just pertaining to wheels. Now I know what a friend meant when he told me he was slow switching out his wheels for one’s more prototypical. So I guess it comes down to a trade off of what looks better/more real for what runs smoothly

7

We have at FREMO a group who operates with this RP3/ RP4 standard. All turnouts are built according to a wider wheel flange-wheel flange distance. We have also a group who operates following 1:87 ! With those tiny wheel flanges! And it works with modules. And it looks good.

Wolfgang

8

If you want to learn all about the NMRA wheel, flange, and turnout standards, watch Tim Warris’s video series on the Fast Tracks web site: http://www.handlaidtrack.com/videos.php. It’s the series titled “Demystifying the NMRA Standards” He uses color-coded 3D CAD animations to show what the various terms mean, and how all the measurements interact with each other. Quite useful.

–Randy