Wayne Roderick, 3rd Division, PNR, NMRA (life)

06/06/00 rev 01/16/07

The Teton Short Line has long welcomed visitors and encouraged them to bring their own rolling stock to play trains with. Part of this effort is to teach the techniques of good track/wheel relationship. A very good tool for this purpose is a device the quickly checks for the most common wheel and coupler problems that are not immediately obvious by quick physical inspection. We have an inspector stationed at trackside to check the wheel guage and look for low hanging air hoses commonly used for uncoupling Kadee couplers. For safety reasons we can't let this fellow crawl under cars so the TSL Engineering Department built him an automated device. It has worked so well that we built one for the local Pocatello Model Railroad and Historical Society where it was needed even more because hundreds of privately owned cars operate on the club trackage.

Click on the thumbnail for a VGA (640x480)
Overhead view of the wheel guage inpector on the PMRHS and Teton

Refer to the NMRA standards S2, S3s and S4 for track & wheel relationships. The "WHEEL CHECK GAGE is the distance from the Back of the flange of one wheel to the tread side of the flange of the other wheel of a wheel set"

If you don't have the NMRA Standards guage, don't waste time reading further until you go buy one! The easiest way to build and set up this device accurately is to use a truck that has been very carefully adjusted to the Standards guage. That's the truck with the yellow paint on it in the photo. This avoids 'rithmetic and fussing with tolerances.

Each stock rail is equipped with a guard rail that is positioned at the minimum flangway width of .050 (1.27mm) for HO. One of the rails is sectioned and hinged so it is able to move to accomodate the wheel set as it squeezes through. The unmovable flangeway should be fairly long while the movable flangeway should be short and built with a curved guard rail. Now all we have to do is figure out how to build it and measure the flangeway movement.

For accuracy and stability I chose to use a piece of printed circuit board, available at Radio Shack, for the substrate. Everything is soldered firmly together and electrical paths are milled with your Dremel tool. Music wire forms the shafts and springs, while K&S tubing forms the bearings. The very small movement of the flangeway must be multiplied with leverage (mine is about 20/1) to make contacts in the inspectors shanty. as shown with his shanty removed. The pix tells the rest.

Click on the thumbnail for a VGA (640x480)
inside view of the inpectors shanty The red lamp projects through the roof and is track powered. The horizontal "propane tank" for warming the shanty is a resistor to limit the lamp current. The white plastic sheet is slipped under the moveable flangeway and dusted with graphite or teflon powder to make a slick bearing surface. The movable flangeway is made from lighter rail to make room for the .005 brass sheet under the flangeway and .010 plastic underneath it. Use code 70 for 83 or code 83 for 100 or simply file some of the base away before you assemble it. The long thin wire is a centering spring so that things are lined up when the wheelset approachs. No problem having this on the mailline, just make sure its got a few inchs of tangent track on both ends.

Set it loose to start with, and as you fix the worst violators, tighten up the tolerances and watch the derailment problems subside. You will be surprised how many pieces of rolling stock including engines are in bad guage right out of the box. How bad is bad. If they don't drop perfectly into the NMRA guage, fix 'em! Wheel guage is only one of the many items that contribute to zero derailment operations but others have spoken and printed many words, so we won't repeat it here.

In the intro I mentioned checking for low hanging Kadee air hoses. Sorry, but this newer one used on the PMRHS club layout that was unsceniced and easy to remove for photographing doesn't have that feature like the one on the TSL. Use your imagination and provide a vane between the rails that projects flush with the railtop and link it to some contacts in much the same way as we do for wheel guage. It really wouldn't help much to use a photo of the TSL version as that stuff is down in a hole between the rails and all you can see is a 1/4" wide vane projecting up 1/10 inch. I used an old set of long relay spring contacts to do the job.

Let me know if you find this useful.

Return to Teton Short Line Home Page