Intro
This is a simple jig for performing quality control checks on locomotives and cars. I built a similar one for my N-scale equipment (see article). That article also mentions the magazine article from where I got the original idea.

Construction
I started off with a 15" by 6" piece of MDF upon which the jig will be built. Any base material will do, as long as it stays flat over time. The length depends on the equipment to be checked. I will be running mostly 40-foot or so equipment, so mine is large enough to handle a 50-foot car or engine, just to be safe.



After measuring S-Helper Service's flanges, I realized that 0.040" is thick enough for the wheels to ride on. The point is that the bottom of the wheel flanges shouldn't ride on the base. I cut two one-inch strips of 0.040 styrene and glued them to the base using superglue. The height of the styrene verifies that the wheels all adhere to a minimum flange height. I glued the styrene pieces the same distance apart as my rails on the layout, so that wheel gauge can be checked quickly.



The next step was to deal with being able to install couplers on my cars and engines so that they all line up with each other. I settled on a scale 3-foot height from the tops of the rail to the vertical center of the coupler. People typically use the Kadee coupler height gauge for this check. That works fine, but what I really need to know is, do I need to adjust the truck/body height so that the coupler will wind up sitting at the correct height? The Kadee coupler height gauge also checks for that. But rather than spend $15, I decided to just make my own. Also, from my experience with the N-scale jig referenced above, it is a pain to only have one of those gauges on one side, because I had to always pick up the cars and engines and flip them around to check the other coupler. Now my investment would be $30. After some measuring I concluded that two pieces of 5/8" thick MDF cut to 1/4" width will tell me exactly whether or not the location of the coupler on the car or engine will be correct. The next photo shows one of those pieces glued down, centered in between the two strips of styrene.



This last photo shows the coupler on this boxcar is at the correct height. The top of this S-Helper Service coupler matches the top of the draft box, which matches the top of the MDF block.



Conclusion
It is a very simple jig that allows me to verify the correct location of the coupler, and to quickly verify that the wheels are in gauge and their flanges are of the correct height. Using a square, I can also check to see if the body leans on the trucks.