Recently I saw a piece of equipment that I’d never seen before. It was a 65-70 ft. long tank car painted a light gray color and on each side it displayed two Union Pacific heralds. The words “Scale Monitor Car” appear stencilled on the car body.
Now I’ve seen U.P. and W.W.I.B. (Western Weighing & Inspection Bureau) “shorty” scale test cars, each equipped with two axles, four wheels, and no air brakes. I’ve also seen what appear to be around 40 to 50 ft., two-truck/four-axle scale test cars as well, but I’ve never seen a tank car in “Scale Monitor Car” service.
Que pasa? Does anybody have any idea as to the purpose of these cars?
Only a theory–but I suspect that using a car such as this gets around a lot of the speed restrictions imposed on more normal scale cars, due to their short length or other such factors. Keep in mind that those little 20-footers are all pretty old, and probably don’t have roller bearings.
I’ve also seen UP use some ex-MP covered gondolas as scale cars.
It may well be a scale test car, but scales aren’t that big…are they? A smaller car would be more of an obvious choice for the chore. However, the C&NW had a few big scale test cars, but they weren’t more than 45’ long.
I’m stumped…All of the other places on the net’ say that these are indeed scale test cars. Definatly the largest I’ve ever seen
Notice on one of the photos at Elmhurst, IL that there are more than one of these cars connected together…
I’ve seen as many as three of them at once, and know that at least four exist.
Longer cars shouldn’t make any difference, as weigh-in-motion scales weigh only one truck at a time. An older scale would have to have “live” rails as long as the longest car expected to be weighed there.
A typical scale has two sets of rails going over it, a short distance apart. The live rails are those that would give a reading on the scale; the others would not. It wouldn’t be necessary to separate the cars to move an adjacent car over the opposite set of rails. I hope someone has a picture of a track scale installation to better illustrate what I’m trying to say.
I think I can explain it better. At the scale there are four rails much like a gauntlet track. Two are on the scale and two are on the ground or support beams. The idea is you use the two rails on the scale when pushing a string to be weighed. then you throw the turnout points and bring the cars back on the nonscale rails so you don’t cause wear and damage to the scale. the rails are less than a foot apart in most cases. By the way (pun intended) scale cars do not have brakes so there is no loss of weight for brake shoe wear. If you look at those UP tanks they do not appear to have any brakes. just an airline to send air to the cars following. Many railroads towed their scale cars behind the caboose for that reason. I suspect that with the cost of metal a tank full of water is easier to adjust and has less value
Yes, the units pictured here are exactly like the ones I saw recently.
UP 903027 is equipped with air brakes.
I wonder if these cars, being of defined weight (plus or minus a few pounds due to air brake wear), are used more for calibrating the retarders used in hump yards rather than for calibrating track scales per se.
