How do they work? Because we have seen them on trains.
What kind of infromation do they collect?
A scale test car is just a calibrated weight. You center the test car on the scale and weigh it. Your scale should match the calibration value or else you fix the scale.
dd
They are used to calibrate car scales.
Because they are a fixed weight that never changes, you can use them to check what your scale states against what you know the car weighs.
No modifications or repairs may be made to these cars unless authorized by the railroad that owns them, so the weight of the car is not changed.
They are often filled with sand, or water, (sand is more common).
Most have no train brakes, only a simple hand brake, so the wear on the brakes doesn’t affect the weight of the car.
As the brake wear, they would get lighter, and alter the overall weight of the car.
You should only carry these cars on the rear of a train, due to their small size and fixed wheel set, and the fact they have no brakes.
They collect no information at all.
In essence, you are taking a known “standard” weight, and placing it on your scales, then compairing the reading from your scales to what you know the car’s weight is.
Ed
Ed,
Essentially correct, but one minor error. The cars weren’t loaded with sand or water. Most were riveted steel construction with access doors for placing NBS standard 50 pound weights. Some of the later designs were actually a one piece cast body, carefully cored to weigh 66,000 pounds plus or minus 500. Both designs had vertical ends and sloped tops to prevent rain and snow accumulation which would add weight. After construction was completed, the car would be weighed on a standard NBS scale and marked with the certified weight and date. They would periodically need to be recalibrated, but I’m not sure of the interval.
Scale test cars of the classic four-wheel design last almost forever since there isn’t too much on them that actually wears out. TRAINS ran a picture of one in the early 1980’s in the “Would You Believe It?” department which had attained its 90th birthday.
See, you learn something new here every day!
The two we have running around down here are filled with sand…don’t have the reporting marks, one is a ancient MoPac, from the 30’s, the other is a CNW…I know it is filled with sand, it got whacked and sideswiped by the crew who delivered it to us last year, and the round side door was ripped off…
Got nosey and looked in there.
Their TM had to come out and OK our rip guys repairing the door to the point it could be moved back to their shop for permanent repair.
But having the system Tom describes where you could add a known or standard weight would be so much easier.
Are they that accurate that a few pounds of brake pad would make a differance?
What is the resolution of the scales?
The read out in our scale house reads down to the pound…now, I am not too sure if it is truly that accurate or not, but I have sat there and watched the read out and checked it to a list our yardmaster had, they all matched.
If I weight some this weekend, I will ask what it is calibrated to…
Ed
i was wondering that to now i know.
In the NBS (now NTIS) system, there are both primary standards and secondary standards. The design with NBS 50 lb weights sounds to me like a primary standard, and knowing the NTIS from other experience, I expect that the primary standard cars are weighted to a tenth of a pound or better accuracy – thus the concern about brake pad wear.
A sand filled car sounds like a secondary standard. It is compared against the weight shown by a scale that has also correctly weighed the primary standard. Keeping the sand dry is important because it can easily absorb sufficient water to change the weight of the car by a few pounds.
The plus or minus 500 pounds on the cast type car is not the allowable weight error. The just want a very typical weight for the test weight. Each individual car would be weighted to at least a one pound accuracy to establish its calibrated weight.
It has always surprised me the a car so small can weigh so much.
dd
The one you’re describing sounds like one of the cast body ones. If you have the July 2005 Railroad Model Craftsman, look on page 70 for a picture. The door you’re describing is the tool compartment for the scale adjustment tools, and they have to be removed before the car is placed on the scale. There shouldn’t be sand in there. After any damage and repairs, the car will need to be recertified if it’s being used to calibrate scales. The date and place the scale test car was certified should be displayed, usually on a plate on the handrails. IIR
Little typo there dd, it’s NIST, National Institute of Standards and Technology, formerly NBS, National Bureau of Standards.
While we are on the subject…when do they use scales? Not every car is weighed. Remember the SP Cajon runnaway caused by a weight miscalculation.
Scales are used very often, espically with variable density loadings such as soy(having to do with it absorbing moisture, and gaining weight-also shortening its"shelf life" or, worse, contaminating it)Corn (which settles over time, so depending on when one loads it into a rail car, the car could appear “full” and not be near the stenciled weight of the car) or plastic pellets (one of the biggest pains in the [censored]if there is an air pocket inside the car) Coke is on this list as its weight:density ratio can vary widely, depending on how much of the coal’s weight, as mined, is burned off during the coking process. Then there’s the matter of settling disputed weights, between the two parties involved.
how common are weigh in motion scales? The only scales I have looked at up close don’t look like they can do this.
csx has one in C&O chessie paint.when it went over a crossing the train was accelerating out of town.i thought it was about ready for take off.
stay safe
Joe
We weigh loads and empties every day, once on the morning shift and once on the night trick.
Weigh the loads to make sure the are within the load limits, and the empties because there really is no such thing as an empty car, tanks especially.
There is always a residue left.
The idea, of course, is to know what the car weighed “empty”, the compare that to the same car loaded, so that…
A: The customer knows he is getting billed the correct amount on shipping.
B: The industry loading the cars knows it true start weight, so they know how much more they can load into it before they over load.(full donst always mean to the top of the car!)
C: Train make up and power requirements, (see the posting above about the SP goof)
D: Our on line customers need to know if they got what they were billed for…say they unloaded X number of gallons at so many lbs per gallon…compare that to what they were billed against what the car weighs “empty”, any difference and someone got over billed or short changed.
We use running, or weigh in motion scales, max speed over the scales is 4 mph…no locomotive is allowed to be stopped on the scales, but they can pass over it.
At $500.00 per car charge, and we weigh 20 to 30 cars a pop…well, for the amount of work involved it pays quite well!
Ed
Ed
$500 to weigh a car?!?!
When Proviso had a scale, I committed a major sin–stood on the live rail and had somebody print the ticket.
Yes, the scale was accurate!
http://www.ptra.com/pages/Supplement%201%20PTRA200A.pdf
http://www.ptra.com/pages/basetariff2000B.pdf
go to section 400, page 13 here…I was wrong, it is $400.00 per car…
You might read the whole tariff, it might surprise you what we do, and do not charge for.
Most railroads charge close to the same thing.
Ed