Freight Car Friday – Scale Test Cars

13 01 2012

It is fitting that we take a look at these special cars today, since it marks the 155th anniversary Thaddeus Fairbanks’ patent for the first track scale. These scales weigh an entire freight car, and its contents. Their primary use is for billing customers whose loads are paid for by tonnage. Scales are also used to weigh light cars when new, and periodically thereafter. This light weight helps determine the cars capacity and can be subtracted from total car weight when loaded to determine the billable weight. Some scales are owned by the railroad, others by the industries themselves.

Scale Test car

This small test car, still serving Norfolk Southern, weighs 80,000 pounds. Without a caboose, the car is placed between the last two freight cars of the train.

When money is changing hands, you know the scales have to be accurate. Neither side wants to be short changed or over charged. Railroads employ special test cars to calibrate these scales. These cars themselves are calibrated on a master scale, owned by the railroad and then sent around the entire system on a regular basis along with an inspector.

Historically, most scale cars have been home-built. Earlier cars were quite short, on account of scales which had small segments needing individual calibration. No matter their size, all scale cars are carefully weighted and maintained.

scale house

This scale house, now closed, is a typical design and featured a gauntlet track for the scale. The weighing track (since removed) sat just to the left of the running rails still in place. This provided a bypass for locomotives or when not weighing cars.

Alterations to the cars, even changing a broken coupler, can only be done with the permission of the scale inspector. For this reason, many early cars lacked air brakes – the gradual wear of the brake shoes would offset the balance. Such cars could only be handled at the rear of a train, immediately ahead of the caboose.

These small test weight cars normally enjoyed very long lives. Some served nearly 100  years before retirement. Many can be found at museums today. Conventional freight cars were also converted for use as test cars. Filled with concrete or scrap steel and sealed, these cars never left a railroad’s home rails so age and interchange rules were not a problem.

With their distinctive shapes, exceptional lifespans and interesting operations, a scale car is an interesting addition to any freight train.

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One response

13 01 2012
Alfonso Llana

What an interesting and seldom seen subject. I enjoyed reading about this. Thanks for posting.

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