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.
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.
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.