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The World’s Largest Deadweight Machine is Getting a Bath


The National Institute of Standards and Technology (NIST) is in the process of cleaning, restoring and recalibrating its 4.45-million Newton deadweight machine. Known to be the largest in the world, that’s equivalent to one million pounds-force. This is the first time in 50 years the NIST has dismantled the weight stack. Dismantling the top half of the three-story stack of weights, is now complete and the individual pieces are being cleaned in preparation for recalibration.

A deadweight machine is a mechanical structure that generates force by subjecting deadweights to the local gravitational field. Deadweight machines are used for precise definition of the force scale. NIST’s machine is used by U.S. aerospace manufacturers, U.S. military laboratories, and several top-end commercial force calibration labs, which have performed hundreds or thousands of calibrations, all directly traceable to NIST.

Built in 1965, the deadweight system consists of a stack of 20 stainless steel discs about three meters in diameter (a little less than ten feet) when assembled. Their average mass is about 22,696 kg (just over 50,000 pounds) each.

In addition to cleaning and recalibration, some of the surfaces deep within the weight stack are being restored by minor machining to permit more free operation at those interfaces. Theorists are also modeling the stack to give researchers insight into the deflections occurring where the stresses are highest.

Dismantling the weight stack took several weeks, because each piece had to be unbolted and carefully lifted with a series of cranes.

Please watch this video for highlights of the disassembly process:

The deadweight machine is expected to be operational again later this year.