NC State Chair Racking Test

The purpose of this test is to evaluate the ability of the chair to withstand stresses that occur as the result of the user rocking backward and forward in the chair. This test cycles the chair through 30,000 repetitions while monitoring changes in the angle between the seat rail and the back post. The chair, loaded with a 150 pound hinged weight, is first rocked back until the front legs are raised six inches off of the ground, then rocked forward until the back legs are raised two inches.

The specifications of this test were developed by NC State and it is currently prescribed by the State of North Carolina for suppliers of classroom chairs. The following two videos show the chair racking test being performed on one of the FMM Center's chair testing machines.  As illustrated during the test on the metal chair, the motion can be stopped periodically to obtain intermediate readings from electronic inclinometers mounted at critical locations.
 

Wood Chair  AVI File (1862K) Quick Time Movie (1729K)
Metal Chair  AVI File (2839K) Quick Time Movie (2370K)
 
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