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Engineering Report
UNIVERSITY OF WOLLONGONG
Department of Civil and
Mining Engineering.
REPORT ON THE KNEELSIT BALANCE CHAIR
Loads were placed on the seat, generally in 25 kg increments, up to a maximum load of 185 kg (almost 30 stone). The deflection of the frame was measured as shown in Appendix 1, and is the maximum deflection within the frame.
The deflection versus loading line was linear, thus indicating that the frame was within the elastic limit whilst loaded. A settlement of 2 mm for the wheeled supports occurred at a load of 130 kg and the wheel system remained in that position thereafter.
Some deflection (up to 5 mm) did occur in the lower horizontal section of the frame as indicated in Appendix 1, the frame almost touching the ground with 185 kg applied.
The maximum deflection measured was 29 mm at the load of 185 kg; this equated to a deflection of approximately 1.5 mm/10 kg. of applied body weight whilst the seat is positioned furthest away from the structural frame and in its 'worst' (structurally) position.
No sideways deflection of the structural frame was noted.
Other appurtenances on the system were inspected and load tested by hand, these including the adjustable back support, the under seat steel framing and the knee support system; the knee support system can be rotated out of the way to allow of easy movement away from the Equipoise. It is considered that they all are of sufficient strength and rigidity as to support loads of up to 185 kg.
COMMENTS
Overall, the Kneelsit system examined is of satisfactory structural design, capable of supporting persons up to 185 kg. With considerable usage, the wheeled supports on the system could fail due to rough surfaces. A failure of one or more of these wheels would not contribute to a fall as the frame itself would rock or distort such that it lowered by approximately 8 mm until the frame rested on the ground, thus giving full support to the body weight applied thereto.
Associate Professor R W Upfold
Appendix 1
"I weigh over 300 lbs. and suffer from
spondylitis, I bought one of the early models of the chair about 8 years
ago, then after using it for a couple of weeks I bought several more
chairs for my staff. Recently, under extreme pressure, I worked 104
hours in 7 days at the computer, though exhausted at the end I experienced
no backache"
Ken,
Desktop Publisher
Bomaderry.
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