society > occupation and work > equipment > machine > parts of machines > shaft > [noun] > rock
rock shaft1833
weigh-bar1841
rocker shaft1842
weigh-shaft1867
1841 Civil Engineer & Architect's Jrnl.4 93/1 A lever is fixed upon the cross-head working in a link connected to a second lever fixed on a shaft or weigh-bar across the engine, whereby a rocking motion is produced.
1890 W. J. GordonFoundry 16 Beam-engine with its weigh-bar gearing.