Hackworth valve gear

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Hackworth valve gear on steam locomotive 'Lydia' at the Perrygrove Railway.
Hackworth valve gear on Tal-y-Llyn Railway 'Edward Thomas'

The Hackworth valve gear is a design of valve gear used to regulate the flow of steam to the pistons in steam engines. It is a radial gear, with an actuating lever driven from the crank. The drive may be taken directly from the crank (top picture) or indirectly via a return crank (lower picture). The other end of the actuating lever is attached to a die block which slides in a slotted link. When the link is vertical, the engine is in mid-gear. Forward, reverse and cut-off adjustments are made by moving the link away from the vertical. The valve rod is pivoted to a point on the actuating lever.[1]


The gear was patented by John Wesley Hackworth (1820-1891), son of Timothy Hackworth, in 1859.[2]

Klug's valve gear

Hackworth valve gear was a precursor to Klug's valve gear, but it differs from the latter in that the eccentric rod's suspension point moves to-and-fro in a straight line by means of a die block sliding in a slotted guide.[3]

See also


  1. ^ "What is HACKWORTH VALVE GEAR?". Retrieved 15 February 2014.
  2. ^ http://www.steamindex.com/people/hackwort.htm#john
  3. ^ Josefsson, Lars. "Lars Josefsson. Important marine boilers information:". Retrieved 15 February 2014.
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