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In kinematics, the parallel motion linkage is a six-bar mechanical linkage invented by the Scottish engineer James Watt in 1784 for the double-acting Watt steam engine. It allows a rod moving practically straight up and down to transmit motion to a beam moving in an arc, without putting significant sideways strain on the rod.
Such an engine incorporates a piston acted upon by steam alternately on the two sides, hence doubling its power. The linkage actually used by Watt (also invented by him) in his later rotary beam engines was called the parallel motion linkage, a development of "Watt's linkage", but using the same principle. The piston of the engine is attached ...
Another important invention, one which Watt was most proud of, was the parallel motion linkage, which was essential in double-acting engines as it produced the straight line motion required for the cylinder rod and pump, from the connected rocking beam, whose end moves in a circular arc. This was patented in 1784.
Watt's parallel motion on a pumping engine. The first Watt engines were atmospheric pressure engines, like the Newcomen engine but with the condensation taking place separate from the cylinder. Driving the engines using both low pressure steam and a partial vacuum raised the possibility of reciprocating engine development. [11]
1783 (): Watt builds his first "double acting" engine, which admits steam so as to alternately act on one side of the piston then on the other, and the introduction of his parallel motion linkage allows the transmission of the power of the piston motion to be transmitted to the beam on both strokes.
Linkage mobility Locking pliers exemplify a four-bar, one degree of freedom mechanical linkage. The adjustable base pivot makes this a two degree-of-freedom five-bar linkage. It is common practice to design the linkage system so that the movement of all of the bodies are constrained to lie on parallel planes, to form what is known as a planar ...
A later variant of the Cornish Engine is the Bull engine, which dispenses with the beam by having the cylinder mounted directly over the pump leading to significant valve gear differences. As one source describes . Driving a Cornish beam engine is tricky enough but the Bull is a different kettle of fish altogether.
This category is for beam engines, most of which are steam-powered, although some ... Parallel motion linkage; R. Rotative beam engine; S. Six-column beam engine; T ...