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Watt's parallel motion on a pumping engine. In previous engines built by Newcomen and Watt, the piston pulled one end of the walking beam downwards during the power stroke using a chain, and the weight of the pump pulled the other end of the beam downwards during the recovery stroke using a second chain, the alternating forces producing the rocking motion of the beam.
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 to the central point of the linkage, allowing it to act on the two outer beams of the linkage both by pushing and ...
The Scott Russell linkage (1803) translates linear motion through a right angle, but is not a straight line mechanism in itself. The Grasshopper beam/Evans linkage, an approximate straight line linkage, and the Bricard linkage, an exact straight line linkage, share similarities with the Scott Russell linkage and the Trammel of Archimedes.
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The second is the parallel motion, which converts the up-and-down motion of the piston into the arcing motion of the beam, whilst maintaining a rigid connection. The rigid connection allowed the engine to be double-acting, meaning the piston could push as well as pull the beam.
In the study of mechanisms, a four-bar linkage, also called a four-bar, is the simplest closed-chain movable linkage. It consists of four bodies, called bars or links, connected in a loop by four joints. Generally, the joints are configured so the links move in parallel planes, and the assembly is called a planar four-bar linkage. Spherical and ...
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 ...
According to F. Lisheng and T. Qingjun, the hand-crank of the rotary quern was different from a crank, which was the combination of a hand-crank and a push-and-pull connecting rod by a hinge. [ 7 ] The Antikythera mechanism, dated to around 200 BC, [ 25 ] [ 26 ] used a crank as a part of its mechanism. [ 27 ]