Crank-connecting rod system

The crank-connecting rod system is a model of mechanism which owes its name at 2 piece-rates which characterize it. It appears at the dawn of the Renaissance and constitutes a Innovation rupture which comes to be added to the five simple kinematic chains inherited the Greek mechanics. Its apparently commonplace kinematics, mask of truths engineering problems: after more than one century of existence, the thermal engine could not find of another alternative for the variation of volume in the combustion chamber. The Rotary engine has still some progress to make. Moreover the car manufacturers balk to give up this low driving which goes and concentrate all their efforts on the admission and the exhaust. The Connecting rod-crank one will thus turn still a little…

Origin

The crank-connecting rod system undoubtedly represents most important Innovation of the 15th century. The German technical thought of this time bequeathed us an anonymous manuscript, dated around 1430, said " Anonymous of the war hussite" ⁽¹⁾. This one comprises several drawings of mills with arms which constitute the first unquestionable illustrated representation of this mechanism: one distinguishes there perfectly the operated rods with arm, and the cranks.

In addition, the technicians probably very quickly realized that there exist two dead points which can block the system, so that they quickly associated a Volant of inertia on the axis of rotation, wheel made up of a wheel or bars at right angles provided with mallets and which constitute the ancestor of the Centrifugal governor .

The crank-connecting rod system allowed the appearance of a mechanization of a new kind, initially of small size with the treadle machines which release the hand of the workman, like the turn, the grinding stone or the wheel (1470). The prohibition of this last, registered a long time in the payments of Corporation S shows how much this innovation was relevant because destabilizing. Will come then from the machines of bigger size actuated by the wheels of the Moulin S, as the hydraulic saw (Francesco di Giorgio Martini), the suction and force pump (XVIe century) or the hydraulic hammer which make it possible to forge parts of great dimension.

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