Crank handle

Gear links of the slider crank

Slider crank in a gasoline engine

Slider crank, animated: blue arrows = velocity vectors of mass points

The slider crank (the slider crank mechanism ) is the most common of the coupling mechanisms combined in the slider crank chain .

It is used to convert a rotary movement into an oscillating pushing movement or vice versa. The equation of motion x (φ) reads (see adjacent figure):

${\displaystyle x=l_{1}\cdot \cos \varphi +l_{2}\cdot {\sqrt {1-\left({\frac {l_{1}}{l_{2}}}\right)^{2}\cdot \sin ^{2}\varphi }}}$

The push rod ratio is also referred to as λ. In case for this ${\displaystyle {\frac {l_{1}}{l_{2}}}}$

${\displaystyle \lambda ={\frac {l_{1}}{l_{2}}}\ll 1}$

holds, then the above formula simplifies to:

${\displaystyle x=l_{1}\cdot \cos \varphi +l_{2}}$

The most famous application of the slider crank is the piston engine . The push member is the piston that moves back and forth in the cylinder . This transmits its longitudinal movement to the rotary output, the crankshaft , via the connecting rod . Piston pumps and steam engines with slider cranks have been around for a long time .

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