How Scotch Yoke Mechanism Works!

The Scotch yoke mechanism also known as  slotted link mechanism is used to  convert the linear motion of a slider  into a rotational motion it can also be  used to convert the rotational motion  into a linear motion  it consists of a slider or a piston a  sliding yoke with a slot  a disc-shaped crank with a pin .

The piston or other reciprocating part  is directly coupled to a sliding yoke  with a slot that engages a pin on the  rotating part when the crank rotates  about a fixed axis the sliding yoke  follows a linear path oscillating  between the two extreme positions  thus the rotational motion of the crank  is converted into a linear motion of the  piston .

The advantages of this mechanism  compared to a standard crankshaft and  connecting rod setup are higher torque  output with a small cylinder size fewer  moving parts and hence smoother  operation higher percentage of the time  spent at top dead center improving the  engine efficiency .

The disadvantages are rapid wear of the  slot in the yoke caused by sliding  friction and high contact pressures  lesser percentage of the time spent at  bottom dead center reducing blowdown  time for two-stroke engines