Slider-crank linkage

The displacement of the end of the connecting rod is approximately proportional to the cosine of the angle of rotation of the crank, when it is measured from top dead center (TDC).

This difference becomes significant in high-speed engines, which may need balance shafts to reduce the vibration due to this "secondary imbalance".

But in reality, the torque is maximum at crank angle of less than α = 90° from TDC for a given force on the piston.

One way to calculate this angle is to find out when the Connecting rod smallend (piston) speed becomes the fastest in downward direction given a steady crank rotational velocity.

The crank moves in only one direction, provided the position and condition of the slider are not externally altered.

The graphical method of designing an in-line slider-crank mechanism involves the usage of hand-drawn or computerized diagrams.

These diagrams are drawn to scale in order for easy evaluation and successful design.

Basic trigonometry, the practice of analyzing the relationship between triangle features in order to determine any unknown values, can be used with a graphical compass and protractor alongside these diagrams to determine the required stroke or link lengths.

This ground level is the axis on which both the crank arm pivot-point and the slider pin are positioned.

Once the pin positions are correctly placed, set a graphical compass to the given link length of the crank arm.

Next, from the free point on the crank arm, draw the follower link using its measured or given length.

: Its speed (the first derivative of its position) is representable as: Its acceleration (the second derivative of its position) is representable as the complicated equation of: The analytical method for designing an offset crank slider mechanism is the process by which triangular geometry is evaluated in order to determine generalized relationships among certain lengths, distances, and angles.

These generalized relationships are displayed in the form of 3 equations and can be used to determine unknown values for almost any offset slider-crank.

The 3 equations are as follows: With these relationships, the 3 link lengths can be calculated and any related unknown values can be determined.

[2][3][4] A slider-crank is a four-bar linkage that has a crank that rotates coupled to a slider that the moves along a straight line.

When the slider begins to move back into the tube, the connecting rod pulls the wheel round to complete the rotation.