Motion Monday Inverted Slider Crank in Series with Slider Crank

KG 2026-03-09

Hello everyone, 👋

Welcome back to Motion Monday! This time for real 😁 , Recently I saw an interesting kinematic combination — the inverted slider crank in series with a slider crank — and thought of sharing a quick note on it.

It is basically a combination of two mechanisms connected one after the other.

A slider crank mechanism converts rotary motion into reciprocating motion.
An inverted slider crank mechanism is a variation where the slider is fixed and another link produces oscillatory motion.
When connected in series, the rotary output of the first mechanism drives the oscillatory motion in second, giving a modified and more controlled motion.

In this mechanism, there are 4 rigid links, 3 lower pairs (surface contact), and 2 higher pairs (point or line contact).

Using Gruebler’s equation for planar mechanisms:

DOF=3(n−1)−2L−H

DOF=3(n−1)−2L−H

where

n = number of links
L = number of lower pairs
H = number of higher pairs

Substituting the values:

DOF=3(4−1)−2(3)−2

DOF=9−6−2

DOF=1

This means the mechanism has one degree of freedom, and its motion can be completely controlled by a single input, i.e. the rotation of the crank.

Motion transformation in the mechanism:

Input: Rotary motion (360 Degrees, 100 rpm)
Intermediate: Oscillatory motion (angular displacement θ=61.78 degrees)
Output: Reciprocating motion (slider displacement 154.5mm)

To Play with the motion yourself you can download SOLIDWORKS file from below.

3DPLAY Model
Exploded View
Motion Analysis
SOLIDWORKS Zip File

Edu MotionMonday