This document describes an experiment to obtain the displacement diagram of a piston in a crank and connecting rod assembly. Students will use a slider crank apparatus to collect data on piston movement over increments of crank rotation and generate graphs of displacement, velocity, and acceleration. The goals are to understand the piston's cyclical motion and determine its maximum displacement, velocity, and acceleration.

1. JJ508
ENGINEERING
LABORATORY 3
MECHANICS OF MACHINE
EXPERIMENT 2
CRANK AND CONNECTING ROD

2. At the end of the lab session students should be able:
To obtain the displacement diagram for the
piston of a crank and connecting rod assembly.
Experiment Outcome

3. i. Slider crank
ii. Set of weights
Apparatus/Equipment

4. Apparatus/Equipment

5.  Decide on the crank radius and the connecting rod length.
 Rotate the crank to check the working of the whole assembly.
 Before taking readings, turn the crank slowly and watch the
movement of the piston. The piston will slide in one direction,
then reverse.
 Locate the position where the piston starts to reverse.
 Use this position as the start point.
Procedures

6.  Use one end of the piston as the marker to measure the piston
movement.
 For accurate result, take small increments of the piston
readings.
 Rotate the crank and record the corresponding piston
movement.
 Take reading for every 5 degrees of the crank rotation.
 Record the readings in the Table provided.
Procedures

7. Result/Data
Crank Reading
θ
Piston
Movement (mm)
Crank Reading
θ
Piston
Movement (mm)
Crank Reading
θ
Piston
Movement (mm)

8. Result/Data
Crank radius = ____ mm
Length of connecting rod = ____ mm
Draw the crank and connecting rod assembly to scale.
 From the data in the Table above plot the piston displacement
diagram.
 Since the velocity is the slope of the displacement diagram use
any known numerical method to determine the slope and plot
the velocity diagram.
 Use the slope of the velocity diagram to plot the acceleration
diagram.

9. i. Describe the type of displacement that the piston
undergoes as the crank rotates.
ii. Find the maximum displacement, velocity and
acceleration.
iii. Why is it important to know the maximum
acceleration?
Discussion

10.  Make your conclusion based on the experimental
displacement diagram.
Conclusion and Recommendation