1.0 Objective
To determine the linear velocity of the slider through theory and experiment when the angular velocity of the crank is set to 2.0 rad/s.
2.0 Introduction
In this laboratory, we investigate the kinematics of a simple mechanism used to convert rotary motion into oscillating linear motion and vice-versa. The bench-top unit demonstrates conversion of smooth rotary motion into reciprocating motion. The input angle is set on the crank plate and the slider displacement is read from the measuring scale.
The crank radius can be adjusted to different positions. A simple bolt insertion enables the swiveling cylinder to be locked, allowing demonstration of crank drive behavior.
3.0 Apparatus
Crank and connecting rod apparatus.
Figure 1: Simple crank and connecting rod sketch
4.0 Kinematic Analysis
There are three types of planar rigid body motion:
Translation
Translation occurs if every line segment on the body remains parallel to its original direction during the motion. When all points move along straight lines, the motion is rectilinear translation. When curved, the motion is curvilinear translation.
Rotation about a fixed axis
All particles of the body, except those on the axis of rotation, move along circular paths in planes perpendicular to the axis of rotation.
General plane motion
The body undergoes both translation and rotation. Translation occurs within a plane and rotation occurs about an axis perpendicular to this plane.
Slider-crank relationships
Geometry
r = 25.0, 37.5, 50.0 mm • L = 150.0 mmDisplacement (theoretical)
x = r cosθ + √(L² − r² sin²θ)Velocity (theoretical)
&xdot; = r · x · sinθ · ωr cosθ − xVelocity (experimental)
&xdot; = dxdθ · ωω = 2.0 rad/s
5.0 Procedure
1. Set the crank radius (r) to the specified length.
2. Attach the connecting rod (L) to the slider.
3. Rotate the crank to 0° (Top Dead Center) and zero the gauge.
4. Rotate crank in 30° increments and record slider displacement (x).
5. Repeat for full 360° revolution.
6. Plot Displacement vs. Angle curve.
6.0 Result
Complete tables, plot x vs θ, determine dx/dθ, and compare
Angular velocity
ω = 2.0 rad/s
Enter experimental x in cm in Table 2. The page auto-computes dx/dθ, experimental velocity, and percentage error.
Table 1: Theoretical Values
| θ (°) | x (cm) | &xdot; (cm/s) |
|---|
Table 2: Experimental Data
| θ (°) | x (cm) | dx/dθ (cm/rad) | &xdot; (cm/s) |
|---|
Table 3: Percentage Error (Velocity)
| θ (°) | % error |
|---|
Plot: x (cm) vs θ (deg)
7.0 Discussion
- Explain how a crank and slider system works.
- Compare and discuss the result from the theoretical and experimental tables.
- Give your comment or suggest any cause of errors.
- Explain some practical applications of a crank and slider mechanism.
8.0 Conclusion
Write your conclusion about the experiment.
9.0 References
List all the references that you have made during the course of your findings.
Mechanism Simulation & Game
Angle
0°
Disp
0.0mm
Dead Center Challenge
How to play: Click "Spin" — the crank rotates automatically at varying speed. Click "Stop" to halt it.
Goal: Stop as close to TDC (0°) or BDC (180°) as possible.
Scoring: Within ±5° = +100 pts • Within ±15° = +50 pts • Otherwise = 0 pts
TDC = Top Dead Center (0°) • BDC = Bottom Dead Center (180°)
Your Score
0 pts
Real-World Applications
Where Do You See It?
Slider-crank mechanisms quietly power many everyday machines: from car engines and refrigeration compressors to hand-operated pumps and punching presses.
- Car engines: crankshaft converts piston motion into wheel torque.
- Compressors: pistons draw in and compress air or refrigerant.
- Hand pumps & jacks: your hand motion becomes lifting force.
- Sewing machines: foot pedal rotation drives the needle up and down.
- Locomotive wheels: connecting rod links wheel rotation to piston in steam engines.
Mini Quiz
Everyday Machine Match
Read the scenario and tap the device that MOST likely uses a slider-crank mechanism. Test your understanding of real-world applications!
Assessment Matrix
| Laboratory Item | Score 5 (9-10) | Score 4 (7-8) | Score 3 (5-6) | Score 2 (3-4) | Score 1 (0-2) |
|---|---|---|---|---|---|
| 1. Org & Appearance | Perfect sequence. Diagrams intact. Slips correct. Cover bound. Single PDF. | Format good. Tidy. 1 detail missing. Tape ring bound. | Rough format, organization uneven. Multiple language mistakes, stapled. | Sloppy, damaged inserts. Torn slips, whiteout, staples poorly. | Absent. |
| 2. Objectives & Theory | Rephrased clearly, own sentences. Linking course research included beyond manual. | Objectives identified, sharp manual paraphrase. | Objective partial definition, manual copy. | Verbatim manual, minimal research, objectives missing. | Absent. |
| 3. Apparatus | List machine labeled diagram, own words. Safety photo included, report attached. | Vital items, minor omission, manual paraphrase. | Partial list, omissions, key missing, difficult steps. | Equipment missing, confused, unnumbered, manual copy. | Absent. |
| 4. Results (x2) | Accurate, organised trends clearly. Figures numbered with captions and walkthrough. | Correct trends drawn, obvious minor figure problems/units. | Missing data, sloppy, inaccuracy, incomplete tables. | Figures bad, numbers construct poor construction. | Absent. |
| 5. Discussion (x2) | Answers all accurately. Links trends/outcomes/theory/objectives. Error analysis included. | Miss one answer correctly. Results interpret gap. | Incomplete understanding, partial evident inconsistencies. | Lack understanding, no indicators comparison. | Absent. |
| 6. Conclusion | Summary of data achieved. Valid validity, suggests improvement. | Missing one condition, excellently met. | Missing element, condition met. | Missing conditions. | Absent. |
| 7. References | Multiple sources: journal, book, manual. 30% references < 5 years. | 6-8 sources written, manual observed. | 3-5 format, comply partial compliance. | 1-2 cited, ignore formatting reference standard. | No references. |
Performance Log
Complete Section 6.0 tables and write-ups (7.0–9.0), then preview/export your PDF submission here. Game + quiz marks are included automatically.
Marks Summary
Games
0
Pts
Quiz
0/0
0%
Export Report
Includes tables (6.0) + marks (games and quiz).