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C-4. Cams, cranks and pistons are parts of the engine of a motorbike - Leaving Cert DCG - Question C-4 - 2019
Question C-4
C-4. Cams, cranks and pistons are parts of the engine of a motorbike. (a) The graphic shows an enlarged view of a cam from a motorbike engine. A cam, similar to th... show full transcript
Worked Solution & Example Answer:C-4. Cams, cranks and pistons are parts of the engine of a motorbike - Leaving Cert DCG - Question C-4 - 2019
Step 1
Draw the displacement diagram for the cam
Answer
To create the displacement diagram for the cam, follow these steps:
- 360° Division: Start by dividing the circumference into 360° segments.
- Set Heights: Use a height of 70mm for the rise from 30° to 120° and 14mm for the drop from 120° to 180°.
- Draw Dwell Sections: From 0° to 30°, maintain a horizontal line at 0 height to depict dwell.
- Rise Section: Between 30° to 120°, draw a straight line rising to 70mm.
- Fall Sections: From 120° to 180°, draw a line falling straight down to 14mm, then from 180° to 360°, draw the final drop with simple harmonic motion until reaching 0.
- Final Review: Ensure all segments are correctly labeled and use a scale of 15mm per 30° for accurate representation.
Step 2
Plot the locus of point B for this movement
Answer
To plot the locus of point B for the crank and rod mechanism, follow these steps:
- Set up the Diagram: Start with points O, A, and C as described in the diagram. Point O is the rotation point of crank OA.
- Draw Circle about O: Draw a circle about point O with a radius equal to the length of crank OA.
- Mark Point A: Position point A at the end of crank OA for its initial rotation.
- Locus Creation: As the crank rotates, mark the positions of point B for each relevant angle (45°, etc.) and connect these points to establish the locus of movement.
- Complete the Locus: Continue plotting the positions for each consecutive rotation until the full path of point B is clear.