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A worm and worm wheel mechanism is used to tension the volleyball net shown opposite - Leaving Cert Engineering - Question 8 - 2015
Question 8
A worm and worm wheel mechanism is used to tension the volleyball net shown opposite. (i) Describe, with the aid of a diagram, how the worm and worm wheel mechanism... show full transcript
Worked Solution & Example Answer:A worm and worm wheel mechanism is used to tension the volleyball net shown opposite - Leaving Cert Engineering - Question 8 - 2015
Step 1
Describe, with the aid of a diagram, how the worm and worm wheel mechanism shown may be operated to tension the net.
Answer
The worm and worm wheel mechanism operates by utilizing a worm screw that engages with a worm wheel. As the handle is turned, the worm rotates, which in turn drives the gear wheel attached to it. The gear wheel tightens the net cord by wrapping it around a spool or similar attachment. This mechanism provides precise control over the tension of the net, ensuring it can be properly adjusted for different playing conditions.
Here is a labeled diagram illustrating the mechanism:
Handle
|
|
Worm Screw
|
Worm Wheel
|
Gear Wheel -- Net Cord Attachment
Step 2
Describe, with the aid of a diagram, a suitable method for adjusting the height of the net shown.
Answer
The height of the net can be adjusted using a pin mechanism. This mechanism consists of an outer tube with pre-drilled holes and an inner tube with pins. The outer tube is fixed in position, while the inner tube can slide up or down, allowing the height of the net to be set accurately. By inserting the pin into the desired hole, the operator can secure the net at the appropriate height.
A diagram to illustrate this is:
Graduated Tubular Frame
+-----------------+
| Outer Tube | <-- Fixes position
| |
| (Pin) |
| Inner Tube | <-- Adjusts height
| |
+-----------------+
Step 3
Explain any three of the following: The function of a thermostat.
Answer
A thermostat is a device that monitors and regulates the temperature of a system. It accomplishes this by switching heating or cooling devices on or off to maintain a desired temperature set-point. The function of the thermostat ensures that the conditions within a space remain stable, providing comfort and efficiency in temperature control.
Step 4
Explain any three of the following: The advantages of roller bearings.
Answer
Roller bearings offer several advantages:
- Higher Load Capacity: They can handle radial and axial loads more effectively than ball bearings.
- Ease of Replacement: Roller bearings are generally simpler to replace due to their standard sizes.
- Variety of Sizes: They are available in various dimensions, allowing for flexibility in design.
Step 5
Explain any three of the following: One application of a DPDT switch.
Answer
A Double Pole Double Throw (DPDT) switch is commonly used in electric circuits to control the direction of a motor. By toggling the switch, the current flows in one direction or the other, allowing the motor to operate forward or reverse based on the desired application.
Step 6
Explain any three of the following: Two advantages of helical gears over spur gears.
Answer
Helical gears have distinct advantages compared to spur gears:
- Smoother Operation: They engage gradually due to their angled teeth, resulting in quieter operation and reduced vibrations.
- Higher Load Capacity: The tooth contact is greater, allowing helical gears to handle heavier loads compared to spur gears.
Step 7
Explain any three of the following: The operation of a pneumatic double-acting cylinder.
Answer
A pneumatic double-acting cylinder uses compressed air to move the piston in both directions. When air is supplied to one side of the piston, it pushes it to one end of the cylinder. To return the piston to its original position, air is then supplied to the other side. This allows for controlled movement in both directions and requires pressurized air for operation.
Step 8
A mechanism to move the robot's arm.
Answer
The robot’s arm can be moved using a worm wheel mechanism similar to the one described for the net tensioning. The worm is connected to a driving motor, allowing for precise control. As the motor rotates the worm, it turns the worm wheel, effectively moving the arm upwards or downwards.
Step 9
A mechanism to allow the robot to travel on a flat surface.
Answer
The robot can be designed with gears connected to driving wheels. The arrangement allows the wheels to rotate based on the power delivered from the motor, enabling movement on flat surfaces. This design can include a DPDT switch for directional control; the robot can move forward, reverse or turn as needed.
Step 10
Describe, with the aid of a diagram, the principle of operation of a relay.
Answer
A relay operates as an electromagnetic switch that opens or closes contacts when it receives an electrical signal. It consists of a coil wound around an iron core. When current flows through the coil, it generates a magnetic field that attracts a pivoted armature, causing it to close or open corresponding contacts. This principle allows low voltage circuits to control higher voltage circuits.
A simplistic diagram for a relay:
[Low Voltage Signal] --> [Coil]
Magnetised Iron Core
+--------+
| |
[Contacts Open] [Contacts Closed]
Step 11