# Mechatronics Questions and Answers – Mechanical Actuating Systems – Ratchet and Pawl

This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Mechanical Actuating Systems – Ratchet and Pawl”.

1. Who invented Ratchet wrench?
a) Grueblerowen
b) Vitaly Abalakov
c) Robert Owen
d) Robert Abalakov

Explanation: Robert Owen invented Ratchet wrench. Ratchet wrench is also known as socket wrench. It is widely used hand tool made for tightening or loosening of nuts and bolts present in furniture, electronics equipment etc.

2. What is the purpose of pawl, when it is used against a ratchet which is attached to a shaft?
a) It allows unidirectional motion of shaft
b) It allows bidirectional motion of shaft
c) It does not allow motion of shaft
d) It is used to create additional friction force for the shaft

Explanation: The purpose of pawl, when it is used against a ratchet which is attached to a shaft is that; it allows unidirectional motion of shaft. It restricts the motion in other direction. When the shaft tries to move in other direction then the pawl encounters the steeper slope of the ratchet which completely stops the rotational motion.

3. What is the minimum number of tooth, a ratchet should have?
a) 2
b) 4
c) 8
d) 0

Explanation: It is not necessary for a ratchet to always have toothed surface. So the minimum number of tooth, a ratchet should have is zero. The surface of these ratchets is made with materials that have high coefficient of friction.

4. Which ratchets are often called as roller drive ratchets?
a) 72 teeth ratchet
b) Stepless ratchets
c) Round ratchet
d) Flip ratchet

Explanation: Stepless ratchets are often called as roller drive ratchets. They are also popularly known as gearless ratchets. The name itself suggests that they don’t have teeth. These ratchets are often used during the tightening or loosening of very small and slippery nuts and bolts.

5. The tooth of a ratchet is symmetrical.
a) True
b) False

Explanation: The tooth of a ratchet is asymmetrical. Ratchets are toothed-wheels similar to the structure of gears; but they have asymmetrical tooth unlike gears. On one side of the tooth the slope is moderate while the other side has steeper slope.
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6. The movement of the ratchet can be locked by pawl if it moves in opposite direction.
a) True
b) False

Explanation: The movement of the ratchet can be locked by pawl if it moves in opposite direction. Ratchets have asymmetrical tooth unlike gears; on one side of the tooth the slope is moderate while the other side has steeper slope. When the ratchet moves in opposite direction the pawl encounters the steep side of the tooth; therefore it cannot slide further and gets locked.

7. What is the maximum distance, a pawl can travel during the backward motion of a ratchet?
a) It is equal to the distance between two alternating teeth
b) It is equal to the distance between two adjacent teeth
c) It is equal to the radius of the ratchet
d) It is equal to the perimeter of the ratchet

Explanation: The maximum distance, a pawl can travel during the backward motion of a ratchet is equal to the distance between two adjacent teeth. When the ratchet moves in opposite direction the pawl encounters the steep side of the tooth; therefore it cannot slide further and gets locked. So the maximum distance it can travel is the distance between two adjacent teeth.

8. Who invented Ratchet wheel, which was further used in power loom?
a) Grueblerowen
b) Vitaly Abalakov
c) Robert Owen

Explanation: William Radcliffe invented Ratchet wheel, which was further used in power loom. He was born on the year 1760. He invented the ratchet wheel for his power loom which moved the cloth piece forward automatically.

9. What is the purpose of pawl, when it is used against a spur gear which is attached to a shaft?
a) It allows unidirectional motion of shaft
b) It allows bidirectional motion of shaft
c) It does not allow motion of shaft
d) It is used to create additional friction force for the shaft

Explanation: The purpose of pawl, when it is used against a spur gear which is attached to a shaft is that; it does not allow motion of shaft. It will restrict the motion in both directions. When the shaft tries to move in any of direction then the pawl encounters the steeper slope of the spur gear which completely stops the rotational motion.

10. What does “12-point” indicates when the term 12 point reversible ratchet is used?
a) Its diameter is 12
c) It has 12 teeth
d) Its pitch is 12

Explanation: When the term 12 point reversible ratchet is used,the term “12-point” indicates that the ratchet or the gear mechanism used in the device has 12 teeths. The more the number of teeth; the smaller movements a device can achieve.

11. Ratchet screw driver can apply turning force in one direction only.
a) True
b) False

Explanation: Ratchet screw driver can apply turning force in one direction only. They are made in such a way that their mechanism allows it apply turning force in one direction only. Whereas it can move freely in opposite direction.

12. Backlash of a ratchet is the maximum distance covered by the pawl when the ratchet moves in opposite direction.
a) True
b) False

Explanation: Backlash of a ratchet is the not maximum distance covered by the pawl when the ratchet moves in opposite direction. It refers to the motion, when the ratchet moves in opposite direction and the pawl covers the maximum distance.

13. It is not necessary to have teeth on the surface of the ratchet.
a) True
b) False

Explanation: It is not necessary to have teeth on the surface of the ratchet. For reducing the backlash, often toothless ratchets are used. The surface of these ratchets is made with materials that have high coefficient of friction.

14. Which ratchets are often called as reversible ratchets?
a) 72 teeth ratchet
b) Stepless ratchets
c) 3 way ratchet
d) Flip ratchet

Explanation: 3 way ratchets are often called as reversible ratchets. These ratchets facilitate the customer with three different configurations. One configuration will disengage the ratchet configuration while the other two configurations allow the movement of the ratchet in either clockwise or anti-clockwise direction.

15. What is the difference between ratchet and spur gear?
a) Ratchets have bigger diameter than spur gear
b) Ratchets have lesser diameter than spur gear
c) Ratchets have asymmetrical tooth but spur gear have symmetrical tooth
d) Ratchets have symmetrical tooth but spur gear have asymmetrical tooth

Explanation: The difference between ratchet and spur gear is that Ratchets have asymmetrical tooth but spur gear have symmetrical tooth. The asymmetrical shape of the tooth allows pawl to restrict the bidirectional movement of the ratchet.

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