Simple & Powered Machines Set

Pawl and Ratchet

Pawl and ratchet is a simple machine that is used in connection with gear mechanisms to allow linear or rotary motion in only one direction.

30-45 min.
Beginner
Grades 6-8
pawl-and-ratchet

Connect

5-10 Minutes

A ratchet mechanism is based on a gear wheel and a pawl that follows as the wheel turns.

Did you know?
There are ratchets in some screw drivers that allow the user to turn with an effort in one direction and then turn back without turning the screw.

pawl-and-ratchet-model

When the gear is moving in one direction, the pawl slides up and over the gear teeth, sending the pawl into the notch before the next tooth. The pawl is then jammed against the depression between the gear teeth, preventing any backwards motion.

Ratchet mechanisms are very useful devices for allowing linear or rotary motion in only one direction.

Common examples of ratchets are clocks, jacks, and hoists.

Construct

5-10 Minutes

Build the following models. Use the Contemplate ideas below and on the Student Worksheet to learn about each model, one at a time.
Build I1 book III, page 28 to 29

principles-building-instructions-one

Contemplate

10-15 minutes

I1
This model shows a pawl and ratchet gearing. When the handle is turned in one direction, the pawl slides up and over the gear teeth, sending the pawl into the depression before the next tooth. When the handle is turned in the opposite direction, the pawl stops the movement.

pawl-and-ratchet-one

Continue

Try other lessons!
Now that you have mastered the principles of pawl and ratchets try some of the other lever lessons like Windmill.

Teacher Support

Students will learn about:
Pawl and ratchet gearing
Linear or rotary motion in only one direction

9686 Simple & Powered Machines Set (two students per set recommended)

Student Material

Student Worksheet

Download to view and share the student worksheet.

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