2.2.1 Mechanisms
What is a mechanism? /
  • A mechanism is the part of a machine that contains two or more pieces arranged so that the ______of one drives the motion of the others.

How are mechanisms used? /
  • Change the ______of movement
  • Change the ______of movement
  • Change the ______of movement
  • Change the amount of ______.

What kind of movement can mechanisms create? /
  1. Reciprocating
  2. Oscillating
  3. Rotary
  4. Linear

What is rotary motion?

What is oscillating motion?

What is linear motion?

What is reciprocating motion?

How does motion affect gears?
/
  • A gear train is a mechanism used for transmitting rotary motion and torque. Gears transmit rotary motion through interlocking teeth.
  • A gear train is made when two or more gears are ______.
  • Meshed gears always turn in ______directions.
  • Energy ______causes the ______ gear to move
  • Energy is transferred to the______gear called the ______ gear

How does gear ratio affect motion? /
  • Gear ratios compare the input drive gear to the output driven gear.
  • The input gear ______the energy to the output gear.
Example:
In the time the input (drive) completes 1 revolution, the output (driven) completes 2, then the gear ratio is 1:2.
How do you calculate the gear ratio? / You need to know one of the following variables for each gear:
  1. n = ______
  2. d = ______
Make sure to reduce!
Example:
Nin: Nout 36:24 3:2
Din: Dout 10:5 2:1

Practice

# Teeth Input gear / # Teeth output gear / Gear
Ratio / Explanation
8 / 40 / 40:8 or 5:1 / The input (drive) gear must turn 5 times to move the output (driven) gear once. Torque increases.
36 / 4
6 / 48
16 / 20
What is force? / A force is a push or a pull in ______.

What is torque? / Torque is a push or pull in ______.

How does torque affect speed? / Gears turn in a circular direction. There is an ______relationship between torque and speed in gearing.
This means:

> (more) speed <speed
<(less)torque > torque
Example:

A ten-speed bicycle has ten different gear selections. When you pedal up a hill, you use a gear train that provides more torque (turning force) but, in doing so, less speed. When you pedal on flat land, you use a gear train that provides more speed, but in doing so, less torque within the gear train. When pedaling up a hill, we tradeoff speed for torque. In other words a reduction in speed is a trade-off to increase torque and make pedaling easier.
How does the size of the gear affect motion?
/ •As the size of the driven gear ______in relation to the size of the drive gear, output speed ______.
•As the size of the driven gear ______in relation to the size of the drive gear, output torque ______.
This means:
bigger gear=more ______
smaller gear= more ______
Practice:
  1. The gear train in which diagram provides more torque? _____
  2. The gear train in which diagram provides more speed? _____
  3. Which gear train would you use to ride up a hill?_____

Practice:List 5 different mechanisms in the Rube Goldberg picture above and predict the purpose of each. Does the mechanism change speed, force, torque, direction, or type of movement? Put a number on the picture to indicate location.

Mechanism Location / Purpose
1.
2.
3.
4.
5.

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GTT-AR VEX Activity 2.2.1Observing Mechanisms– Page 1