Torque

1
Torque
2
Outline

• fun with seesaws
• two little people
• a big person and a little person
• two little people in different spots
• equation
• example

3
What Will Happen?
Nothing
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The Bigger Torque Wins
In this case the torques are equal so they
balance out.
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What Will Happen?
Why?
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The Bigger Torque Wins
A force is a push or a pull.
The BIG FORCE creates a bigger torque than the
little force.
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What Will Happen?
Why?
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The Bigger Torque Wins
Both forces are the same size. The BIG DISTANCE
from the pivot point creates a bigger torque than
the little distance.
(pivot point fulcrum)
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What Will Happen?
10
The Bigger Torque will Win
Which torque will be bigger?
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Calculate Torque (T)
T F d
distance
force
F
Note d is measured perpendicular to F
d
pivot point
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What Will Happen?
F 200 lb d 10
F 50 lb d 70 in
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Use the Equation
F 200 lb d 10 in T 2000 in lb
F 50 lb d 70 in T 3500 in lb
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The Bigger Torque Wins
T 3500 in lb
T 2000 in lb
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Which arm has more torque on it?
Arm 2
F2
Arm 1
d2
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Which arm has more torque on it?
F1 F2 d1 gt d2 - so - T1 gt T2
Arm 2
F2
Arm 1
d2
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Motors Provide Torque
Torque from the motor makes the wheel spin. The
maximum torque from a Vex motor is 6.5 inlb.
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Motor Example
d 15 in
motor
pivot point
F 0.225 lb

• How much torque would the motor need to supply?

T F d 0.225 lb x 15 in
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Motor Example
d 15 in
motor
pivot point
F 0.225 lb

• How much torque would the motor need to supply?

T 3.375 in lb
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Motor Example
d 15 in
motor
pivot point
F 0.225 lb

• The motor has more than enough torque to lift a
  tube, but it also has to lift the weight of the
  arm.

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Cant loosen a screw?
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You need more TORQUE!
Push harder (more force)-or-Use the long side
of the allen wrench (longer distance)
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Two ways to hold an Allen wrench

• Speed fast Torque low
• Speed slow Torque high

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Use Torque to Tighten Screws
Or your robot will end up like this!
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Resources

• http//www.education.rec.ri.cmu.edu/roboticscurric
  ulum/vex_online/lessons/mechanics/torque/mechanics
  _torque.html
• Inventors Guide 310