J.M. Gabrielse

Torque

J.M. Gabrielse

Outline

fun with seesaws

• two little people

•a big person and a little person

• two little people in different spots

equation

example

J.M. Gabrielse

What Will Happen?

Nothing

J.M. Gabrielse

The Bigger Torque Wins

In this case the torques are equal

so they balance out.

J.M. Gabrielse

What Will Happen?

Why?

J.M. Gabrielse

The Bigger Torque Wins

The BIG FORCE creates a bigger torque than the little force. F

F

A force is a push or a pull.

J.M. Gabrielse

Why?

What Will Happen?

J.M. Gabrielse

F F

Both forces are the same size.

The BIG DISTANCE from the pivot point creates a bigger torque than the little

distance.

The Bigger Torque Wins

(pivot point = fulcrum)

J.M. Gabrielse

What Will Happen?

J.M. Gabrielse

The Bigger Torque will Win

Which torque will be bigger?

a little force with a BIG DISTANCE

a BIG FORCE with

a little distance F

F

J.M. Gabrielse

T = F dNote: d is measured perpendicular to F

distance

Calculate Torque (T)

F

pivot point

d

force

J.M. Gabrielse

What Will Happen?

F = 200 lb

d = 10

F = 50 lb

d = 70 in

J.M. Gabrielse

Use the Equation

F = 200 lb

d = 10 in

T = 2000 in lb

F = 50 lb

d = 70 in

T = 3500 in lb F

F

J.M. Gabrielse

T = 2000 in lb T = 3500 in lb

The Bigger Torque Wins

J.M. Gabrielse

d2d1

Which arm has more torque on it?

Arm 1

Arm 2

F1 = 10 lbs

F2 = 10 lbs

J.M. Gabrielse

d2d1

Which arm has more torque on it?

Arm 1

Arm 2

F1 = F2

d1 > d2

- so -

T1 > T2

F1 = 10 lbs

F2 = 10 lbs

J.M. Gabrielse

Motors Provide Torque

Torque from the motor makes the wheel spin.

The maximum torque from a Vex motor is 6.5 in*lb.

J.M. Gabrielse

Motor Example

How much torque would the motor need to supply?

pivot point

d = 15 in

F = 0.225 lb

motor

T = F d = 0.225 lb x 15 in

J.M. Gabrielse

Motor Example

How much torque would the motor need to supply?

pivot point

d = 15 in

F = 0.225 lb

motor

T = 3.375 in lb

J.M. Gabrielse

Motor Example

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

pivot point

d = 15 in

F = 0.225 lb

motor

J.M. Gabrielse

Can’t loosen a screw?

J.M. Gabrielse

You need more TORQUE!

Push harder (more force)-or-

Use the long side of the allen wrench (longer distance)

J.M. Gabrielse

Two ways to hold an Allen wrench

• Speed: fast Torque: low

• Speed: slow Torque: high

J.M. Gabrielse

Use Torque to Tighten Screws

Or your robot will end up like this!

J.M. Gabrielse

Resources

• http://www.education.rec.ri.cmu.edu/roboticscurriculum/vex_online/lessons/mechanics/torque/mechanics_torque.html

• Inventor’s Guide: 3·10