Mechanical Gears and Energy Transfer

Technology 8

What is energy?

• Energy is the ability to do work.

• Energy can be– Kinetic- the energy of motion.– Potential- “waiting” energy.

Kinetic and Potential Energy

Some Types of Energy

• Chemical (food energy)

• Light (solar)

• Electrical (electrons moving through wires)

• Mechanical (movement of objects)

• Nuclear (energy in nucleus of an atom)

First Law of Thermodynamics

• Energy cannot be created nor destroyed.

• Energy can be transferred.

Mechanisms

• Can be used to change energy by transferring its direction, speed, type of movement and force or torque.

• Common mechanisms are:– Bicycle– Eggbeater

• Mechanisms can work alone, in pairs, or systems.

Gears

• Gears redirect the applied force so that mechanisms can accomplish their tasks.

• Gears come in all sizes.

• Some gears are covered, some aren’t.

• Some require a lot of maintenance, some very little.

Input

• Each mechanism has an initial force which starts the “working process”.

• This is the input.

Output

• The motion and force which occurs as a result of the input.

Uses of gears

• Gears or pulley systems allow a change in speed, torque, force, type of movement and direction.

• This is a common problem in automobiles, airplanes, robots and mechanical tools.

Force

• That which causes an object with mass to accelerate.

Torque

• A force that causes a rotation around a central point, such as an axis.

Relationship Between Torque and Speed

• There is an “opposite” relationship between torque and speed.

• Increase in torque means decrease in speed.

• Decrease in torque means increase in speed.

Calculating Gear Ratios

• Gear Ratio = # of teeth on output gear / # of teeth on input gear

• As the size of the driven gear decreases in relation to the size of the driving gear, output speed increases.

• As the size of the driven gear increases in relation to the driving gear, output torque increases.

Hand Mixer: Crown & Pinion Gear

Electric Motor: Gear Train

Antique Jack: Bevel Gear and Worm Gear

Ice Cream Scoop: Rack & Pinion

Paper Transport Rollers Simple Gear Train with Idler

Stapler: Multiple Mechanisms

Toy Telephone: Rack & Pinion

Rearview Mirror Motors: Rack & Pinion

Fishing Reel: Crown & Pinion

Electric Mixer: Worm & Wheel

Food Processor: Planetary Gears