Simple Machines: Gears, Velocity Ratios and Mechanical Advantage

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# Simple Machines: Gears, Velocity Ratios and Mechanical Advantage - PowerPoint PPT Presentation

Simple Machines: Gears, Velocity Ratios and Mechanical Advantage. What is a simple machine?. A device which uses basic mechanisms to make work easier for the user. Example: Lifting a heavy box with a rope and pulley system

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### Simple Machines: Gears, Velocity Ratios and Mechanical Advantage

What is a simple machine?
• A device which uses basic mechanisms to make work easier for the user.
• Example: Lifting a heavy box with a rope and pulley system
• Simple machines are found in many transportation devices such as the following:
• Cars
• Bicycles
• Trains
What are gears and why are they so useful?
• Gears are toothed wheels which interlock to form simple machines.
• The tighter the joint, the less chance of slipping
• Gears range in size but the important number is how many teeth a gear has.
What is a gear ratio?
• A gear ratio is the ratio between the driver gear (the one being powered) and the driven gear (the one connected to the driver)
• Gear Ratios are expressed as fractions and can be written a number of ways.
• 1 to 3
• 1/3
• 1:3
• Always remember that the driven gear will turn in the opposite direction of the driver gear
What is a pulley?
• A wheel with a grove carved around its circumference in which a rope or belt is placed to drive the wheel.
• Pulleys are used in a number of applications including:
• Elevators
• Cranes
• Automobiles
Drawbacks of Pulleys
• Pulleys work great as long as the belt which connects them is tight and both pulleys are aligned.
• Pulleys tend to slip when too much strain is placed on the system.
How do I calculate my gear ratio?
• A simple equation is used to find the ratio of your gearing system
• Number of Teeth on the Driven Gear / Number of Teeth on the Driver Gear.
• Size of the driver pulley/ Size of the driven pulley
What is Velocity Ratio (VR)?
• When calculating for velocity or speed, it is best to have a ratio in which the driver gear is larger than the driven gear.
• For maximum speed you should always have a larger driver gear/pulley paired with a smaller driven gear/pulley.