Types of pulleys and gears Flashcards
What is a pulley
A pulley consists of a rope and hub or ‘drum’ in which there is a grooved wheel mounted with an axle.
What are the types of pulleys
Fixed, moveable, compound and complex
What is a fixed pulley
Pulley where the drum is secured to one spot. Force required to lift is same, direction that force is applied can change
What is a moveable pulley
One in which the drums moves as you move the load. No change in direction of force, but load ‘feels lighter
What is a compound pulley
in a compound pulley, there is both a moveable pulley as well as a fixe pulley. Load feels lighter + direction can be changed. Disadvantage is more motion is required
What is a complex pulley
A complex system is any system that is a combination of simple and compound systems
What is a gear
A gear or gearwheel is a rotating machine part typically used to transmit rotational motion and/or torque by means of a series of teeth that engage with compatible teeth of another gear or other part.
Types of gears
Spur, bevel, worm, rack and pinion
Spur gears
Spur gears are used to transmit power between two parallel shafts. The teeth on these gears
are cut straight and are parallel to the shafts to which they are attached
Bevel gears
A bevel gear is shaped like a section of a cone and primarily used to transfer power between intersecting shafts at right angles
Worm gears
A gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel. Worm gears are used to transmit power between two shafts that are at right angles to each other and are non-intersecting
Advantages and disadvantages of spur gears
A:
Simple, economical to produce
increase or decrease shaft speed with a high degree of precision at a constant velocity.
D:
High speeds become noisy
take significant stress - not useful in heavy loads
Advantages and disadvantages of worm
Advantages of Worm Gears:
High Reduction Ratio: Provides significant speed reduction and increased torque.
Self-Locking: Prevents back-driving and holds the load in place.
Smooth Operation: Ensures quiet and smooth gear movement.
Compact Design: Achieves high reduction in a small space.
Versatile: Suitable for various applications and power angles.
D:
Yield low efficiency because of high friction
High wear and tear due to friction in high torque applications
Advantages + disadvantages of bevel
Advantages:
Compact Design: Allows for direction changes in a tight space.
High Efficiency: Can achieve high transmission efficiency.
Flexible Angles: Available in various angles, commonly 90 degrees.
Smooth Operation: Provides smoother and quieter operation.
Disadvantages:
Disadvantges
Complex Manufacturing: Requires precise production and alignment.
Higher Cost: Generally more expensive than parallel gears.
Load Capacity: May have lower load capacity due to angled teeth.
Wear and Tear: Can experience more wear if misaligned or poorly maintained.
Why use gears
Prevents slippage and the change of speed, torque and rotational direction
