Understanding Mechanisms: Types and Applications

Mechanisms

Mechanisms are devices that transform movement. They can change the speed, direction, force, or type of movement.

Belts and Pulleys

A belt passes around two pulley wheels. If the driver wheel moves, it moves the belt, and the belt moves the driven wheel.

A pulley is a wheel that turns when a rope, belt, or chain passes through it.

Levers

The lever is a basic mechanism. It's typically made of a bar of wood or metal that pivots around a fixed point called a fulcrum.

• First-type lever Examples: Scissors, pliers, bottle opener, seesaw.
• Second-type lever Examples: Wheelbarrow, paint chippers, nutcrackers.
• Third-type lever Examples: Catapult, baseball bat, human arm.

Effort x Effort arm = Load x Load arm

Questions about levers and pulleys

1. What does a mechanism change?

   Mechanisms change the speed, direction, force, or type of movement.

2. What does the mechanism of a lift change?

   It changes the rotary movement of the electric motor into the linear movement of the cabin.

3. In a belt, which wheel moves faster? Which wheel moves with more force?

   The smaller wheel moves faster. The larger wheel moves with more force.

4. Calculate the effort to move these loads with a double pulley:

   • 160kg : 2 = 80 kg
   • 80kg : 2 = 40 kg
   • 30kg : 2 = 15 kg
   • 25kg : 2 = 12.5 kg

Gears

Gears are toothed wheels that mesh with each other to transmit motion or to change speed, force, or direction.

The driver gear connects to the power source (like a motor). The driven gear connects to the load.

Gears normally reduce speed and increase force.

Gear ratio = (N1 * Z2) / (N2 * Z1)

Where:

• N1: Speed of the driver gear.
• N2: Speed of the driven gear.
• Z1: Number of teeth of the driver gear.
• Z2: Number of teeth of the driven gear.

Types of Gears

• Spur gears: The most common type of gear.
• Bevel gears: Bevel gears have their shafts at ninety degrees. They change the direction of movement.
• Worm gears: They have a great speed reduction ratio, so they are used to significantly slow down a movement.
• Rack and pinion: They typically change rotary motion into linear motion and are used for sliding doors.

Gear Terminology

• Driver gear (engranai gidaria)
• Driven gear (engranai gidatua)
• Spur gears (engranai zuzena)
• Bevel gears (engranai konikoa)
• Worm gear (torloju amaigabea)
• Rack and pinion (pinoi amaiera)

Questions about gears and levers

1. In which type of lever does the load move faster than the effort?

   Always in the third type of lever and sometimes in the first type of lever.

2. What is the difference between the "driver gear" and the "driven gear"?

   The "driver gear" connects to the engine or motor. The "driven gear" connects to the load.

3. Name the advantages and disadvantages of gears compared to belts.

   Gears can transmit more power, but are less flexible, noisier, and the transmission is less smooth.

4. Calculate the speed of the driven gear: Driven gear: 800 rpm; 10mm diameter. Driver gear: 40 mm diameter.

   Speed of driven gear: (800 * 10) / 40 = 200 rpm

5. Think of an example where you would use bevel gears and describe it.

   A roller shutter door (ateak ixteko pertsiana).