Which of the following types of the gear set is used to change rotary into linear movement and vice versa?

Explanation:

• Rack and pinion can convert motion from rotary to linear or from linear to rotary.
• A rack and pinion gear system is composed of two gears.
• The normal round gear is the pinion gear and the straight or flat gear is the rack.
• A perfect example of this is the steering system on many cars.

Bevel Gear: 

• Bevel gears are used to transmit motion between shafts at various angles to each other.
• The teeth profile may be straight or spiral.

Hypoid gears 

• The hypoid gears are used in automobile differential gearboxes. 
• The tooth action between each gear is a combination of rolling and sliding action along the straight line.

Spiral bevel gears 

• Spiral bevel gears are used to connect two intersecting shafts.
• Spiral bevel gears have teeth inclined at an angle of the face of the bevel.
• Spiral gears have a spiral angle of 35° usually and the pressure angle varies from 14.5° to 20°.
• Spiral gears offer the following advantages
  • There is a gradual contact between mating teeth therefore there is a smooth and quieter operation.
  • It has more load-carrying capacity because more teeth are in contact at a time and there is a greater arc of contact.
  • It permits higher operational speeds.
  • The spiral bevel gears if made within one system then only they can be interchangeable otherwise they are interchanged with the sets together.