Gears Flashcards
What do gears do?
Transmit torque through positive engagement of teeth
Advantage of gears?
No slippage
What is open gear?
No case or a case taken apart
What is closed gearing?
Gearing in a case
Five designs of gears?
Spur, helical, bevel, hypoid, worm.
How do you know it’s a spur gear?
Straight cut teeth. Moderate speeds
Disadvantage of spur gears?
Noisy and high wear at high speed.
No shock or vibration.
Advantage of spur gear?
No thrust loading
Low cost
Low maintenance
With no idler and with idler what way do two spur gears turn?
No idler - opposite
Idler - same
How to find ratio of two gears?
Big gear / small gear
What is the smaller gear called?
Pinion
Advantage of helical gars?
More load, smoother quieter operation, less vibration and higher speeds
Disadvantage of helical gears?
Have to have thrust load bearings.
Advantage of double helical gears?
No thrust loading.
Good for shock and vibration.
Smooth operation.
Hugh speed and ratio in single stage.
Advantage of herringbone gears?
Good for shock and vibration.
High single reduction.
More torque less speed then double helical gears.
When do you use internal gears?
Where space is an issue.
What direction do internal gears rotate?
Same direction unless has an intermediate gear then opposite direction.
Parts of planetary system gears?
Pinion - suns gear
Idler - planet gear
Ring - ring gear
Advantages of planetary system over internal gears?
More power transfer
What does a gear rack / rack and pinion do?
Convert rotational motion into linear motion.
What is cross axis helical gear used for?
Transmit power at different angles 90 degrees on shaft
Light to moderate load
What are worm gears used for?
Transmit power on a right angle on non intersecting shafts
Advantage of worm gear?
High speed-reduction ratios in a limited space
Shock loads
Quite
Constant output speed free of pulsations
Disadvantage of worm gear?
Lower efficiency then other gear types
Produce a thrust load need bearings
Three types of worm gears?
Cylindrical (lowest torque) (low load)
Single envelope (medium)
Double envelope (most torque) (high load)
Disadvantage of bevel gears?
Thrust loads on both shafts
Four types of bevel gears?
Straight, zerol, spiral, skew.
