Gears and Gear Drives

Question 1

What do gears do?

Answer 1

• change direction of motion
• transmit power

Question 2

When a pair of gears mesh they cause…

Answer 2

sliding and rolling actions due to torque and interaction forces

Question 3

Types of Gears (5)

Answer 3

• Spur
• Helical
• Bevel
• Hypoid
• Worm

Question 4

What is unique about Spur Gears?

Answer 4

The cogs are parallel to the shaft axis

Question 5

What kind of load does a spur gear work well with?

Answer 5

Radial

Question 6

What kind of load does a spur gear NOT work well with?

Answer 6

Axial

Question 7

Advantages of Spur Gears (3)

Answer 7

• low cost
• easy to design
• easy to repair

Question 8

Disadvantages of Spur Gears (3)

Answer 8

• bad for thrust loads
• work for moderate speeds
• causes noise at high speeds

Question 9

Diametral Pitch

Answer 9

Ratio of the number of teeth to the pitch diameter

Question 10

In a Gear and Pinion, which one is the gear?

Answer 10

the larger one

Question 11

In a Gear and Pinion, which one is the pinion?

Answer 11

the smaller one

Question 12

What does an idler do?

Answer 12

only in charge of maintaining direction

Question 13

Speed Ratio

Answer 13

Ratio of the number of teeth on the larger to that of the smaller

Question 14

Types of Helical Gears (4)

Answer 14

• Helical
• Double Helical
• Herringbone
• right vs left gear

Question 15

How can you tell whether it’s a right or left gear?

Answer 15

Draw a down arrow and which ever corner its pointed towards is the direction of the gear

Question 16

Helical Gears - Advantage (2)

Answer 16

• Greater loads
• handle radial and axial loads

Question 17

Advantages of Gears (3)

Answer 17

• shafts do not need the be parallel
• can change direction
• good in small spaces

Question 18

For a closed loop gear system, the number of cogs should be

Answer 18

Even

Question 19

Helical Gear - Disadvantage

Answer 19

all vibrations are transmitted from one gear to another (no dampening)

Question 20

Double Helical Gear - Advantage

Answer 20

natural dampening effect

Question 21

Beveled Gear - Advantage

Answer 21

Capable of transmitting power between intersecting shafts

Question 22

Straight tooth beveled gear example

Answer 22

Miter Gear

Question 23

Types of Beveled Gears (4)

Answer 23

• Straight Tooth
• Spiral Bevel
• Zerol Bevel
• Skew Tooth Bevel

Question 24

Difference between Spiral Bevel and Skew Tooth bevel

Answer 24

• Spiral Bevel: angle of 10-36 degrees
• Skew Tooth: angle of 35 to 55 degrees

Question 25

What happens when the helix angle is less than 5 in worm and wheel?

Answer 25

self-locking

Question 26

Worm and Wheel - Advantages (2)

Answer 26

• shock loads (provides constant output)
• high speed ratios (100:1)

Question 27

Worm and Wheel - Disadvantage

Answer 27

sliding is possible (reduces efficiency)

Question 28

Rack and Pinion Gear - _____ motion to _____ motion

Answer 28

Rotary motion to linear motion