401c Gearing Principles

Question 1

Gear teeth may be parallel to one another or they may be tapered, with one large end and one smaller end.
T/F

Answer 1

true

Question 2

A gear tooth can be sub-divided into four (4) distinctive quadrants. Identify the names of each of those quadrants.

Answer 2

• face
• flank
• heel
• toe

Question 3

The gear pitch line is used to divide what gear tooth areas:

Answer 3

face and flank.

Question 4

When two gears are in mesh, a gap is formed between the tip of one gear tooth and the root in the opposite gear. This gap is called the:

Answer 4

clearance.

Question 5

Explain why some angle drive gear sets may need to be timed.

Answer 5

The manufacturer may design the gear set in such a manner that a very distinctive wear pattern will exist between the mating gear teeth during operation. The gears have been lapped in this pattern and need to be timed to continue this specific relationship.

Question 6

Gears may operate together as direct drive assemblies. Identify two (2) other types of gear configurations and explain the type of speed and torques changes that would be expected between the input and output members.

Answer 6

• Reduction. Speed reduction, torque increase.

- Overdrive. Speed increase, torque reduction.

Question 7

If a simple gear set has a gear ratio of 4:1. Explain which member is turning at 4 revolutions.

Answer 7

Drive (input) member is rotating at 4 revolutions.

Question 8

Which of the following gear ratios would be a reduction gear ratio?

a) 0.10:1
b) 1.00:1
c) 10.00:1
d) 1.00:2

Answer 8

c) 10.00:1

Question 9

When installed between a drive and a driven gear, an idler gear affects speed and torque changes between the two gears.
T/F

Answer 9

false; An idler gear causes a driven gear to change direction of rotation.

Question 10

Explain the purpose of an idler gear.

Answer 10

An idler gear is used to change the direction of rotation of the driven gear to the same direction of rotation as the drive gear. This action could make the selection of reverse gear possible.

Question 11

Name, and explain, the tooth design used on two (2) types of external gears.

Answer 11

• Straight cut spur gear. Teeth cut inline with the mounting shaft.
• Helical gear. Teeth cut at an angle to the mounting shaft.
• Double helical gear. Two sets of teeth, each cut at an opposite angle to the mounting shaft.

Question 12

Identify one (1) common gear set where internal gears may be used.

Answer 12

Planetary gear sets.

Question 13

What is another name for a double helical gear?

Answer 13

Herringbone gear.

Question 14

Straight cut spur gears and helical gears both produce axial thrust loads during operation.
T/F

Answer 14

false; Only helical gears produce axial thrust loads.

Question 15

Identify the three (3) main components of a simple planetary gear set.

Answer 15

• internal gear (ring gear)
• planet pinion gears and planet carrier assembly
• sun gear