Alb Mod Gearing Fundamentals

Question 1

Gears that are exposed to the outside environment are called:

Answer 1

Open gear drives

Note: used on light duty applications, or where sealing the gears is impractical or impossible

Question 2

With an open gear drive system, gear wear is:

Answer 2

more excessive

Question 3

Gear drives contained within a gearbox with a lubrication supply are:

Answer 3

Enclosed gear drives

Note: Have a long working life

Question 4

____ are matched pairs of gears, manufactured together intended to mate with each other.

Answer 4

Gear sets

Question 5

When two or more gears mesh or work together, they are called a:

Answer 5

Gear train

Question 6

Between a pair of gears, the smaller gear with fewer teeth is referred to as:

Answer 6

pinion

Question 7

With bevel and hypoid gear sets, the smaller gear is called the pinion and the larger gear is called the:

Answer 7

Crown or Ring gear

Question 8

____ is when the input speed of the gearbox is the same as the output speed

Answer 8

direct drive

Question 9

A gear train with a slower output speed than input speed is called a

Answer 9

Speed reducer

Question 10

a gear train with a faster output speed than input speed is called a

Answer 10

Speed increaser

Question 11

When a speed reduction occurs, it results in a mechanical advantage, which is an increase in

Answer 11

torque

Question 12

A ____ has a bearing support on only one side

Answer 12

overhung gear or load

Note: Also known as cantalever

Question 13

The general practice with overhung gears is to keep:

Answer 13

overhung gears very close to the bearing support

Question 14

______ gears are mounted between two bearings

Answer 14

straddle mounted

Question 15

____ gears have teeth on the inside diameter of the gear

Answer 15

Internal

Question 16

____ gear trains have three or more shaft and four or more gears

Answer 16

Compound

Question 17

The final ratio of a compound gear train is equal to all the ratios:

Answer 17

multiplied

Question 18

___ is when the gear or shaft is allowed to move axially

Answer 18

end play

Question 19

____ a bearing in a gearbox id done by giving a bearing less than zero axial clearance

Answer 19

Preloading

Question 20

Gear wear can be caused by: (4)

Answer 20

• Lack of lubrication
• Abrasives
• Incorrect tooth contact
• Heavy loads

Question 21

A ____ exists when one gear or shaft is allowed to move axially to its best position

Answer 21

floating gear or shaft

Question 22

Gears that have a helix angle can be either:

Answer 22

Right or left handed

Question 23

In worm and worm wheel gearboxes, the worm is:

Answer 23

smaller gear that looks like a screw thread

Question 24

The ___ is the side in contact with the other gear teeth while torque is applied. The other side is called the coast side

Answer 24

drive side

Question 25

The ____ is the radial distance from the pitch circle to the top land of the tooth

Answer 25

addendum

Question 26

the ____ is the radial distance from the pitch circle to the bottom land of the tooth.

Answer 26

dedendum addendum + clearance

Question 27

The ___ is the total height of the whole tooth, addendum + dedendum

Answer 27

Whole depth

Question 28

___ is the depth that the gear tooth extends toward the root of the mating tooth while in full mesh

Answer 28

Working depth

Question 29

___ is the space between the bottom land of one tooth and the top land of the meshing gear

Answer 29

Clearance

Question 30

The ____ is the maximum diameter at the top land of the gear teeth

Answer 30

Outside gear diameter

Question 31

____ is the distance from the center of one tooth to the center of the next tooth at the pitch circle

Answer 31

Circular pitch or gear pitch

Question 32

The pitch circle is located, approximately:

Answer 32

in the middle of the gear teeth

Question 33

The ____ of a tooth is the contact part of the tooth on the addendum

Answer 33

Face

Question 34

____ is the contact part of the tooth below the pitch circle including fillet

Answer 34

tooth flank

Question 35

____ is the distance from one side of the tooth to the opposite side

Answer 35

face width

Question 36

____ is the distance of the gear tooth at the pitch circle

Answer 36

chordal thickness Indicates tooth strength

Question 37

Crowning a gear tooth is cutting a slight curve on the face of the tooth from side to side. The purpose is to:

Answer 37

Prevent highly concentrated loads on the ends or edges of the gear teeth that could cause the teeth to fracture

Question 38

The ____ is the angle between the line of action and a line tangent to the pitch circles

Answer 38

Pressure angle

Question 39

The angle of a tooth from the shaft axis is the:

Answer 39

helix angle

Question 40

Helix angles can be right or left handed. They lead to smoother tooth action, but have: (2)

Answer 40

- More sliding friction | - Greater axial thrust

Question 41

A ___ is the term that describes the number of thread starts on a worm

Answer 41

start

Question 42

The more starts a worm has, the ____ the worm wheel advances per turn

Answer 42

Faster

Question 43

The face of the tooth on many gears has a radius across the flank and the face of the tooth. This is referred to as an:

Answer 43

Involute profile. Note: Makes meshing of gears quieter and smoother

Question 44

___ is the clearance between gears at the pitch line. Half is cut into each gear.

Answer 44

Backlash

Question 45

____ is the ratio between the number of teeth on a gear and the pitch diameter. Indicates tooth size.

Answer 45

Diametral pitch

Question 46

When reading diametral pitch, the smaller the number, the ___ the tooth size

Answer 46

larger

Question 47

lack of blacklash, incorrect center distance, gear center out of tolerance, bent shafts and thermal expansion can all cause:

Answer 47

Binding

Question 48

The ____ is the angle of the gear tooth

Answer 48

pressure angle

Question 49

The two most common pressure angles are 14.5° and 20°. Which one is stronger?

Answer 49

20°. Tooth is wider at the base

Question 50

If a gear set has: - Same diametral pitch - same pressure angle - correct hand of gear - shafts in correct position - same helix angle The gears will have proper:

Answer 50

Mesh

Question 51

Gear teeth can have one of two profiles:

Answer 51

Involute or straight

Question 52

An involute profile has a ____ on the face of the gear teeth

Answer 52

slight curve

Question 53

Straight cut teeth are:

Answer 53

Very noisy Note: Also not suitable for high speed or high power applications

Question 54

When an even number of gears are in mesh, the last gear rotates ___ the drive gear

Answer 54

opposite

Question 55

An __________ has both gears moving in the same direction

Answer 55

Internal gear set

Question 56

____ gears are between the drive and driven gear. they have no effect on the gear ratio, but can change the rotation, and connect gears with a greater center to center distance.

Answer 56

Idler gears

Question 57

If a gearbox is a speed increaser, ratios are numberically:

Answer 57

Less than one. 0.50:1, often called overdrives

Question 58

When measuring the torque on a gear, the effective lever length is equal to the:

Answer 58

Radius of the gear

Question 59

What are the three basic positions used to properly mesh gears? (3)

Answer 59

- Parallel - Intersecting - Crossing over at 90°

Question 60

These gears were one of the first developed. Teeth are cut parallel to the shaft axis. Only suitable for shafts that are parallel. No axial thrust, unless misaligned. Easy to manufacture. Sliding and rolling action, but the power transfer happens over a rolling action.

Answer 60

Spur gear, Note: Can be used in 3 arrangements, internal, external and rack and pinion.

Question 61

These gears have their teeth cut at an angle to the shafts axis. They are stronger and have more teeth in contact than a spur gear. Can be used in a single or double setup, to help eliminate thrust loads. When used in parallel, opposite hand helix angles are used. When crossing over at 90, same hands are used.

Answer 61

Helical gears Most common helix angles are 7 to 23°. Greater the angle, more teeth are in contact, more thrust

Question 62

These gears are similar to double cut helical gears, except the teeth form a point in the center of the gear. Cancels out thrust loads. High speed heavy load applications.

Answer 62

Herringbone gears

Question 63

These gears are used on shafts that have intersecting axis. Most commonly cut at a 90° angle, but can intersect at other angles. Develop both axial and radial loads. Can be straddle mounted or overhung. Teeth can be straight or curved.

Answer 63

Bevel gears.

Question 64

These are bevel gears, but have a 1:1 ratio.

Answer 64

Mitre gear

Question 65

This is the simplest bevel gear, teeth are straight but tapered to compensate for the smaller inside tooth diameter. Noisy and rough, do not have a high torque capacity

Answer 65

Straight bevel gears

Question 66

These bevel gears have curved teeth that are angular to the shaft axis. Stronger, have a smoother transfer of power, more teeth in contact. Manufactured in pairs. Gears must be in opposite hand. Generate a thrust load

Answer 66

Spiral bevel gears

Question 67

These bevel gears have teeth cut similar to straight bevel gears, but the teeth are curved. Teeth do not cut at an angle. Are smoother and quieter than straight cut. Does not generate a thrust load.

Answer 67

Zerol bevel gears

Question 68

When gears are too close together, clearance is insufficient, gears are noisy and will bind and wear. If there is excessive clearance:

Answer 68

Cannot transfer rated load, may be noisy