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Millwrong > Gears > Flashcards

Gears Flashcards

1
Q

What are the two types of gear drives?

A
  1. open gear drives
  2. enclosed gear drives
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2
Q

Gear trains that are exposed to the outside environment are called:

A

open gear drives

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3
Q

What is usually used to lubricate open drive systems?

A

very thick oil or grease

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4
Q

Which system has more excessive gear wear: an open drive system or an enclosed drive system?

A

open drive

*particulate matter causing additional wear

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5
Q

Gear drives contained within a gearbox with a lubrication supply are _____________.

A

enclosed

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6
Q

What are gear sets?

A

matched pairs of gears manufactured and intended to mate with each other

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7
Q

What 2 types of gears are usually manufactured as gear sets?

A
  1. hypoid
  2. bevel
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8
Q

What can happen if a gear from a gear set is matched with a gear that wasn’t their mate?

A

failure can result

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9
Q

What is a gear train?

A

when two or more gears mesh and work together as a unit

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10
Q

When two gears having different numbers of teeth mesh together, the gear with the fewer teeth is called the ___________ gear.

A

pinion

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11
Q

True or false:

The pinion gear is rarely the drive gear.

A

false;

it is generally the drive gear

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12
Q

In bevel and hypoid gear sets, the smaller gear is called the 1.____________ gear and the larger gear is called the 2.____________ gear.

A
  1. pinion
  2. crown
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13
Q

The crown gear is also called the:

A

ring gear

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14
Q

What is the input gear on a gear train called?

A

drive or driver gear (power in)

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15
Q

What is the output gear on a gear train called?

A

driven gear (power out)

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16
Q

What is a direct drive gearbox system?

A

where the input speed = output speed

*transfer power, no increase or decrease of speed

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17
Q

A gear train with a slower output speed is called a:

A

speed reducer

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18
Q

A gear train with a faster output speed is called a:

A

speed increaser

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19
Q

What happens to the output torque when a speed reduction occurs in a speed reducer?

A

the toque increases due to the mechanical advantage

speed ↓ = torque ↑

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20
Q

What effects the amount of mechanical advantage that’s seen in a speed reducer?

A

the input to output ratio

  • the larger the ratio (greater the speed reduction), the greater the mechanical advantage
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21
Q

What is an overhung gear?

A

A gear with support only on one side

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22
Q

What 2 kinds of gears are overhung loads common on?

A
  1. Bevel
  2. Hypoid
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23
Q

General practice is to keep overhung gears very close to the bearing. Why is this?

A

For support, as they tend to have more shaft deflection

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24
Q

What is a straddle mount gear?

A

A gear mounted between two bearings

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25
Q

What are internal teeth gears?

A

Gears that have the gear teeth on the inside diameter of the gear

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26
Q

What are 2 advantages of internal gears?

A
  1. Operate more smoothly than external gears
  2. More tooth contact vs. External tooth gears
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27
Q

Compound gear trains have 1._________ or more shafts and 2._________ or more gears.

A
  1. three
  2. four
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28
Q

In any gear train with more than one gear set, what does the final ratio at the output shaft equal?

A

all the ratios through the gear train multiplied together

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29
Q

If a gear train has a reduction of 4:1 on the first set, a ration of 3:1 reduction on the second set, and a reduction of 5:1 of the third set, what would the final ratio be?

A

4 x 3 x 5 = 60:1

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30
Q

What is end play on a gearbox?

A

when a gear or shaft is allowed to move axially

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31
Q

_______________ a bearing in a gearbox is accomplished by giving the bearing less than zero axially clearance.

A

Preloading

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32
Q

In a gearbox, what is the axis of rotation?

A

the centreline around which a gear or part moves

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33
Q

What are the 4 main reasons for gear wear?

A
  1. lack of lubrication
  2. abrasives in the gear train
  3. incorrect tooth contact
  4. extended heavy loads
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34
Q

True or false:

An increase in backlash can be an indication of gear wear.

A

true

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35
Q

What is a floating gear or shaft?

A

where one gear or shaft is allowed to move axially into a self-centred position

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36
Q

On helix gears, if the teeth point to the 1._________, as viewed from the shaft axis then the gear is right-hand gear and if the teeth point to the 2.__________ it is left-hand gear.

A
  1. right
  2. left
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37
Q

In a worm and worm wheel gear set, the ___________ is the smaller gear that looks like a screw thread.

A

worm

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38
Q

The __________ side of gear teeth is the side in contact with the other gear teeth while torque is applied to the gear train.

A

drive

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39
Q

What is the opposite side of the drive side on a gear?

A

the coast side

  • side where no torque is applied during normal operation
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40
Q

What is the addendum of a gear?

A

the top half of the gear tooth

  • the radial distance from the pitch circle diameter to the top land of the tooth
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41
Q

What is the dedendum of a gear?

A

the bottom half of the gear tooth included the clearance

  • radial distance from the pitch circle to the bottom land of the tooth
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42
Q

What is the whole depth of a gear tooth?

A

total height of the tooth

  • addendum + dedendum = total depth
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43
Q

What is working depth of a gear tooth?

A

the depth the gear extends toward the root of the mating tooth when both gears are in full mesh

  • working depth = addendum + dedendum - clearance
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44
Q

When it comes to a gear tooth, what is clearance?

A

the space between the bottom land of one gear and the top land of the meshing gear

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45
Q

What 3 things do gear tooth clearance allow for?

A
  1. lubricant
  2. thermal expansion
  3. gear runout
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46
Q

What 3 things can happen if there is not enough clearance in a gear tooth?

A
  1. binding
  2. increased friction
  3. loss of power
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47
Q

What is the outside gear diameter of a gear?

A

the diameter of the gear when measured from the top land of the gear teeth

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48
Q

What is the circular pitch of a gear?

A

the distance form the centre of one tooth to the centre of the next tooth at the pitch circle diameter

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49
Q

What is circular pitch also called?

A

gear pitch

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50
Q

What is pitch circle?

A

the diameter of the gear approximately in the middle of the gear teeth

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51
Q

Pitch circle is also known as:

A

pitch diameter

  • most often known as pitch cirlce diameter (PCD)
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52
Q

On a gear, what is the face of the tooth?

A

the contact part of the tooth on the addendum or top half of the tooth

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53
Q

What is the tooth flank of a gear?

A

the contact part of the tooth below the pitch circle, including the fillet

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54
Q

What is the face width of a gear?

A

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

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55
Q

What is the chordal thickness of a gear tooth?

A

the thickness of the gear tooth at the pitch circle diameter

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56
Q

What is chordal thickness of a gear tooth indicative of?

A

tooth strength

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57
Q

____________ a gear tooth is cutting a slight curve on the face of the tooth from side to side.

A

Crowning

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58
Q

What is the point of crowning a gear tooth?

A

to reduce loads on the ends or edges of the gear tooth

  • these are the loads that cause the teeth to fracture
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59
Q

What is the line of action of a gear tooth?

A

the points of contact as the gear turns

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60
Q

What is the helix angle of a gear tooth?

A

the angle of the gear tooth relative to the axis of the gear

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61
Q

On a worm gear, what is a start?

A

the number of thread starts on the worm gear

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62
Q

What effect does the number of starts have on the worm wheel?

A

the more starts, the faster the worm wheel advances in one turn of the worm

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63
Q

What is the involute profile of a gear tooth?

A

The radius on a gear tooth (across both the flank and the face) that makes the meshing of gears smoother

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64
Q

What indicates the number of teeth on a worm gear?

A

The number of starts

Number of starts = number of teeth

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65
Q

Where does the rolling action of gears meshing take place on the gear tooth?

A

On the involute profile of the flank and face of the gear tooth at the pitch circle

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66
Q

What is the contact pattern of a gear tooth?

A

the pattern on the tooth that are in contact when the gears are meshed and when checked gives an indication of relative gear position

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67
Q

What is the diametral pitch of a gear?

A

the ratio between the number of teeth on a gear and the pitch diameter

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68
Q

What formula is used to calculate the diametral pitch?

A

DP = # teeth ÷ PCD

DP = diametral pitch
# teeth = number of teeth on the gear
PCD = pitch circle diameter

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69
Q

If the diametral pitch of a gear is small, the teeth of the gear are physically ___________.

A

large

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70
Q

What is backlash as it pertains to a gear?

A

the clearance between the gear teeth at the pitch line approximately half way up the tooth face

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71
Q

What formula is used to calculate average backlash of a gear?

A

average backlash = 0.40” ÷ DP

DP = diametral pitch

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72
Q

What are the 3 benefits that backlash in a gear allows?

A
  1. keeps teeth from binding
  2. allows for thermal expansion
  3. allows for the lubricating film
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73
Q

What are the 5 common causes of binding in a gearbox?

A
  1. lack of backlash or clearance
  2. incorrect centre distance
  3. gear centre out of tolerance
  4. bent shafts or shaft deflection under load
  5. thermal expansion
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74
Q

What are the 2 most common gear tooth pressure angles?

A
  1. 14.5º
  2. 20º
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75
Q

Which gear tooth pressure angle is stronger?

A

20º

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76
Q

As gears mesh, the action between the teeth is 1.____________ until both teeth are at contact at the pitch line, at which time the action changes to a 2.___________ action until the teeth begin to pull out of mesh and pull apart.

A
  1. sliding
  2. rolling
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77
Q

When gears mesh, during the initial stages of contact, the 1.______________ of the tooth on one gear contacts the 2.______________ of the tooth on the opposite gear.

A
  1. dedendum
  2. addendum
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78
Q

What 5 things must gears have to mesh properly?

A
  1. same DP
  2. same pressure angle
  3. correct hand
  4. same helix angle
  5. proper shaft position
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79
Q

What are the 2 gear profiles?

A
  1. involute
  2. straight
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80
Q

When an even number of gears mesh with each other, the last gear rotates in the _________________ (same/opposite) direction as the first one.

A

opposite

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81
Q

When an odd number of gears mesh with each other, the last gear rotates in the __________________ (same/opposite) direction as the first one.

A

same

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82
Q

What are idler gears?

A

gears between the drive and driven gear

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83
Q

What effect do idler gears have on the gear ratio of the gears that they mesh with?

A

no effect on the ratio

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84
Q

What are 3 functions of idler gears?

A
  1. change the direction rotation (or keep it the same depending requirements)
  2. connect two gears together (close gaps)
  3. function as moveable gears for setting backlash and mesh
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85
Q

What type of gearbox is an overdrive gearbox?

A

a speed increaser

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86
Q

How can the overall gear ratio be calculated if only the individual gear ratios inside a gearbox are known?

A

by multiplying all of the ratios together

  • always follow the input, as this will let you know if its a speed reducer or increaser
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87
Q

What formula can be used to find the mechanical advantage of a gearbox?

A

MA = N(out) ÷ N(in)

MA = mechanical advantage
N(out) = # of teeth on the output gear
N(in) = # of teeth on the input gear

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88
Q

What are the 3 basic shaft positions that allow gears to mesh properly?

A
  1. parallel
  2. intersecting
  3. crossover at 90º
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89
Q

What must the hand be on helical gears that are mounted on parallel shafts?

A

they must have the opposite hand

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90
Q

What two types of gears can be mounted on intersecting shafts at 90º?

A
  1. bevel (straight, sprial, Zerol)
  2. mitre
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91
Q

What must the hand be on helical gears that are mounted in a crossing over at 90º shaft arrangement?

A

the must have the same hand

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92
Q

This type of gear is cut with teeth parallel to the shaft axis and develop only radial torque and no axial thrust (unless misaligned).

A

spur gears

93
Q

What are the 3 types of spur gears?

A
  1. external
  2. internal
  3. rack and pinion
94
Q

This type of spur gear arrangement converts rotary motion into linear motion.

A

rack and pinion gear arrangement

95
Q

What is it called when spur gears are cut on to a linear surface?

A

a rack

96
Q

When spur gears are mounted in the gearbox housing, the correct centre-to-centre distance between the gears is half the sum of the:

A

pitch circle diameters of the two gears

centre-to-centre = (PCDA + PCDB) ÷ 2

97
Q

True or fasle:

The torque capability of spur gears is limited to one tooth in full contact at at time.

A

true

98
Q

What are the two disadvantages of helical gears when compared to spur gears?

A
  1. cost
  2. axial thrust
  • friction and the required lubricants can also be considered a disadvantage
99
Q

Why is it important to select the correct lubricant for gearboxes that contain helical gears?

A

the increased sling action increases the pressure applied to the lubricant

  • EP rated lubricant is a must
100
Q

What determines the direction of axial thrust of a helical gear?

A

the hand and the rotation of the gears

101
Q

How can the axial thrust direction of a helical gear be determined if the rotation is known?

A

using the Right Hand and Left hand rules

  • which rule to use depends on the drive gear; a right hand drive = RH rule, a left hand drive = LH rule
  • to use the rule, place your right hand (or left, depending on the drive) with the fingers orientated in the direction of rotation. The thumb will indicate the direction of axial thrust
102
Q

What advantage does increasing the helix angle have on the gears?

A

increased strength/greater torque due to more teeth being in contact at the same time

103
Q

What is the main advantage of using double helical gears?

A

the double helical cancels out the axial thrust normally produced

104
Q

Helical gears can have pressure angles from 1.______º to 2.______º, with 3._______º being the most common for industrial gears.

A
  1. 7º
  2. 23º
  3. 20º
105
Q

This type of gear is similar to double-cut helical gears, but the point forms at the centre of the gear.

A

herringbone gears

106
Q

Most bevel gears develop both axial and radial loads. What is the exception to this?

A

Zerol gears;

They do not develop axial loads

107
Q

What can happen to overhung gears that are subject to shock loads?

A

the shaft deflects, causing the gear teeth to move out of proper mesh

108
Q

What are the 3 types of bevel gear tooth geometry?

A
  1. straight tooth
  2. spiral tooth
  3. Zerol tooth
109
Q

What is a mitre gear?

A

bevel gears that intersect at 90º with both gears having the same number of teeth

110
Q

For spiral bevel gears to mesh, the gears must be of the __________ (same/opposite) hands.

A

opposite

111
Q

This type of gear forms a drive between two shafts that cross over and are also at 90º to each other.

A

hypoid gears

112
Q

This type of gear will whine or howl is they are not set up correctly.

A

hypoid gears

113
Q

Why are hypoid gears smoother and quieter than bevel gears?

A

they have more sliding action

114
Q

This type of gear set is used where a high ratio reduction is required in relatively little space.

A

worm gear set

115
Q

What kind of shaft positions are worm gear sets found in?

A

crossover at 90º

116
Q

On worm gear sets, the worm and the worm wheel always have the _______________ (opposite/same) hand.

A

same

117
Q

The worm on a worm gear set is always the ________________ (input/output).

A

input

118
Q

If the worm on a worm gear set has only a few starts, it tends to be self-locking. What does that mean?

A

the drive will not rotate backwards against the worm when power is removed

  • useful for backstop applications
119
Q

What types of bearings would be found in a worm gear set?

A

tapered roller bearing

120
Q

Which type of gear set creates the most friction?

A

worm and worm wheel

121
Q

This type of gear set is often housed in a gearbox that has fins on it.

A

worm and worm wheel

  • the fins are used as heat sinks, due to the excessive heat generated by the gears
122
Q

What 6 things affect the efficiency of a worm gearbox?

A
  1. gear ratio
  2. input speed
  3. lead angle
  4. gear material
  5. gear design
  6. amount of output torque
123
Q

What affect does increasing the ratio of a worm gearbox have?

A

ratio ↑ = friction ↑ = heat ↑= efficiency ↓

124
Q

What is the worm pitch of worm gear set?

A

the distance from one tooth to the next on the worm

  • think thread pitch
125
Q

What is the worm lead on a worm gear set?

A

the distance by which one tooth on the worm advances in one turn

126
Q

What formula is used to calculate the lead of a worm gear?

A

pitch x number of starts = lead

127
Q

What is the number of starts on a worm gear?

A

the number of thread beginnings machined into the worm

128
Q

How is the ratio of a worm gear set determined?

A

ratio = number of worm wheel teeth ÷ number of starts on the worm

129
Q

In a worm gearbox, the worm can be shaped two ways: __________________ is shaped like a cylinder and _________________ is shaped like an hourglass.

A

non-throated = cylinder
throated = hourglass

130
Q

True or false:

The worm wheel on a worm gearbox can be both throated and non-throated.

A

true

131
Q

When a worm wheel is _________________, the tops of the wheel will have flat tops.

A

non-throated

132
Q

When a worm wheel is ________________, the tops of the wheel will be concave in the middle.

A

throated

133
Q

What effect does whether a worm gear set is throated or non-throated have on the gearbox?

A

it determines the amount of torque the gears can handle

  • power transfer
134
Q

In a _______________ worm gear set, both the worm and worm gear are non-throated.

A

non-throated

135
Q

In a _______________ worm gear set, either the worm wheel teeth or the worm is throated.

A

single-throated

  • most common is throated worm wheel and non-throated worm
136
Q

In a ______________ worm gear set, both the worm and worm wheel are throated.

A

double-throated

137
Q

Which type of throat/non-throated worm gear set configuration give the maximum gear tooth contact?

A

double-throated

138
Q
  1. To achieve the maximum power and life of a worm gear set, the worm wheel contact should be toward the ______________ (entering/leaving) side of the worm wheel.
  2. Why is this?
A
  1. leaving
  2. this is to allow oil to into the entering side of the gear
139
Q

What are 4 heat treatments used on steel gears?

A
  1. hardened and tempered
  2. flame or induction hardened
  3. carburized and case hardened
  4. nitrided
140
Q

What kind of application are brass gears used for?

A

light load or slow turning applications

141
Q

What type of gears are insulators and protect against electrical current?

A

non-metallic gears

142
Q

What are 4 advantages of non-metallic gears?

A
  1. cost savings
  2. quieter operation
  3. run with limited lubrication, if any (self-lubricating)
  4. absorbs vibration
143
Q

What type of metallic gear is preferred for meshing with non-metallic gears?

A

cast iron

144
Q

What are 4 common types of material used in non-metallic gears?

A
  1. nylon
  2. Teflon
  3. acetal resin
  4. fabric impregnated resins
145
Q

What are the 3 parts of a planetary gear system?

A
  1. sun gear
  2. carrier with mounted planet gears
  3. ring gear
146
Q

In a planetary gear system, the __________ gear meshes with the planetary pinion gears, which in turn meshes with the ring gear.

A

sun

147
Q

True or false:

In a planetary gear set, the gears are always in mesh.

A

true

148
Q

What is the reaction member of a planetary gear set?

A

the member of the gear set that is being held in place

  • can be any of the parts (sun, planetary, ring)
149
Q

What happens if two of the members of a planetary gear set are held?

A

the gear system becomes a direct drive system

150
Q

What type of final output would be seen if none of the members of a planetary gear system were held?

A

it would be a neutral system

151
Q

True or false:

Planetary gear sets can be either spur or helical designed gears.

A

true

152
Q

How can a planetary gear system be made to handle more torque?

A

by adding more planetary pinion gears

153
Q

A single reduction gearbox has 1._______ shafts and 2._______ gears.

A
  1. two
  2. two
154
Q

A double or multiple reduction speed reducer has at least 1.__________ shafts and 2.___________ gears.

A
  1. three
  2. four
155
Q

_______________ reducers have the input shaft and output shaft mounted on different planes.

A

offset

156
Q

______________ reducers have the input and output shafts on the same plane.

A

concentric

157
Q

What is the active flank of a gear tooth?

A

the drive side

158
Q

It is common to have the mesh pattern on a unidirectional worm gear set favouring the leaving side of a worm wheel. Why is this?

A

to provide clearance on the entry side for lubricant to enter and form a fluid film

  • on a bidirectional gearbox, it would be in the middle
159
Q

What are 4 ways to check for mesh patterns in a gearbox?

A
  1. Prussian blue
  2. Venetian red
  3. black light
  4. pencil lead
160
Q

The mesh patterns of gears should be checked and recorded in a minimum of _______ locations on each gear.

A

4

161
Q

How are the mesh and backlash of spiral bevel gears adjusted?

A

by shimming the crown or pinion gear

162
Q

How is backlash measured in worm and worm wheel reducers?

A

by restricting the rotation of one gear (usually the pinion) and measuring the rotational movement of the other gear at its pitch circle diameter

163
Q

What are 3 common ways of checking backlash?

A
  1. dial indicator
  2. lead wire
  3. feeler gauges
164
Q

What must be done to get an accurate measurement of backlash using the lead wire method?

A

the wire must be measured in two locations, as the wire has been squeezed between the mating teeth

165
Q

What is a good practice when installing a new gearbox onto a sole plate?

A

to place 1/8” shims below the gearbox to allow for downward movement during alignment

166
Q

What issues can soft foot cause in a gearbox?

A

distortion of the internal parts leading to binding, heating, and eventual lubrication and bearing failure

167
Q

What devices must be used when a gearbox is mounted on the output shaft?

A

an anti-rotational device, such as a flange mount or torque arm

168
Q

Where should shaft-mounted reducers be mounted to work best and last the longest?

A

as close as possible to a support bearing

169
Q

What mounting precautions must be taken when using a tie rod (torque arm) as an anti-rotation device on a shaft mounted reducer?

A

it must be mounted in a position that forms a right angle between the tie rod and a line running from the output shaft to the point of attachment

170
Q

When V belts are used to drive a shaft mounted reducer, how must the V belts be orientated?

A

at a 90º angle between output and centre of V-belt drive

171
Q

This type of direct mechanical drive uses the motor shaft and the input shaft as one complete unit.

A

gear motor units

172
Q

Why are most shaft-mounted reducers V-belt driven?

A

cost effectiveness

173
Q

When dealing with a high-ratio planetary drive, what is reverse torque lockup?

A

a condition where the gears bind up in the reverse direction and stop any reverse motion

174
Q

What precautions must be taken when working on planetary gear drives?

A

they can act as backstops, so the driven unit can supply energy back into the gearbox

175
Q

What type of fasteners should be used when assembling a gearbox after overhaul?

A

New grade 8 fasteners with star washers or lock wire

176
Q

What can happen to copper tubing in gearboxes?

A

they can work harden due to vibration and pressure pulses

177
Q

Gearbox lubricant, at the minimum, should be changed every 1.____________ service hours or after 2.______ years.

A
  1. 20,000 hours
  2. 4 years
178
Q

Bearings in gearboxes should be cleaned and packed with fresh grease every __________ service hours.

A

10,000 hours

  • only fill to 1/3 of housing
179
Q

What should be used to remove sharp-edged high spots and burrs on a gear tooth?

A

a tapered oilstone and light oil

  • also called an abrasive file
180
Q

What should be used to finish the surface of a tooth after it’s been cleaned up with an abrasive file?

A

2800 grit aluminum oxide stone

181
Q

How is a residual magnetism check done on a gearbox?

A

with a quality compass

182
Q

True or false:

The finish on the shaft at the seal contact area should be a 10 to 20 micron finish done by a plunge grinder.

A

true

183
Q

What does the gear term backlash refer to?

A

the arc clearance between mounted, mating gears

184
Q

Why would you number a gear in four location with numbers stamped on the side of the gear?

A

to allow backlash and mesh pattern checks over 360º or at four locations to establish gear and shaft integrity

185
Q

Damaged gear teeth must be hand-worked to remove burrs and high spots. What tools can you use to dress damaged teeth?

A

abrasive files

186
Q

What is used for checking for gear teeth cracks?

A

NDT dye penetrant and developer

187
Q

Why is residual magnetism dangerous to rebuilt gearboxes?

A

the magnetism attracts iron particles to wear surfaces

188
Q

Define P.I.V as it pertains to power transmission components.

A

positive infinitely variable

189
Q

True or false:

The turnbuckle on a shaft mounted gearbox can be used as a belt tensioner.

A

true

190
Q

How is the speed varied on a tube drive scoop?

A

By changing the level of fluid in the case

191
Q

Which set of bevel gear sets cross over at 90° and have extensive sliding friction?

A

hypoid gears

192
Q

How can the worm and worm wheel be designed so they have the maximum amount of tooth contact?

A

double-throated

193
Q

If straight bevel gears are used at angles other than 90°, what are they called?

A

angular bevel gears

194
Q

What formula can be used to calculate pitch circle diameter of a gear if the tooth count and diametral pitch of the gear are known?

A

PCD = # teeth ÷ DP

PCD = pitch circle diameter
# teeth = number of teeth on the gear
DP = diametral pitch of the gear

195
Q

What would the final output be on a planetary gear set if none of the planetary members are held while there still being an input?

A

a neutral drive

196
Q

What would the final output be on a planetary gear set if two of the gear members were locked together?

A

a direct drive output

197
Q

How can the output and speed change be determined in a planetary gear set when the held and input members are known?

A
  1. 3 vertical dots labelled from top to bottom R, C, and S (ring, carrier, sun)
  2. ensure that the distance between C and S is double that of R to C
  3. mark the held member with an X
  4. draw a vertical line to the right from the input member
  5. draw a vector starting at the held member and intersecting the end of the horizontal line from the input
  6. draw a line from the output to the vector; this will determine speed increase (longer line than the input line) or decrease (shorter line that input line) as well as direction
  • direction is based off of input line ⟶ if you draw the input line to the right, that is forward. if the resultant vector stays on the right, it is the same direction, if it ends up on the left, it is a reverse direction
198
Q

AGMA suggests that backlash measurements indicate that as diametral pitch increases:

A

backlash increases

The larger the DP, the smaller the DP number

  • average backlash = 0.04” ÷ DP
199
Q

The worm gear set with the most amount of tooth contact pressure is:

A

non-throated

200
Q

Hypoid gear sets utilize a __________ shaft orientation.

A

crossing over

201
Q

The mechanical advantage of a multiple reduction gearbox is equal to:

A

The product of the gear ratios within the gearbox.

202
Q

The more ____________ on the worm gear, the faster it advances the worm wheel.

A

starts

203
Q

True or false:

Most often the end float of shafts within gearboxes must be near zero when measured on a dial indicator.

A

True

204
Q

What are two advantages of a spring-mounted torque arm?

A
  1. Allows for some torsional flexibility (twisting)
  2. Absorbs shocks
205
Q

What type of device is found in gearboxes and is used to remove excess oil off of gears and direct them into passageways that lead to bearings?

A

Oil scrapers

206
Q

What 3 things cause destructive pitting?

A
  1. Contaminated lubricants
  2. Excessive heavy loads
  3. Low speed conditions (lack of lubricant)
207
Q

This type of gear set crosses over and are at 90 degrees, but usually the two gears are not at the same centreline.

A

Hyoid gear sets

208
Q

True or false:

Crowning aids with preventing seizing of gears.

A

True

209
Q

With single helical gears, what bearings must be installed in the gearboxes?

A

Thrust bearings due to the axial torque

210
Q

True or false:

Reversing gearboxes containing single helical gears requires thrust bearings on both ends of the shaft.

A

True

211
Q

This type of bevel gear is stronger than others due to their cross over shaft orientation that allows the pinion gear to be straddle mounted.

A

Hypoid gear

212
Q
  1. Which is the strongest type of bevel gear?
  2. Why is this?
A
  1. The Hypoid gear
  2. Due to the pinion being larger because of their ability to be straddle mounted
213
Q

Which friction action is better for extending the life of a gear: rolling or sliding?

A

Rolling

  • less friction
214
Q

What can effect the rotation of a gear train if the number of gears are known?

A

If all of the gears mesh, or if some of the gears are on the same shaft

  • gears on the same shaft count as one gear, so the total number of meshed gears would be reduced by 1 per gears that share the same shaft
215
Q

What is the most common single-throated worm gear set arrangement?

A

throated worm wheel and non-throated worm

216
Q

What does the contact pattern of meshing gears indicate?

A

the relative gear position

217
Q

What types of loads do Zerol gears not develop: radial or axial?

A

axial;

  • they do not develop axial loads
218
Q

Identify the following gear geometries:

A

A = straight bevel
B = Zerol bevel
C = spiral bevel
D = hypoid

219
Q

What is the shaft arrangement of an opposite hand helical gear set?

A

parallel shafts

220
Q

What is the shaft arrangement of a hypoid gear set?

A

crossing over

221
Q

What is the shaft arrangement of a mitre gear set?

A

intersecting

222
Q

What is the shaft arrangement of a herringbone gear set?

A

parallel

223
Q

What is the shaft arrangement of a worm gear?

A

crossing over

224
Q

What is the shaft arrangement of a spiral bevel gear?

A

intersecting

225
Q

What is the shaft arrangement of a Zerol bevel gear set?

A

intersecting

226
Q

What is the shaft arrangement of a same hand helical gear set?

A

crossing over

227
Q

What is the shaft arrangement of spur gears?

A

parallel

228
Q

What is the shaft arrangement of double helical gears?

A

parallel

229
Q

True or false:

When using Prussian blue to check for gear mesh on a worm and worm wheel gearbox, it is preferable to put the Prussian blue on the worm wheel rather than the worm.

A

True

230
Q

What are 3 common ways to mount gearboxes?

A
  1. Foot mounted (most common)
  2. Flange mounted
  3. Shaft mounted
231
Q

What determines the direction of thrust of a helical gear?

A

the direction of rotation

  • while the helix angle also determines this, the main component will be the direction of rotation

Millwrong (27 decks)

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