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Gears Flashcards

0
Q

________________ gears have curved angled teeth that transmit motion between parallel shafts.

A

Helical

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1
Q

Name five types of gear designs.

A 
(4 H's, 2 B's, W, S)
Helical
Herringbone
Hypoid
Double helical
Bevel
Spiral bevel
Worm
Spur
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2
Q

____________ gears have straight cut teeth and transmit motion between parallel shafts.

A

Spur

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3
Q

______ gears have cone shaped shafts and transmit motion between shafts at right angles.

A

Bevel or spiral bevel

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4
Q

Helical gears are not preferred to spur gears because they create_______.

A

Thrust

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5
Q

Name the main advantage that double helical (or herringbone) gears have over single helical gears.

A

They eliminate thrust load.

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6
Q

In general, worm gears should be lubricated with oils of ______ viscosity than spur and helical gears. Why?

A

Higher viscosity

A worm gear set has a greater degree of sliding motion.

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7
Q

Name the type of gear that is able to product the largest decrease in speed and the largest increase in torque.

A

Worm gear

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8
Q

What type of gear typically uses bronze as its material?

A

Worm gears (It is actually the gear that is driven by the worm)

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9
Q

What are four functions of gears?

A

Transmit power
Change direction
Change speed
Change torque

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10
Q

Name five gear failure modes.

A

Tooth breakage, surface fatigue ( spalling ), wear and scoring ( galling ), plastic flow ( deformation ), Also, wiping, scuffing, abrasive wear, overload, Hertzian fatigue, brittle fracture, ductile fracture, rolling, bruising, peening, pitting, scratching, cutting gouging, denting, seizing, flacking, feather edging, brinelling, rippling, fish scaling, ridging, tip-to-root interference, adhesion, corrosion, fretting, cavitation, electrical discharge damage, polishing, burnishing, welding, smearing.

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11
Q

What are three factors (or conditions) that affect gear life?

A 
(LETS) 
Load
Environment
Temperature
Speed
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12
Q

What destructive forces lead to plastic flow in gears?

A

Heavy loads and impact loading

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13
Q

What generally causes gear tooth breakage due to fatigue?

A

Many repetitions of bending stresses

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14
Q

The gear tooth dedendum (below the pitch line) will generally show initial pitting. True or False.

A

True

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15
Q

Name four methods that gear manufacturers use to improve surface durability (decrease pitting).

A

Increase hardness
increase face width
Increase pinion pitch diameter
Improve geometry

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16
Q

Name two immediate effects of overfilling a gearbox.

A

Heat
Foam
The fluid may overflow

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17
Q

If you wanted to use only two gear lubricants for an entire plant, what two would you pick and where would they be used?

A

Synthetic EP 460 for heavily loaded, slow speed and worm gears, Synthetic EP 220 for higher speed, lighter loads, parallel shafts

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18
Q

What type of lubricant should be used in a gear box that contains a hypoid gear set?

A

API GL-5 extreme pressure gear oil

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19
Q

Name eight gear oil additives.

A

(FORCE COPS FVI)
Friction Modifiers Compounding Foam inhibitor
Oxidation Inhibitors Oiliness or Polar VI Improvers
Rust Inhibitors Pour paint depressant
Corrosion Inhibitors Solid – Graphite Moly
Extreme Pressure

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20
Q

Why are EP additives not particularly effective with steel in contact with metals such as brass, bronze, babbitt, or aluminum?

A

Contact of a ferrous and non-ferrous metal may not generate temperatures high enough to activate the EP additive.
EP additives may be corrosive to yellow metals at high temperature.
Sliding motion is better lubricated with a PAO of fatty material.

21
Q

Name three types of open gear lubricants.

A

Asphaltic
Soap base
Solvent cutback
Soap base with tackifiers and solid fillers such as moly and/or graphite.

22
Q

What are some of the effects of using gear oil whose viscosity is too low?

A

Increase in noise
Vibration
Temperature
Wear

23
Q

What form of scoring on gears is worse galling or scuffing?

A

Galling

Many tribologists relate galling and scuffing as the same.

24
Q

Name three functions that gears are designed to perform?

A

Reduce speed Increase speed
Transmit power Decrease torque
Increase torque Change direction

25
Q

Name five sets of gears?

A 
Spur                           Internal spur and Pinion 
Rack and Pinion        Helical
Double Helical           Cycloid disk
Straight Bevel            Spiral Bevel 
Hypoid                       Worm
26
Q

Name four sets of gear reducers?

A

Parallel shaft reducer Worm
Right angle Cyclo Drive
Planetary Rack and Pinion

27
Q

In what part of the gear tooth do most failures occur?

A

In the root of the contact side.

28
Q

What type of material would generally be used for a low speed gear?

A

Cast iron

29
Q

What type of material would generally be used for a high speed gear?

A

Steel

30
Q

Name five methods used to apply gear lubricants?

A 
Splash/Idler Immersion
Automatic Spray 
Hand Applied 
Force feed 
Pressure system 
Gravity
31
Q

Name four failure modes found in gear sets?

A

Wear
Surface fatigue
Plastic Flow
Breakage

32
Q

Name five types of typical wear found in gear sets?

A 
Abrasive 
Corrosive 
Polishing 
Frosting 
Scoring
33
Q

Generally, what failure mode has the highest percentage in gear sets?

A

Heat & Lubrication (50 % each)

34
Q

What destructive forces lead to plastic flow in gears?

A

Heavy loads and impact loading

35
Q

Generally, would you recommend oil that is one viscosity grade too high or one viscosity grade too light?

A

One Higher

36
Q

List advantages and disadvantages of hypoid gears.

A

Advantages: Greater load capacity than straight bevel gears, high reduction ration (100:1), supporting shafts can cross, eliminates high hump for rear wheel drive cars.
Disadvantages: Lower efficiency, less speed than spiral.

37
Q

What are advantages and disadvantages of worm gears?

A

Advantages – high shock load, lower cost, high availability, right angle drives, high turn down ratio, smooth and quiet.
Disadvantages – low efficiency, high price per HP, and high thrust.

38
Q

What oils are commonly recommended for worm gear sets?

A

High viscosity (AGMA 7, ISO 460) compounded oil with fatty acids/oils

39
Q

What three advantages to helical gears have over spur gears?

A

Helical gears can take higher loads and speeds, and are quieter in operation.

40
Q

What are three main configurations of spur gears?

A

External
Internal
Rack and pinion.

41
Q

___________ ___________ are often preferred to spur gears because they can operate at high speeds and loads.

A

Helical gear

42
Q

The smallest of a pair of gear drives is often called a _________ gear, and it generally has the _________ number of teeth.

A

Pinion

smallest

43
Q

____________ ________________ is the ability of a gear tooth to withstand repeated loading.

A

Beam strength and hertzian strength

44
Q

Under normal operations, AGMA recommends that a lubricant be changed after what time period?

A

2500 hours or six months, whichever comes first

45
Q

Name three types of gear sets that transmit power at right angles.

A

Worm
Bevels
Spiral bevel
Hypoid.

46
Q

Name two types of gear failures that are not caused by a lubricant problem or that cannot be corrected by a lubricant.

A

Tooth breakage
Overload
Electrical discharge damage.

47
Q

_____________ gears are used to transmit power and motion between shafts which are at right angles to each other but offset.

A

Hypoid

48
Q

____________ and ______________ gears convert rotary motion into linear motion.

A

Rack and pinion

49
Q

Because of ____________ motion, worm gears are often made of _________ ___ ________ and __________ oils are called upon to lubricate them.

A

Sliding
Bronze and brass
Compounded

50
Q

What is the formula for efficiency of a worm gear reducer?

A

Efficiency = 100 - 1⁄2 gear ratio

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