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Red Seal Study Prep > Couplings And Clutches > Flashcards

Couplings And Clutches Flashcards

1
Q

When choosing couplings what must you consider?

A

-The amount and type of miss alignment
- how much is likely to occur

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2
Q

Couplings are used to ?

A

Transmit power from a driving source to a driven machine

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3
Q

Clutches are used to ?

A

Engage and disengage the power of two shafts

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4
Q

Clutching vs braking :

A

Clutching transfers torque from an input shaft to an output shaft

Braking stops and holds the load

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5
Q

Three types of misalignment?

A
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6
Q

Can a ridged coupling be used when machines heat up while operating??

A

No they will create misalignment

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7
Q

How does a clamp(muff coupling) transmit force?

A

Keys in the shaft to the coupling

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8
Q

When a clamp (muff) coupling is installed should there be a gap between the half’s?

A

Yes to ensure the coupling is seated all around the shaft.

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9
Q

when torquing a rigid coupling, what sequence do you tighten the bolts?

A

tighten center bolts and work your way to the outside

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10
Q

Rigid couplings are used for low speed or high speed drives?

A

low speed

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11
Q

Three most common categories of flexible couplings?

A

mechanical, elastomeric, universal

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12
Q

What type of coupling is this?

A

Curved tooth gear coupling

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13
Q

although flexible couplings can have slight misalignment why is it advised to get the best alignment as possible?

A

because even with a flexible coupling misalignment will still cause vibration which will transfer to the system causing pre mature bearing failure

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14
Q

jaw a slider couplings are used for low speed and __________ torque situations

A

high

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15
Q

Gear type flexible coupling can accommodate for up to 1 1/2 degrees of angular misalignment and be used for ________ speed applications

A

High

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16
Q

This coupling has higher torque carrying capacity and stiffness than elastomeric coupling?

A

metal grid coupling

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17
Q

this flexible coupling can be used in highspeed applications, is well balanced. this coupling can be used where no backlash is permitted.

A

metallic disc

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18
Q

by increasing or decreasing the number, width, and diameters of the jaws alters the torrsional stiffness torque carrying capacity and overall dimensions.

A

jaw and spider coupling

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19
Q

this coupling shears if forces become to great?

A

unclamped doughnut

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20
Q

Disassembly of this type of coupling can be done without altering or moving hubs ?

A

clamped doughnut couplings

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21
Q
A
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22
Q

Bore of fractured hub shows galling marks

A
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23
Q

Hub keyway is deformed?

A
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24
Q

Internal markings on the bore?

A
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25
Q

Which gear coupling. Can accommodate more misalignment straight tooth or curved tooth

A

Curved tooth

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26
Q

What is a disadvantage of a material flexible coupling?

A

May have a shorter service life then a mechanical flexible coupling

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27
Q

Flexible metal disc couplings are used in either single or double configurations. If a single set of discs is used they tolerate angular misalignment. If the pair is used what can be achieved?

A

Compensate for both angular and offset misalignment.

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28
Q

Flexible metal disc couplings are suitable for unusually high torsional rigidity and is good for _________ compared to many other material flexible couplings.

A

High speeds and high loads

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29
Q

Good coupling for food industry or corrosive environments?

A

Splined rubber coupling

30
Q

What is the correct way to install universal joints, in phase or out of phase? Why?

A

In phase

Prevents excessive vibration.

Prevents speed fluctuations from one joint being magnified by the second joke

31
Q

Universal joint angles must be equal, what joint is meant for unequal joint angles?

A

Constant velocity joint (cv joint)

32
Q

What are the desirable power transmission characteristics with the centrifugal coupling?

A

Soft start - allows drive to approach running speed before applying load

Smooth acceleration - smoothly accelerates with no shock

Overload protection - if overloaded slippage will occur between driver and driven units

Dampening shock - load is achieved because of slight slippage

33
Q

Common couplings for high torque and power applications?

A
  • gear couplings
  • universal joints
  • silent chain couplings
  • flange face couplings
  • flexible metal disc couplings
34
Q

Low horse power couplings?

A

Sleeve
- roller chain
- rubber tire
- steel grid
- jaw and spider
- splined rubber couplings

35
Q

General coupling installation principles?

A
  • rotate equipment by hand first to ensure they rotate freely and smoothly
  • if machines do not rotate freely by hand make sure to correct problem before continuing.
  • inspect shafts for high spots or burs
  • replace shafts with excessive wear or out of roundness
  • measure coupling bore to make sure it matches shaft
  • lubricate shaft
  • read manufactures instructions
  • make sure to leave space between couplings for axial movement
36
Q

Clearance fit couplings are meant for fractional and low horsepower applications. What must be used to keep the couplings in place?

A

Keys and set screws.

Usually 2 set screws, one on the key and the other 90 degrees from it

37
Q

Light press fit couplings require ________ for installation.

A

Hydraulic press or light heating.

38
Q

Installing light press fit tips:

A

Measure shaft using micrometer to ensure coupling is the correct size
- measure coupling using caliper or inside micrometer to ensure correct size
- lubricate shaft and coupling lightly
- carefully press coupling onto shaft watching pressure gauge making sure not to apply to much force and damage parts
- heat may also be used

39
Q

Medium to heavy interference or shrink fit couplings need to be ________ to _______ the bore. What makes the hub grip the shaft?

A

Heated to expand

When the hub cools it shrinks and grips the shaft

40
Q

What are some ways to heat a interference fit coupling?

A

Heating oven
Induction heater
Hot oil bath
Torch

Do not overheat!

41
Q

Installation reminders for interference fit:

A
  • mark final location of hub
  • clean shaft
  • make sure shaft and coupling are correct matches
  • interference fit the bore of the hub should be smaller then shaft
  • instal a stop on the shaft to ensure proper positioning
  • heat coupling overheating can damage coupling
  • slip coupling onto shaft to correct position let cool
  • remove stops and label hub as hot so knowing touches it
42
Q

How much will a steel hub expand for every 180F (83C) above ambient temperature?

A

.001” or .025mm

43
Q

Why don’t you want to drive taper hubs to far up the taper?

A

Over stressed taper bore hubs

44
Q

Oil baths are only capable to of heating up to 300F (150C) for what reason?

A

Risk of fire or explosion

45
Q

Coupling removal guidelines:

A

If coupling worn or damaged inspect to determine cause of wear and correct
- remove locking mechanisms
- use puller holes if provided
- use penetrating oil
- use a soft face or dead blow hammer to no damage hub
- if using a torch to not exceed 600degree F if reusing the shaft

46
Q

Methods of coupling removal?

A

Destructive

Mechanical pullers

Hydraulic injection

47
Q

What is the main difference between clutches and brakes?

A

Clutches are attached to both shafts controlling the transmission from one to another.

Only one half of the brake is attached to to the shaft and the other have is fixed. This allows for holding action of the brake

48
Q

Clutches can either be mechanical or_______?

A

Electromagnetic

49
Q

Three categories of mechanical clutches?

A

Positive contact

Friction

Over-running

50
Q

Positive contact clutches do no have any _______ once engaged. Engagement must happen at very ________speed.

A

Slippage

Low

51
Q

Square jaw positive contact clutches can only be engaged at speeds under 10 rpm. Spiral jaw clutches can be engages at rpm up to _____-?

A

150

52
Q

Multi tooth positive contact clutches can engage smoothly up to ________rpm?

A

300

53
Q

What is the purpose of a torque limiter?

A

Limits torque transmitted to the equipment. An adjustment nut forces a spring washer against a pressure plate which sandwiches the driving element between the friction discs.

54
Q

Different types of over-running clutches?

A

Sprag

Wrap spring

Roller ramp

55
Q

Sprag clutch

A
56
Q

Wrap spring clutches are used in _____\ duty applications?

A

Light

57
Q

This type of over running clutch transmits torque through roller that ride on a ramped or camped surface.

A

Roller ramp clutch

58
Q

What type of clutch is best suited when variable slip is needed?

A

Electromagnetic clutches and brakes

59
Q

Types of electro magnetic clutches?

A

Magnetic particle

Eddy current

Hysteresis

60
Q

What magnetically particle clutch is useful when continuous changes of speed are needed.

A

Magnetic particle

61
Q

Eddy current clutches have an input drum, a stationary field coil and output rotor. They are best suited for variable speed drives but not able to _______ a load.

A

Hold

62
Q

Hysteresis clutches are used in what power applications?

A

Fractional horse power

Wear well and have long service life

63
Q

Clutch and brake actuation methods?

A

Mechanical

Electrical

Pneumatic

Hydraulic

Self activating

64
Q

Simplest and cheapest way to engage clutches and brakes?

A

Mechanical

Uses a series of rods, cables, levers, or cams

65
Q

_______ actuated clutches have limited torque range, but allow very cycling rates.

A

Electrically activated

Expensive but convenient

66
Q

Two basic parts of electromagnetic clutch or brake?

A

Annular electromagnet (coil) and an armature

67
Q

Most popular actuation method in industrial equipment?

A

Pneumatic

68
Q

Main advantage of pneumatic actuation?

A

Low heat generation, low power requirements, simple to maintain.

69
Q

To operate effectively pneumatic operated clutches and brakes they need the the following components:

A

Filter
Lubricator
Control valve
Pressure regulator
Quick exhaust
Exhaust muffler

70
Q

Hydraulic actuated clutches offer smooth engagement and fast response. What is the main disadvantage?

A

Cost of supporting equipment

71
Q

Self activating clutches use centrifugal force to create wedging or wrapping action. These clutches provide _________ with slip and use little energy.

A

Gentle starts

Red Seal Study Prep (5 decks)

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