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Enriched Science > Mechanical Engineering > Flashcards

Mechanical Engineering Flashcards

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1
Q

Define Mechanical Engineering:

A

focuses on the design, production, analysis, working and improvement of a technical object with moving parts

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2
Q

What is the function of guidance?

A

Guidance is the function of a part that directs another part along a specific path. The mechanical function performed by any component that controls the motion of one or more moving parts. A guiding component or control is a component whose mechanical function is to guide the motion of moving parts.

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3
Q

Guidance dictates whether the motions is….

A

Guidance dictates whether the motion is either rotational (wheel and axle), translational (sliding drawer) or helical (C clamp)

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4
Q

What to guidance and links between parts allow for?

A

Guidance and Links between parts allow for the restriction of motion that would otherwise impede the proper function of the mechanism.

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5
Q

What does Translational guidance ensure?

A

Ensures the straight translational motion of a moving part . ( A track at the bottom and top of a window is an example of this)

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6
Q

What does rotational guidance ensure?

A

Ensures the rotational motion of a moving part. ( An example is the axle attached tot he bicycle frame guides the wheel in a rotational motion).

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7
Q

What does helical guidance ensure?

A

Ensures the translational motion of a moving part while it rotates around the same axis. ( An example is the threads inside a C clamp controls the helical guiding of the threaded shank).

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8
Q

Describe motion:

A

If an object could exist totally independent from any other object it would have 6 degrees of motion freedom, - translation along 3 axis, and rotation around the same three axis.

2 translations and 2 rotations around 3 different axis result in 12 different potential motions.

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9
Q

Define linking:

A

As soon as a technical object contains two or more parts, an engineer must find a way to hold them together.

Linking is the mechanical function performed by any component that connects different parts of technical objects.

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10
Q

List the Characteristics of links and define each as you go:

A 
1.Direct - held without a link
Indirect - held with a link
2. Rigid or Flexible?
	- can it be deformed like a spring
3. Removable or Non-Removable?
	- separated without damage or not
4. Complete - prevented from moving independently 
Partial - move independently
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11
Q

Describe Motion Transmission:

A

Relaying a motion from one part to another without altering the nature of the motion.

A motion transmission system is a set of components that perform the function of transmitting motion.

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12
Q

What does the driver component do?

A

Receives the force

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13
Q

What does the driven component do?

A

Receives the motion and transfers it to another part.

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14
Q

What does the intermediate component do?

A

located between the driver and driven component.

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15
Q

Characteristics of motion in mechanical engineering systems are often applied to technical objects….

A

All transmit rotational motion

  • The direction of the rotation of the components may be identical throughout or different.
  • Clockwise or counter clockwise
  • The system may or may not be reversible.
  • If it is reversible then the driven component can become a driver and vice versa.
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16
Q

Gears are often used for one of the following reasons…

A

To reverse the direction of rotation

To increase or decrease the speed of rotation

To move rotational motion to a different axis

To keep the rotation of two axis synchronized

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17
Q

What is the gear ratio?

A

teeth on follower divided by # teeth on driver

teeth on follower/ # teeth on driver

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18
Q

1) Low gear ratio =…..

2) High gear ration=

A

1) Low gear ratio=more speed = less force

2) High gear ratio= less speed = more force

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19
Q

What does the speed change in motion transmission depend on?

A

Depends on the relative diameters of the driver and driven components.

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20
Q

What does it mean when the speed increases?

A

Diameter of Driver > diameter of driven
* When the diameter of the driver component is greater than the diameter of the driven component, there is a speed increase in the system.

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21
Q

What does it mean when there is a speed decrease?

A

Diameter of driver < diameter of driven

  • When the diameter of the driver component is less than the diameter of the driven component, there is a speed decrease in the system.
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22
Q

What does it mean when there is no speed change?

A

Diameter of driver = diameter of driven
* When the diameter of the driver component is equal tot he diameter of the driven component, there is no speed change in the system.

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23
Q

Speed ratio:

A

The speed ratio can be used to describe the speed change for a system.

Speed ratio= diameter or number of teeth of driver component/ diameter or number of teeth of driven component.

  • If speed ration= 1, then there is no change in speed
  • If the speed ration is >1, then there is an increase in speed
  • If the speed ration is <1, then there is a decrease in speed.
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24
Q

Describe “ Gear Assembly”:

A
  • Rotational is transmitted from one gear to another
  • Rotation direction is opposite in each connecting gear
  • System can have more than two gear wheels
  • Used in machinery where mechanical advantage is needed
  • The torque ( force) of a small motor can be increased considerably through a gear train
  • Requires fine machining of parts so that the teeth fit together precisely
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25
Q

Are gear trains reversible?

A

Yes

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26
Q

What are the advantages to gear trains?

A
  • Will not allow slippage
  • Can be connected at various angles
  • Allows for large forces to transmitted
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27
Q

What are the disadvantages to gear trains?

A
  • Needs lubrication
  • Subject to severe damage if there is a failure in any one part of the system
  • Requires elaborate machining
28
Q

If the gears are no longer touching they are called…

A

Sprockets

29
Q

Describe Sprocket and wheels chain:

A
  • Rotational motion is transmitted from one sprocket to the other by a chain
  • Rotation direction is opposite in each connecting sprocket
  • System can have more than two sprockets
  • Used in machinery where mechanical advantage is needed
  • The teeth of sprockets must be identical so that one chain securely fits all the sprockets
  • In a given system, the smaller the sprocket the faster it will rotate
30
Q

Is a sprocket wheels and chain reversible?

A

Yes

31
Q

What are the advantages of sprocket wheels and chain?

A
  • Will not allow slippage

* Allows for large forces to be transmitted

32
Q

What are the disadvantages of the sprocket wheels and chain?

A
  • Needs lubrication
33
Q

Give a brief explanation of the wheel and worm gear:

A

Worm gears are used when large gear reductions are needed. It is common for worm gears to have reductions of 20:1, and even up to 300:1 or greater.

For each 360° turn of the worm, the worm-gear advances only one tooth of the gear.

The worm is the driver. The opposite will not work.

34
Q

Describe the wheel and worm gear:

A
  • Rotational motion is transmitted from the worm gear to one or more wheel gears (sprocket)
  • Used in machinery where fine adjustment is needed
  • One turn of the worm gear advances the wheel by one tooth.
  • Requires fine machining of parts so that the wheel gear teeth fit precisely in the worm gear.
35
Q

Is the wheel and worm gear reversible?

A

No. If a force is applied to the wheel gear ( sprocket) the worm gear will not turn.

36
Q

What are the advantages to the wheel and worm gear?

A
  • Will not allow slippage

* Allows for fine adjustment (eg turning pegs on a guitar)

37
Q

What are the disadvantages to the wheel and worm gear?

A
  • Needs lubrication
38
Q

Give a brief explanation of friction gear systems:

A
  • Similar to a gear train, however the friction gears do not have teeth
  • Less efficient than gear trains because the gears can slip.
39
Q

Describe friction gears:

A
  • Rotational motion is transmitted from one wheel to the other
  • Transmission is done by friction between wheels
  • Rotation direction is opposite in each connecting wheel
40
Q

Are friction gears reversible?

A

Yes

41
Q

What are the advantages to friction gears?

A
  • easy to assemble
  • inexpensive to make
  • will allow slippage, protecting it from damage
  • Gears can be placed perpendicular or at any angle to eachother
42
Q

What are the disadvantages to friction gears?

A
  • Wheels must always be together even as they wear away

* Wheels can slip, causing interruption in transmission of motion

43
Q

What are the disadvantages to friction gears?

A
  • Wheels must always be together even as they were away
  • Wheels can slip, causing interruption in transmission of motion
  • Must be kept clean (free of lubricants)
44
Q

Give a brief description of the belt and pulley system:

A
  • Similar to a chain and sprocket however, there are no teeth.
  • The gear without teeth is called the pulley.
  • The chain is called the belt.
45
Q

Describe the belt and pulley system:

A
  • Rotational motion is transmitted from one pulley to the other by a belt
  • Rotation direction is opposite in each wheel
  • System can have more than two wheels
46
Q

Is the pulley and belt reversible?

A

Yes

47
Q

What are the advantages to pulley and belt?

A
  • easy to assemble
  • will allow slippage, protecting it from damage
  • allow for transmission of motion over long distance e.g ski lift
48
Q

What are the disadvantages to pulley and belt?

A
  • Slippage will occur with wear and improper tension on the belt
  • Belt and Pulleys must be kept clean ( free of lubricants)
  • Belt can be subject to premature wear
49
Q

What are the characterisitcs of motion in transformation systems?

A

*Mechanical action that changes the nature of motion (rotation to translation, translation to rotation)

50
Q

Describe the rack and pinion:

A
  • Rotational motion of pinion is transformed into translational motion of rack.
  • Translational motion can be applied to rack produce rotational motion in the pinion.
  • The rack is really a toothed gear wheel that has been straightened.
51
Q

Is the rack and pinion reversible?

A

Yes because rotational motion can be applied tot he pinion to produce translational motion in the rack and vice versa.

52
Q

What are the advantages to the rack and pinion?

A
  • Allows force to be applied without slippage
53
Q

What are the disadvantages to the rack and pinion?

A
  • Parts need to be lubricated

* Very precise fit needed between teeth of rack and pinion

54
Q

What are the two types to the screw gear system?

A

Type 1) Nut is free component. Screw is fixed component.

Type 2) Screw is free component. Nut is fixed component

55
Q

Is the Screw Gear system reversible?

A

No, because you cannot transform translational to rotational motion in this system.

56
Q

What are the advantages to the screw gear system?

A
  • Allows for precise adjustment in it’s use. Used in many types of tools and machinery.
57
Q

What are the disadvantages to the screw gear system?

A
  • Parts need to be lubricated
58
Q

Give a brief description of the cam and follower systems?

A

Rotational motion of the cam is transformed into translational motion of the slider.

59
Q

Describe the cam and follower:

A
  • Rotational motion can be applied to cam to create translational motion on the follower. The follower must have guidance of some sort to operate properly.
  • Size and shape of cam and placement of axle will determine the length and action of the stroke.
60
Q

Is the cam and follower reversible?

A

No, because applying a force to the follower ( moving it up and down) will not cause the cam to rotate.

61
Q

What are the advantages to the cam and follower?

A
  • Allows for very precise and custom translational motion. Timing and distance of the follower can be determined by shape, size of cam and placement of axle on cam.
62
Q

What are the disadvantages of the cam and follower?

A
  • Parts need to be lubricated

* A return mechanism (e.g spring, gravity has to be built into design).

63
Q

Give a brief description of the slider-crank mechanism:

A
  • Translational motion of the piston is transformed into rotational motion of the crank. Reversible!
64
Q

Define the (rotating)slider crank mechanism:

A
  • Rotational motion is transformed to translational motion in the slide
  • Translational motion of the slide is transformed into partial rotational motion in the crank.
  • Provides a mechanical advantage which is determined by the size of the wheel
  • Produces oscillating motion.
65
Q

Is the slider crank mechanism reversible?

A

Yes, because rotational motion of the crank produces translational motion in the slide and translational motion of the slide produces partial rotational motion in the crank.

66
Q

What are the advantages to the slider crank mechanism?

A
  • Changes motion from translational to rotational or vice versa
67
Q

What are the disadvantage s of the slider crank mechanism?

A
  • Parts need to be lubricated

* Reversibility is only partial

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