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Mechanical Devices Flashcards

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1
Q

What do mechanical devices do?

A

Mechanical devices change an input force and movement into a desired output force and movement.

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2
Q

What can mechanisms change?

A

Mechanisms can change the magnitude and direction of force.

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3
Q

What is input in a mechanism?

A

Force and movement are input into a mechanism.

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4
Q

What does a mechanism do?

A

The mechanism converts or transmits the input force and movement into an output force and movement.

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5
Q

What is output in a mechanism?

A

Force and movement are output to satisfy a need.

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6
Q

What can mechanisms be used for?

A

Mechanisms can be used to make a force bigger or smaller.

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7
Q

What types of movement can mechanical devices produce?

A

Mechanical devices can produce linear, reciprocating, rotary, and oscillating movement.

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8
Q

What is a gear train?

A

Gear trains consist of gears that transmit torque (the turning force).

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9
Q

What is the role of the input gear in a gear train?

A

The input gear drives the system.

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10
Q

What is the role of the output gear in a gear train?

A

The output gear receives the motion from the input gear.

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11
Q

What is linear movement?

A

Movement in a straight line in one direction.

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12
Q

What is inclined plane movement?

A

Movement in a straight line in two directions.

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13
Q

What is screw movement?

A

Rotational movement on or around an axis.

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14
Q

What is oscillating movement?

A

Movement back and forth along a curved path.

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15
Q

What is mechanical advantage (MA)?

A

Mechanical advantage (MA) is a measure of the force amplification achieved by using a mechanism.

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16
Q

How is mechanical advantage calculated?

A

MA = Load / Effort.

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17
Q

What are gears?

A

Gears are toothed wheels attached to shafts used to transmit power and rotational motion around mechanical systems.

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18
Q

What is a gear train?

A

Gear trains consist of two or more interlocking gears that transmit torque and rotary motion.

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19
Q

What is the driver gear?

A

The input gear is the driver gear.

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20
Q

What is the driven gear?

A

The output gear is the driven gear.

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21
Q

What happens when the driver gear rotates clockwise?

A

If the driver gear rotates clockwise, the driven gear rotates anticlockwise and vice versa.

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22
Q

How can the direction of rotation of the driven gear be changed?

A

The direction can be changed by adding an idler gear.

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23
Q

What is the role of the idler gear?

A

The idler gear changes the direction of rotation so that both the driver gear and driven gear move in the same direction.

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24
Q

Does the size of the idler gear matter?

A

The size of the idler gear does not matter; it transfers the movement without altering the speed of the gears.

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25
How can you create a faster output speed?
To make the output speed faster, the input gear must be larger than the output gear.
26
How can you create a slower output speed?
To make the output speed slower, the input gear must be smaller than the output gear.
27
How do you calculate gear ratios?
The larger gear always equals 1. The smaller gear is calculated by dividing the number of teeth on the larger gear by the number of teeth on the smaller gear.
28
What is the gear ratio for a driver gear with 40 teeth and a driven gear with 20 teeth?
Driver = 1, Gear Ratio = 1:2 ## Footnote 1 turn of the driver gear = 2 turns of the driven gear.
29
What is the gear ratio for a driver gear with 10 teeth and a driven gear with 30 teeth?
Driver = 3, Gear Ratio = 3:1 ## Footnote 3 turns of the driver gear = 1 turn of the driven gear.
30
What are cam mechanisms used for?
Cam mechanisms are used to convert rotary motion into reciprocal motion.
31
What are the main components of a cam mechanism?
A cam mechanism consists of a cam and a follower.
32
What is a cam?
A cam is a specially shaped piece of material attached to a rotating shaft.
33
What does the follower do in a cam mechanism?
A follower rests on the cam and rises and falls as the cam rotates, creating a reciprocating motion.
34
What actions can the follower perform depending on the cam shape?
The follower can rise, fall, or dwell (remain stationary).
35
What additional components might a cam mechanism include?
A cam mechanism may include a slide, a crank, and a wheel follower.
36
What is the purpose of a slide in a cam mechanism?
A slide prevents the follower from slipping.
37
What is the purpose of a crank in a cam mechanism?
A crank is used to manually rotate the camshaft.
38
What is the function of a wheel follower?
A wheel follower reduces friction between the cam and follower.
39
What are some common types of cams?
Common types of cams include Eccentric (Circular), Pear-Shaped, Heart-Shaped (Constant Velocity), and Snail.
40
Describe the Eccentric (Circular) cam.
The pivot is positioned off-centre, causing the follower to steadily rise and fall.
41
Describe the Pear-Shaped cam.
The follower dwells for half a turn, rises for a quarter turn, and falls for the last quarter rotation.
42
Describe the Heart-Shaped cam.
The follower gradually rises and then suddenly drops, rotating in only one direction.
43
Describe the Snail cam.
The follower rises and falls with no dwell period, exhibiting constant velocity.
44
What is a simple fixed pulley mechanism?
A simple fixed pulley mechanism is made up of a rimmed wheel and cable, which sits inside the rimmed wheel. It provides no mechanical advantage but can make items easier to lift by changing the direction of force.
45
How can using multiple pulleys reduce the force required to lift a load?
Using two or more pulleys together in a block and tackle system can reduce the magnitude of force required to lift a load. The example shown will halve the required input force to lift the load.
46
What is the purpose of a belt in a belt and pulley system?
In a belt and pulley system, a belt connects two or more pulleys to transfer rotary motion and force from the driver pulley to the driven pulley.
47
Why are belts often made of rubber in pulley systems?
Belts need to remain taut, so they are often made of rubber to reduce slippage.
48
How can belts be arranged to change output movement?
Belts can be crossed to change the direction of the output movement.
49
What happens when the driver pulley is larger than the driven pulley?
When the driver pulley is larger than the driven pulley, the driven pulley will rotate faster, but the torque will be less.
50
What happens when the driver pulley is smaller than the driven pulley?
When the driver pulley is smaller than the driven pulley, the driven pulley will rotate slower, but the torque will be greater.
51
How is the velocity ratio calculated in a pulley system?
The velocity ratio can be calculated using the formula: Velocity ratio = Diameter of driven pulley / Diameter of driver pulley.
52
What does a velocity ratio of 3:1 indicate?
A velocity ratio of 3:1 indicates that the driver pulley will rotate three times slower than the driven pulley, but the torque of the driven pulley will be greater.
53
What is a lever?
A lever is a mechanical device used to transmit and transform the effects of forces.
54
What are the three parts of a lever?
Load, Effort, Fulcrum/Pivot.
55
What is the input force in a lever?
The input force (effort) is transmitted through the lever to move the load.
56
What characterizes a first order lever?
In a first order lever, the fulcrum is positioned between the load and the effort.
57
How can the input effort be reduced in a first order lever?
The input effort required to lift the load can be reduced by moving the fulcrum closer to the load.
58
Give examples of first order levers.
Scissors, Seesaw, Crowbar.
59
What characterizes a second order lever?
In a second order lever, the load is positioned between the fulcrum and the effort.
60
How can the input effort be reduced in a second order lever?
The input effort required to lift the load can be reduced by moving the load closer to the fulcrum.
61
Give examples of second order levers.
Bottle opener, Wheelbarrow, Nutcracker.
62
What is a third order lever?
In a third order lever, the effort is applied between the fulcrum and the load.
63
How does the mechanical advantage of third order levers compare to first and second order levers?
Third order levers do not have the mechanical advantage of first order and second order levers.
64
Where is the effort located in a third order lever?
The effort is closer to the fulcrum than the load.
65
What is the relationship between input effort and output force in third order levers?
The input effort is greater than the output force.
66
What are some examples of third order levers?
Fishing rod, Tweezers, The human arm.
67
What are linkages in the context of levers?
Linkages are levers joined together to change an input motion + force into an output motion + force.
68
What is the function of linkages?
They often transmit force and motion at a distance from the initial input.
69
What is a push/pull linkage?
A push/pull or parallel motion linkage creates an identical parallel motion at the output.
70
What does a bell crank linkage do?
A bell crank linkage changes the direction of motion through 90 degrees.
71
How can the output force be made greater than the input force in a linkage?
Move the fixed point closer to the output.
72
What is the significance of the fixed point in a linkage?
The fixed point (pivot) is an equal distance from the input and output levers.

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