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M6 > 6.9 > Flashcards

6.9 Flashcards

1
Q

Why are spur gears used ?

A
  1. Increase or decrease speed of a device
  2. Multiply torque by transmitting power and motion from one shaft to another.
    ( spur gears are noisy )
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2
Q

Spur gears connect parallel shafts only.. true or false ?

A

True

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3
Q

When two spur gears of different sizes mesh together, what’s the larger and smaller gear called ?

A

Larger gear - wheel ( spur )
Smaller gear - pinion

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4
Q

Whats the two spur gears ?

A

External spur gears - used when shafts are parallel to each other
Internal spur gears - Maintains diameter

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5
Q

What gear is a modification of a spur gear ?

A

Helical gears - carry heavier loads, quiet

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6
Q

Whats the Two types of helical gears ?

A

Single helical - transmit more power than straight cut gears
Double helical - transmit more force

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7
Q

Where are bevel gears used ?

A

between intersecting shafts

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8
Q

What does curved teeth on bevel gear allow it to do ?

A

Run quieter
Carry greater loads

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9
Q

What does hypoid gears require for them to not slide ?

A

Extreme pressure lubricant
( quieter and smoother than bevel gears )

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10
Q

What does worm gears connect ?

A

Non-intersecting shafts
( worm gears offers high reductions in single steps )

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11
Q

What makes worm gear highly inefficient to other gears ?

A

Large sliding movement in teeth

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12
Q

Where is worm gear used ?

A

Flap control systems.
( places which have to be driven in both directions ( up and down )

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13
Q

Why is a rack and pinion gear system used ?

A

To transmit motion between rotating spur gears and toothed rack.

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14
Q

What motions does a rack and pinion gear convert ?

A

Rotational to linear

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15
Q

Where is rack and pinion gears used ?

A

Leading edge flaps

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16
Q

What must be different on either driven gear or drive gear to gain a mechanical advantage ?

A

Number of teeth must be different.

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17
Q

Whats the calculation to find gear ratio

A

Number of teeth on driven gear divided by number of teeth on drive gear

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18
Q

Note : drive gear rpm is 2x driven gear rpm

A
19
Q

Where are idler gears used and why ?

A

Between two other gears to :
1. To link two distant gears
2. To make output gear rotate same direction as input gear
( presence of idler gear makes no difference to ration speed )

20
Q

Whats the purpose of a reduction gear ?

A

To allow both engine and prop to operate within their most efficient speed.

21
Q

What gear is used as a reduction gear ?

A

Epicyclic ( planet ) gear

22
Q

What gears is a planet gear made from ?

A
  1. Sun gear
  2. Planet gear
  3. Ring gear ( fixed )
23
Q

What happens if the gears teeth are meshed to highly and to low ?

A

High - load is transmitted to small portion of teeth causing them to brake.
Low - teeth cannot be lubricated.

24
Q

Whats the two most important factors when it comes to mating two gears ?

A

Meshing and patterns.

25
Q

What does gear backlash ?

A

Clearance between teeth and meshing point.
( prevents over heating and allows for lubrication )

26
Q

What is a belt ?

A

Flexible material used to link or drive two or more rotating shafts
( assembled parallel )

27
Q

How can a belt drive change the speed of rotation ?

A

Using different sized pulleys

28
Q

Whats the two belt types ?

A
  1. Friction drive belts
  2. Positive drive belts
29
Q

Whats 1 advantages of using flat belts ?

A
  1. Due to being driven off friction it eliminates the need for high tension, reducing shaft and bearing loads.

( flat belts are not advisable for high outputs at high speeds as the belt could slip.

30
Q

Whats the V-shape on a V-belt allow ?

A

Allows fast moving belts to stay in grooves better than it is to keep a flat belt on a pulley

31
Q

What good features does a V- ribbed belt and V- belt have ?

A

V-ribbed belt - ribs ensure belt tracks properly
V-belt - runs efficiently and can be ran at high speeds

32
Q

When would you use a timing belt ?

A

Where exact synchronisation between driver and driven shaft is required.

33
Q

What can cause a drive to be noisy ?

A
  1. If belt teeth don’t match with pulley grooves.
  2. If belt wears from ratcheting.
34
Q

What differs a V-belt pulley to other types of pulleys ?

A

V-belt pulleys have deep grooves which guide and gain traction

35
Q

What advantages does a synchronous pulley have ?

A
  1. Non-lubricated
  2. Non-slip
  3. Long lives
  4. Quiet
36
Q

Why would you use a stepped or cone pulley drive ?

A

Where different operational speeds can be produced by changing belt to a different pulley size.

37
Q

What does a chain engage with to transmit power ?

A

Sprocket

38
Q

What’s the use of a chain ?

A

To transmit motion between two sprockets

39
Q

What is the sprocket called on the driven shaft ?

A

Driver sprocket.

40
Q

Whats the two types of chains ?

A
  1. Leaf chain
  2. Roller chain
41
Q

Why are leaf chains not used as much as roller chains ?

A

As leaf chains need frequent lubrication and can only be used for low speed applications.

42
Q

What does leaf chains run over rather than sprockets ?

A

Sheaves

43
Q

Whats an advantage for chain drives ?

A

Don’t slip because of teeth.

44
Q

Whats a disadvantage for chain drives ?

A

There heavy and noisy and expensive

M6 (6 decks)

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