6.9

Question 1

Why are spur gears used ?

Answer 1

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 )

Question 2

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

Answer 2

True

Question 3

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

Answer 3

Larger gear - wheel ( spur )
Smaller gear - pinion

Question 4

Whats the two spur gears ?

Answer 4

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

Question 5

What gear is a modification of a spur gear ?

Answer 5

Helical gears - carry heavier loads, quiet

Question 6

Whats the Two types of helical gears ?

Answer 6

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

Question 7

Where are bevel gears used ?

Answer 7

between intersecting shafts

Question 8

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

Answer 8

Run quieter
Carry greater loads

Question 9

What does hypoid gears require for them to not slide ?

Answer 9

Extreme pressure lubricant
( quieter and smoother than bevel gears )

Question 10

What does worm gears connect ?

Answer 10

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

Question 11

What makes worm gear highly inefficient to other gears ?

Answer 11

Large sliding movement in teeth

Question 12

Where is worm gear used ?

Answer 12

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

Question 13

Why is a rack and pinion gear system used ?

Answer 13

To transmit motion between rotating spur gears and toothed rack.

Question 14

What motions does a rack and pinion gear convert ?

Answer 14

Rotational to linear

Question 15

Where is rack and pinion gears used ?

Answer 15

Leading edge flaps

Question 16

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

Answer 16

Number of teeth must be different.

Question 17

Whats the calculation to find gear ratio

Answer 17

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

Question 18

Note : drive gear rpm is 2x driven gear rpm

Question 19

Where are idler gears used and why ?

Answer 19

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 )

Question 20

Whats the purpose of a reduction gear ?

Answer 20

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

Question 21

What gear is used as a reduction gear ?

Answer 21

Epicyclic ( planet ) gear

Question 22

What gears is a planet gear made from ?

Answer 22

1. Sun gear
2. Planet gear
3. Ring gear ( fixed )

Question 23

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

Answer 23

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

Question 24

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

Answer 24

Meshing and patterns.

Question 25

What does gear backlash ?

Answer 25

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

Question 26

What is a belt ?

Answer 26

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

Question 27

How can a belt drive change the speed of rotation ?

Answer 27

Using different sized pulleys

Question 28

Whats the two belt types ?

Answer 28

1. Friction drive belts 2. Positive drive belts

Question 29

Whats 1 advantages of using flat belts ?

Answer 29

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.

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

When would you use a timing belt ?

Answer 32

Where exact synchronisation between driver and driven shaft is required.

Question 33

What can cause a drive to be noisy ?

Answer 33

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

Question 34

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

Answer 34

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

Question 35

What advantages does a synchronous pulley have ?

Answer 35

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

Question 36

Why would you use a stepped or cone pulley drive ?

Answer 36

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

Question 37

What does a chain engage with to transmit power ?

Answer 37

Sprocket

Question 38

What’s the use of a chain ?

Answer 38

To transmit motion between two sprockets

Question 39

What is the sprocket called on the driven shaft ?

Answer 39

Driver sprocket.

Question 40

Whats the two types of chains ?

Answer 40

1. Leaf chain 2. Roller chain

Question 41

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

Answer 41

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

Question 42

What does leaf chains run over rather than sprockets ?

Answer 42

Sheaves

Question 43

Whats an advantage for chain drives ?

Answer 43

Don’t slip because of teeth.

Question 44

Whats a disadvantage for chain drives ?

Answer 44

There heavy and noisy and expensive