6.9 Transmission

Question 1

Where are external spur gears used?

Answer 1

External spur gears are used where a change in speed is required but the shafts lie parallel to each other.

They rotate in opposite directions

Question 2

Where are internal spur gears used?

Answer 2

An internal gear would be used where a change in speed is required without changing the axis of drive.

Question 3

What is backlash and what is it used for?

Answer 3

Backlash is the lost motion between the gear teeth.

Used for thermal expansion and

Lubrication

Question 4

What type of gear is made with a “spider” and “sun” section?

Answer 4

Planetary Gear System

Question 5

Two gear drive shafts transmitted at an angle to each other would be what type of gear?

Answer 5

Bevel Gear

Question 6

What kind of gears would be used if the loads to be transmitted are light and quietness is required?

Answer 6

Helical Gear

Question 7

What are the advantages of using a helical gear over a spur gear?

Answer 7

A helical gear is smoother and is a less noisy running gear than the spur gear.

Question 8

If a drive were to be transmitted through an angle of 90 degrees, what type of gear would be used?

Answer 8

Bevel Gear

Question 9

What is the purpose of an idler gear?

Answer 9

To make output gear rotate in the same direction of input gaer or

To link the gears when there is a gap between the drive and driven gears

Question 10

What are planetary gears used for?

Answer 10

Planetary gear systems are typically used to reduce the propeller shaft speed on more powerful aircraft engines

Question 11

How would you gain mechanical advantage using gears?

Answer 11

The number on either the drive or driven gear is varied.

Mechanical Advantage = Driven Gear teeth / Drive Gear teeth

Question 12

If you needed an output gear to turn in the same direction as the input gear what would you use?

Answer 12

Idler Gear

Question 13

If in a gear train, the drive gear has 50 teeth and the driven gear has 100 teeth, what is the mechanical advantage gained?

Answer 13

2

Mechanical advantage = Driven Gear Teeth / Drive Gear teeth

Question 14

What type of gear system is used when an extreme amount of mechanical advantage is needed?

Answer 14

Worm Gear

Question 15

What class of lever is a single pulley, which is not fixed?

Answer 15

First class lever

Question 16

What is a common method of determining the mechanical advantage of a pulley system?

Answer 16

Mechanical advantage is the same as number of wheels/pulleys

or Count number of movable ropes

Question 17

Name the common types of belt assemblies that you have studied?

Answer 17

‘V’ belt drive and Pulleys

Question 18

What type of belt assembly used friction as the turning force?

Answer 18

‘V’ Belt drive

Question 19

Describe a hollow saddle key?

Answer 19

‘Hollow section in pulley’

One face hollowed to suit the surface of the shaft, the pulley has the key

Question 20

Pulleys are normally attached to a rotating shaft by the use of keys - explain?

Answer 20

A key is a method of attaching the pulley to the shaft/

1. Hollow saddle (Pulley) Key
2. Flat Saddle Key
3. Woodruff Key

Question 21

What is a chain used on a control run for some flight controls (2 reasons)?

Answer 21

Chains

Transfer motion from one point to another

Used where considerable force is required such as on an aileron and elevator

Question 22

What advantage do detachable chains have over other types of chains?

Answer 22

The main advantage of a detachable chain is the ease at which any link can be removed.

Question 23

What are the three principal dimensions on a standard roller chain?

Answer 23

1 Pitch

2. Width between inner plates
3. Roller Diameter

Question 24

What part of a chain assembly is used when the chain has to change direction?

Answer 24

Bi-Planar Block

Question 25

List four types of sprockets used with roller chains?

Answer 25

Heat treated to get teeth harder for increased wear resistance

Question 26

What type of treatment process would be carried out on the teeth of a steel sprocket?

Answer 26

Heat treatment to get teeth of gear hard to resist wear

Question 27

How is the Backlash of a gear mesh measured?

Answer 27

DTI

Dial Test Indicator

Question 28

What is the gear ratio of two meshed gears?

Answer 28

Gear Ratio = Number of teeth on large gear / Number of teeth on small gear

Question 29

Answer 29