6.9 Transmission Flashcards
Where are external spur gears used?
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
Where are internal spur gears used?
An internal gear would be used where a change in speed is required without changing the axis of drive.
What is backlash and what is it used for?
Backlash is the lost motion between the gear teeth.
Used for thermal expansion and
Lubrication
What type of gear is made with a “spider” and “sun” section?
Planetary Gear System
Two gear drive shafts transmitted at an angle to each other would be what type of gear?
Bevel Gear
What kind of gears would be used if the loads to be transmitted are light and quietness is required?
Helical Gear
What are the advantages of using a helical gear over a spur gear?
A helical gear is smoother and is a less noisy running gear than the spur gear.
If a drive were to be transmitted through an angle of 90 degrees, what type of gear would be used?
Bevel Gear
What is the purpose of an idler gear?
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
What are planetary gears used for?
Planetary gear systems are typically used to reduce the propeller shaft speed on more powerful aircraft engines
How would you gain mechanical advantage using gears?
The number on either the drive or driven gear is varied.
Mechanical Advantage = Driven Gear teeth / Drive Gear teeth
If you needed an output gear to turn in the same direction as the input gear what would you use?
Idler Gear
If in a gear train, the drive gear has 50 teeth and the driven gear has 100 teeth, what is the mechanical advantage gained?
2
Mechanical advantage = Driven Gear Teeth / Drive Gear teeth
What type of gear system is used when an extreme amount of mechanical advantage is needed?
Worm Gear
What class of lever is a single pulley, which is not fixed?
First class lever
What is a common method of determining the mechanical advantage of a pulley system?
Mechanical advantage is the same as number of wheels/pulleys
or Count number of movable ropes
Name the common types of belt assemblies that you have studied?
‘V’ belt drive and Pulleys
What type of belt assembly used friction as the turning force?
‘V’ Belt drive
Describe a hollow saddle key?
‘Hollow section in pulley’
One face hollowed to suit the surface of the shaft, the pulley has the key
Pulleys are normally attached to a rotating shaft by the use of keys - explain?
A key is a method of attaching the pulley to the shaft/
- Hollow saddle (Pulley) Key
- Flat Saddle Key
- Woodruff Key
What is a chain used on a control run for some flight controls (2 reasons)?
Chains
Transfer motion from one point to another
Used where considerable force is required such as on an aileron and elevator
What advantage do detachable chains have over other types of chains?
The main advantage of a detachable chain is the ease at which any link can be removed.
What are the three principal dimensions on a standard roller chain?
1 Pitch
- Width between inner plates
- Roller Diameter
What part of a chain assembly is used when the chain has to change direction?
Bi-Planar Block
List four types of sprockets used with roller chains?
Heat treated to get teeth harder for increased wear resistance
What type of treatment process would be carried out on the teeth of a steel sprocket?
Heat treatment to get teeth of gear hard to resist wear
How is the Backlash of a gear mesh measured?
DTI
Dial Test Indicator
What is the gear ratio of two meshed gears?
Gear Ratio = Number of teeth on large gear / Number of teeth on small gear
