6.9 Flashcards
What is used to change direction of control runs?
Chains
What is meant by pitch in relation to chains?
The distant between the centre of chain links
What is a bi-planer block?
A mechanical link that turns a chain 90°
Why must a chain wheel have more than 12 teeth?
The wear will be too high otherwise
What is the minimum amount of teeth on a gear chain?
17
Why are chain retainers used?
To prevent the chain jumping from the sprocket
Why are couplings used?
To connect two shafts together?
What are the different types of couplings?
- solid coupling
- safety coupling
- movable and disconnectable couplings
What are the two types of solid couplings?
Disk and sleeve couplings
Where are disk couplings used on voyager?
Slat drive shafts
When are movable couplings used?
When shafts are not aligned or if position changes during operation
When are extension couplings used?
When small longitudinal movement is needed (such heating during operation)
What is a drive gear?
A gear that is giving an input/ driving into something
What is a driven gear?
When a gear is being driven by something
If a drive gear is turning clockwise, what direction is the driven gear turning?
Anti-clockwise
How do you gain mechanical advantage when using gears?
By having gears with different amount of teeth
How do you reduce the noise of toothed-wheel gears?
Ground tooth flanks and operate in oil
When are external spur gears used?
When a change of speed is required and shafts lie parallel to each other
When are internal spur gears used?
When a change of speed is required whilst maintains an overall minimum diameter
What is the smallest of the pair of spur gears referred as?
The pinion
What is the largest of the pair of spur gears referred as?
The spur
What is special about the internal spur gear?
Both gears turn the same direction
Why do helical gears transmit more power that straight gears?
More teeth in mesh for larger contact area
Why is a rack and pinion used?
When you want to transform rotational motion into linear motion
How does a worm gear work?
A gear will rotate and turn a spiral shaft to make it spin
When are beverages gears used?
When transmitting the drive between shafts which have intersecting axes (two shafts at 90°)
What angle should the teeth on a herringbone gear not exceed?
20°
When are herringbone gears used?
When transmitting large forces
What is meant by gear ratio?
The ration of the rotational speeds of multiple gears
What happens if the drive gear is bigger than the driven gear?
The smaller driven gear will rotate quicker
What is the formula for gear ratios?
T2/T1
teeth on gear 2/ teeth on gear 1
What is meant by backlash?
The clearance between gear teeth at the point of mesh
Why must you have some backlash in gears?
To allow for lubrication and expansion
What would happen if the backlash was too high?
The gears would start to wear
What is meant by meshing?
The point at which the teeth are engaged with each other and ready to transmit power
If you have a larger mesh angle what does this mean to the gear teeth?
They are also larger
Why must all the gears in the chain have the same mesh angle?
Because they wont function correctly otherwise
What is a idler gear?
The gear in between the drive and driven gears
What is a intermediate gear?
It just like an idler gear but it has its own shaft
What is a lay-shaft?
A term used to describe a shaft that supports an idler or intermediate gear
What is a step-up drive?
When a gear train has a rotational speed output higher than the input
What is a step-down drive?
When a gear train has a rotational speed output lower than the input
What is a gear train?
A series of gears
What is a compound gear?
A gear that has more than on driving face
Where is a planetary reduction gear train mostly used?
In a aircraft propeller engine
What are toothed wheel gears?
It’s a shaft with multiple gears on to be able t select the gear ratio you desire
What are driving-key-type gears?
When a load of gears are set on two shafts that are constantly engaged and a spring loaded key selects the ratio it desires
What is a infinitely variable rotational speed?
A machine that allows you to pick any rotational speed you desire within its speed range
What are friction gears?
The driving friction wheel is movable so the rotational speed is infinitely variable
What is a cone pulley drive?
A device that is infinitely variable by adjusting the pulleys to move the belt resulting in different speed
If an aircraft doesn’t have fly-by-wire then what is its primary transmission component?
Cables
What forces can cables transmit?
Pulling
What forces can push rods transmit?
Push and pull
If you adjust a push rod what must you check for?
To see threads in the witness hole
