6.9- Transmissions Flashcards
How is power transmission achieved from engine to flying controls?
Through the use of belts, cables, control chains, chain wheels, pulleys and levers.
What other components may you find in transmissions?
Shafts, pull and push rods, cranks, eccentrics, threads, friction wheels, hydraulics and compressed air.
What do chains provide?
Strong, flexible and positive connections.
Where are chains generally used?
Where it becomes necessary to change the direction of controls runs in systems where considerable is exerted.
What 3 systems might chains be used in?
Control columns
Aileron and elevator controls
Trim controls
How are chains classed?
Pitch, roller diameter and width between plates.
What are some benefits of roller chains?
Low frictional loss
low maintenance.
What purpose does a chain cover serve?
Prevents jumping of the chain creating separation between chain and teeth.
What type of couplings do you get?
Solid
moveable and disconnectable
safety
What are the two best known solid couplings?
Sleeve couplings and disk couplings.
Where is a moveable coupling used?
If the shafts are not in alignment or if the position changes during operation?
What class of coupling is an elastic coupling?
Moveable.
Cross links such as universal joints are used to transfer what and what’s their benefit?
Stronger forces
They require no maintenance.
If a drive gear has 50 and the driven gear has 100 teeth what is the ratio, the mechanical advantage and what does that mean?
1:2
MA is 2
Which means the power required to drive the driven gar is halved.
What does a toothed wheel gear provide?
Transfer rotational movement at low speed without slip.
Where are external spur gears used?
When a change of speed is required and the shafts lie parallel to each other.
What are helical gears used for?
Used to transmit drive between parallel shafts.
What is an advantage of helical gears?
They have more teeth in mesh to provide a larger contact area.
What is rack and pinion?
Linear actuator. The pinion is the circle and the rack the bar.
What are bevel gears used for?
Used to transmit drive between shafts with intercepting axis.
What’s the benefit of herringbone over helical gears?
The axial forces are eliminated, therefore they are used for large forces.
What is a gear ratio?
Direct measure of the ratio of rotational speeds.
If the driven gear is smaller than the drive gear will it turn faster or slower?
Faster.
How do you work out gear ratio?
Driven gear teeth divided by drive gear teeth.