Transmissions Flashcards
What is transmissions achieved by
belts, cables, control chains, chainwheels, pulleys and levers.
Chains.
provide strong, flexible and positive connections and are generally used wherever it becomes necessary to change the direction of control runs in systems where considerable force is exerted.
Control column installation
Where can a change in direction be found
- Control column installations
- Aileron and elevator controls
- Trim control systems
How are chains classified
their pitch, roller diameter and width between plates.
Chain drives
for non-slip power transmission with large spaces between axles when cogwheels are not available to decrease the size of the spaces.
Roller chains and gear chains
Low frictions
Smooth running
Roller chains
Don’t require much maintance
Work with any disturbance
Gear chains
cogged lugs which engage into the gaps between the teeth of the chain wheel. They are virtually silent in operation. The number of teeth of the chain wheels should not be smaller than 17 with regard to wear.
Chain classification
Pitch
Width between inner plates
Diameter of rollers
Change of direction of a chain by 90 degrees is achieved by
Biplaner lock
Trim control
cogged lugs which engage into the gaps between the teeth of the chain wheel. They are virtually silent in operation. The number of teeth of the chain wheels should not be smaller than 17 with regard to wear.
Number of theeth on a roller chain
No less than 12
Number of theeth on a gear chain
No less than 17
Irreversible chain link
To stop chain to be fitted wrong way round
Heart shape
What is a couplings
Couplings are used to connect two shafts with each other. They are classed as:
• Solid couplings
• Movable and disconnectable couplings
• Safety couplings
Solid couplings
Rigid connection
Sleeve ans disk coupling
Sleeve consists of 2 iron cast sleeve fixed into shaft end. If the contact pressure is not high enough to transfer the torque, adjusting springs are added.
Disk coupling two dicks fitted to shaft end, cylindrical insertion or a centre plate to ensure two disks are balanced
Movable couplings
comprise expansion couplings, hinge couplings and elastic couplings. They are used if the shafts are not in alignment or if the position of the shafts change during operation.
Cross links
such as universal joints, are suitable to transfer stronger forces, such as in cars. If the journals of the journal cross assembly run in pin bearings, these links need no maintenance.
Extension coupling
allow a small longitudinal movement of one shaft in relation to the other
Claw coupling
Hinge coupling
comprise cross-links, dry-disc joints and ball- and socket- joints. They are used where the direction of the axes of the shafts linked to the couplings change in a certain, limited angle.
Drive gear
Imput
Driven gear
Output
Mechanical adavanbged
Number of teeth on drive and driven gear
Ratio of them
Driven over drive
Toothed wheel gear
Transfer rotational movement at low speeds with out slip
Operate in oil Bath to reduce noise
Need to be protected against contamination and axidents
Spur gear
straight toothed gear wheels with the teeth formed externally or internally
External when a change of speed is required shafts lie parallel to each other
Helical gear
Transmission drive between parallel shafts
Produce axial load on represpective bearings
Rack and pinion
Converts rotation motion to kinda reflect
Worm gear
The worm and wheel gear set consists of a helically-cut worm gear on an input shaft, driving a spur gear-mounted wheel, on an output shaft. The axes of
the two shafts cross at 90° and are in different planes
Gives a large step down between the driver and driven shaft
Bevel gear
transmit the drive between shafts which have intersecting axes
Found in engines main dive shalf of engine to drive accessory
Hearing bone gear
Helical gear teeth create a force that acts in an axial direction. This force
has to be picked up by axial bearings. To avoid excessive axial force, the slanting angle of the teeth should not be larger than 20 degrees to avoid excess axiel strength
Transfer large forces
Backlash
Gap between teeth at point of contact
Idler gear
Support gear between the driver and the driven , extra support
Pinion
Smaller of 2 mating gears
Lay shaft
Supports a idlier or intermittent gear
Step up drive
Provides high speed output compared to imput
Step down drive
Provides high speed imput composted to outout
Gear trains
2 or more gears on a series of shafts
Reduction gears
Reduces speed going from gear to gear
Accessory drive unit
Helical gear teeth create a force that acts in an axial direction. This force
has to be picked up by axial bearings. To avoid excessive axial force, the slanting angle of the teeth should not be larger than 20 degrees.
Planetary (Epicyclic) Reduction Gear Train
Used to reduce the speed of an aircraft engine’s output shaft to a more acceptable speed for its propeller. It has the advantage of putting the output shaft
(the propeller), in line with the input shaft (the engine crankshaft)
Sun driving
Stepped pulls drive
With a single-pulley drive, only as many rotational speeds can be reached as the belt pulleys have stages.
Multiple pulls drive
Two three stage pulls in series produce 9 rotational speeds
Needs to be switched on for it to work
Toothed wheel gears
- Caster swivel wheel gears
- Driving-key-type transmission
The wheels of variable gears are engaged and reach the desired rotational speed by moving them sideways. If many rotational speeds are required by a machine tool, several gears are arranged in series
Not suitable for precision work
Switch off to change gear
Infinity variable rotational speeds
The wheels of variable gears are engaged and reach the desired rotational speed by moving them sideways. If many rotational speeds are required by a machine tool, several gears are arranged in series
Changed during operation
Driving key type gears
transmit small forces at low rotational speeds. The tightly-fitted toothed wheels on the driving shaft are constantly engaged to the loosely-adjusted wheels of the driven shaft.
Change gears during operation
Don’t need much speed
Cone pulley drive
transmission of smaller forces at high rotational speeds. The cone pulley pairs are axially movable. By adjusting the pulleys, the V-belt is forced to move more to the outside of one pulley and more to the middle of the other
Adjustment ratio of 10:1
Transmission Component Control Mechanism specification
- Safe
- Lightweight
- Movement free from play
Cables
Cables are the primary transmission components in airplanes without fly-by- wire systems. Versatile Free movement to play Weight saving Can only transmit pulling forces
Push rods
Used to operate rudders flaps
can transmit pulling and pushing forces.
Quadrants
Forces are transferred to cables via cable quadrants and the forces of the cables are also transmitted to push rods via cable quadrants
Rotator selector
Transmit Swinging or rotary movements
