Transmissions And Control Cables Flashcards
What is the purpose of transmission cables?
Change direction of control run is achieved by chain wheels and pulleys
Where are transmission cables found?
Control column installation
Aileron and elevator controls
Trim control systems
What are chains classified by?
Pitch
Roller diameter
Width between inner plates
What is fitted inside each roller to allow chain articulation around the sprocket?
Bush assembly
What is used to change the angle of the chain?
Bi-planer block
What are chain drives?
Where used?
Non-slip power transmission with a large gap between gears
Low friction
Smooth running
Used in engines
What should the number of chains on chain wheels be on roller chains?
No smaller than 12 teeth
What should chain wheels be?
Noise?
No smaller than 17 teeth
Virtually silent
What is trim control?
Power transmission achieved by chain drive
Tensioned by a chain tightener
Safety covers used to prevent separation
Every second link is an irreversible link
What are couplings used for?
To connect two shafts together
Three types of couplings?
Solid couplings
Moveable and Disconnectable couplings
Safety couplings
Which coupling is best known?
Sleeve coupling
What are Solid couplings?
Two cast iron sleeve fixed to the shaft ends by screws
Adjusting springs added if contact pressure is not high enough to transfer torque
What are Disk couplings?
Two disks fitted to the shaft ends by screws
Balancing achieved by a cylindrical insertion or a centre plate
What are Moveable couplings?
Used if shafts are not exactly aligned or if position of shaft changes during operation changes
Extension couplings allow small longitudinal movement
Types of gears
Drive gear - input gear
Driven gear - output gear
Can gain mechanical advantage (tooth ratio)
What is toothed wheel gear?
Transfer rotational movement at low speeds without any slip, operate in oil bath to reduce noise, need to be protected against contamination and to prevent accidents
What are Spur gears?
Straight tooth gears internal or external teeth
What is an external spur gear?
Used for change of speed, shafts lie parallel
What is an internal spur gear?
Pinion (smallest)
Spur (larger)
Gears rotate in the same direction, space saving
What is the most common gear?
Spur gears
What are Helical gears?
Noise?
Transmit drive between parallel shafts
Produce axial load on respective bearings
Very quiet
What are Rack and Pinion gears?
Convert rotation motion into linear motion
What are worm gears?
Helically cut gear on an input shaft driving a spur gear - mounted wheel on output shaft
Difference between worm gears and bevel gears?
Worm gives larger “step down”
What are Bevel gears?
Transmit drives between shafts having intersecting axes
May be found on engines
What should the angle of teeth be on herringbone?
Why?
No larger than 20 degrees
To avoid excess axial force
What is Backlash?
Clearance between gear teeth and point of mesh
What indicates excessive backlash?
Worn teeth
What is Idler gear?
Interposed between drive and driven shaft
What is Pinion?
Smaller of two mating gears
What is lay-shaft?
Shaft which supports idle gear
What are stepped pulley drives?
Single pulley drive - only as many rotational speeds as belt pulley has stages
Multiple pulley drive - two three-stage pulleys in series, produce 9 rotational speeds
What are the two types of Toothed gears?
Caster swivel wheel gears
Driving key type transmissions
What are toothed gears?
Engage and reach rotational speeds by sideways movement
Several gears arranged in series
Not suitable on drive machines for precision work
Usually only change gears during start-up or run-down
Different types of Infinitely Variable Rotational Speeds
Friction gears
Cone pulley drives
What are friction gears?
Driving friction wheel is moveable so the rotational speed of the driven friction disk is infinitely variable
What are cone pulley drives?
Suitable for transmission of smaller forces at high rotational speeds
What are Push Rods?
Transmit push/pull forces
What are Quadrants?
Forces transferred via cable quadrants
What are Rotary Selectors?
Transmit swinging or rotary movements
What is Step-up drive?
Provides higher speeds compared to the input
What is step-down drive?
Provides output drive of lower speeds compared to input
What are reduction gears?
Arrangement by which an input speed can be lowered to a slower output speed with same or more torque
Advantages of Control Cables?
Weight saving over mechanical actuators
Can be routed anywhere via pulleys and guides
What do Control Cables consist of?
Tensile strength minimum 1200 N/mm^2
Breaking elongation 2-7%
How are Control Cables made?
Wires twisted into strands
Strands twisted into cables
How are cables tensioned?
Cable tensiometer
Large aircraft have complex auto tensioning systems
Small aircraft have tension set at a compromised setting
What are Cable Terminals?
Ball and Double Shank Ball and Single Shank Long Threaded Stud End Short Threaded Stud End Fork End Eye End
What are Fairleads?
Guides to prevent contact with structure
What are Pressure Seals?
Through pressure bulkhead
Sealed with grease - prevents air loss
What are Pulleys?
Direction change
Guard pin prevents pulleys from falling off wheel
What are Cable Turnbuckles?
Attach cable ends and facilitate cable tensioning Left Hand and Right Hand threads
Rotate barrel/body
Never lubricate
Safety clip locking or wire locking
What are Flexible Remote Control Systems?
Manually operated from flight deck
Operating trim tabs, brake control valves, engine controls, etc
Can be bent to pass through structures
Two Cable and Conduit methods?
Teleflex
Bowden
What is Teleflex?
Pushes and pulls
Tension wire with either left or right helix winding
Engaging with gear teeth on control wheels
Three types of Teleflex?
DS 23/2 - left hand helix winding - 3/16” in diameter
DS 380 - right hand helix
DS 169330 - exact same as DS 23/2 but used in hot areas
What is a Single Entry Unit?
For Teleflex
Limited to 270 degrees travel
Minimum of 40 degrees at all times
What is a Double Entry Unit?
For Teleflex
Greater travel
Emerges at either 90, 120, or 180 degrees travel
What is a Spent Travel Tube?
Spare cable emerging from a double entry unit
What is an Anti-torsion tube?
Prevents cable from rotating during operation
What is a straight lead unit?
Not suited to heavy loads
What is a Junction Box?
Used to reverse the direction of travel of the control cable
Branch on run of cable to operate two components
What is a Sliding End Fitting?
Guide tubes terminating in a fork, eye, ball joint, internal or external threaded fitting
Cable is attached by either a special collet attachment or a lock spring and plug
What is the end fitting for a sliding end fitting?
Joint consists of a ball and socket connection inside a housing attached to the end of the rigid conduit
What is a Distributor Box?
Cables to Teleflex to screw jacks
Rotary to linear for trim tabs in conjunction with a torsion drive
Two conduit connectors?
Nipple type connectors
Clamp connector
What are Quick Break Units?
Various types
Facilitate removal of components without disturbing control
What are Bowden Controls?
Pull only Light loads only Returns via a spring Non-corrodible Steel Close coil wire Cotton braid Waterproof coating Prevent fraying - fit end caps (Bicycle brakes)
Three types of End Fittings on Bowden Controls?
Spherical
Trunnion
Plain
What are Adjustment Stops?
Hexagonal headed screws drilled to allow cable to pass through
Protective caps on screws
Stop fitted to remote end of cable - mounted in a tee barrel
Three types of connectors?
Cable connector
Control connector
Junction box
What is a cable connector?
Used to join different lengths of cable
Two cables only
Cannot be used where conduit is fitted
What is a control connector?
For joining two Bowden controls
What is a Junction Box?
Used where two components are controlled by a single control or vice versa
