7:12 Transmissions Flashcards
Overload wear (gears)
Occurs when the metal has been removed from the gear surface by its sliding action.
Heavy contact squeezes out the lube causing micro welds to form.
Resembles burrs, ripples or ridges on the tooth edge.
Pitting and spawling (gears)
Caused by thin oil films and high temps.
Chunks of metal flake away, flakes or chips damage other teeth.
Cracking + Breakage
Caused by a failure in the heat treatment process or improper machining during manufacturing.
Cracks are often very fine and not visible until the gear has been in service for some time
Interference wear (gears)
Misalignment of teeth.
Heavy contact is caused in small areas.
Abrasive wear (gears)
Caused by scratching and scoring, severity is dependant on the size of particles.
List the types of wear in gears.
Over load wear.
Pitting and spawling.
Cracking and breakage.
Interference wear
Abrasive wear.
What is Prussian blue used for
Examining the tooth contact pattern in gears.
What is backlash tolerance
The allowable amount of backlash
What is backlash variation
The difference between min and max.
Backlash in a gear train
Lock one end of the gear train.
Measure the limits of movement at the other end of the gear train.
Can use a dti or a feeler gauge
Elongation/deflection on a chain
Ranges 1.5%-3% when the chain is loaded.
Primary inspection of chains and sprockets
Ensure the chain passes smoothly over the sprocket.
Secondary inspection of chains and sprockets
Inspection for wear which requires a load applied.
Worn contours on chains
Replace when 5% worn.
Worm and peg mechanism
Rarely used on aircraft due to excessive backlash which causes localised wear.
