7.12 Flashcards
What is gear failure usually caused by ?
Backlash and/or poor lubrication.
What’s overload wear ?
Occurs when the metal has been removed from the tooth by its sliding action.
( squeezes out lubricant causing micro-welds )
( forms burrs on teeth )
What is pitting and spalling on a gear and how is it caused ?
- Caused by thin oil films and high temperatures.
- fine crack caused by hardening
What can cause cracking on a gear ?
Failure in the heat treatment.
( cracks isn’t visible until the gear has been in service for a long time )
What’s abrasion wear caused by ?
Scratching and scoring on the teeth.
( severity depends on size of particles carried with the lubricant. )
Explain Prussian blue ?
Blue dye placed on the leading edge of the teeth of the driving gear which gets transferred to the driven gear leaving a contact pattern which determines weather the Correct shimming or assembly relationship can be setup.
Whats the 4 sides to a gear ?
Heel end
Toe end
Drive side
Coast side
What’s the purpose of backlash ?
To prevent gears from jamming and making contact on both sides.
What does a small amount of backlash allow ?
Lubricant to enter and accommodates for differential expansion.
What is backlash ?
Play between mating tooth surfaces
How can you measure the backlash in a gear train ?
DTI
What does the percentage limit of elongation range from ?
1.5% - 3%
Whats the main role of a sprocket ?
To change rotary motion into linear or vice versa.
( in long runs, a pro kept can be used as a support for the chain in the form of a idler sprocket )
How can cracking and splitting be caused on a belt ?
Due to it slipping which can also cause heat build up.
Where is a screw jack usually used ?
Trailing edge flaps.
