Module 7.12 Flashcards
when does overloading wear occur?
when metal has been removed due to a sliding action
what does heavy contact cause
squeezes out lubricant and causes microwelds to form
what does overload wear look like?
burrs on edges, ripples and ridges.
what is pitting and spalling caused by?
thin oil films or high temps
what can spalling cracks usually lead to?
chunks of metal flaking away, which can damage other teeth
what is cracking usually caused by?
failure in heat treatment process or improper machining
what is interference wear caused by?
misalignment of gears or incorrect mating of the teeth
where is heavy contact caused because of interference wear?
at teeth tips and roots
abrasion of the gear teeth is caused by what?
scratching or scoring
what affects the size of the abrasion marks?
size of particles in the lubricant
what is wear pattern
the print that one set of gear teeth leaves on another
how can the tooth contact pattern be established?
by using prussian blue a blue dyed paste
what is the purpose of backlash ?
prevents jamming and contact on both sides
what is backlash?
play between the teeth on the gears
what is the backlash variation?
difference between max and min backlash in a whole revolution of the larger of a mating pair of gears
how can backlash in a gear train be measured?
lock one end and measure limits of movements at the other with a DTI
what can affect the amount of backlash?
change change in centre distance
variance in tooth thickness
temperature ranges
what are the primary and secondary inspections of a chain?
primary: chain runs smoothly over sprocket
secondary: checks that require an applied load
in a secondary inspection, what should the elongation be?
1.5% to 3%
when should a chain be replaced from a worn contact?
when 5% worn
what causes pin galling and how can it be corrected?
inadequate lube -> reduce load or speed, proper chain lube
what are tight joints caused by?
dust and foreign objects caught in the joints
what must be done to a sprocket with hooked teeth
replace chain and the sprocket
what causes abnormal protrusions or turned pins
high loading and inadequate lubricant