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
what is the cause of cracked plates?
loading beyond the chains dynamic capacity
fractured plates are caused by what?
high overload of the chain
what are cracked plates caused by?
static pressure at press fit plus severe corrosion or acid exposure
what are enlarged holes caused by ?
high overload
what is a rusted chain caused by?
moisture exposure or poor lube
in the case of an emergency, what can be used to extend the landing gear?
sprocket and chain system
what is the main role of a sprocket ?
rotory to linear or vice versa
what does the sprocket act as in long chain runs?
acts as support
what is the load capacity of a belt compared to a chai drive?
much smaller
what are the benefits to a belt drive system?
-shock resistant
- quieter
-smoother
-do not need to lube
are belts life’s limited?
yes they are
what must a belt be inspected for?
-wear and degradation
-cracking or splitting
-chipping or fraying
what defects require the replacement of the belt?
-cracking and splitting
-shipping and fraying
how can the tension be tested on a belt?
by pushing on an unsupported section
why is the work and peg mechanism not used in aircraft?
excessive backlash
the worm and nut mechanism is used in aircraft, how is actuation of the mechanism generated?
turn shaft to drive nut or nut to drive shaft
what is the recirculating ball mechanism referred to as ?
ball screw actuator
how does the nut move on a recirculating ball mechanism’s shaft ?
shaft turns making the balls circulate. nut moves as long as it’s fixed so it doesn’t rotate.
screw jacks are primarily used where?
flap drive systems
what are the primary concerns when inspecting a screw jack?
lubrication and backlash
what should be checked for in a push pull rod?
straightness, wear in the ends, security of check nuts and end fittings
where are push pull rods used?
aircraft aileron and trim tab
what are bell cranks used for ?
transmit a force or motion or permit a change in direction
