Gears Flashcards
________________ gears have curved angled teeth that transmit motion between parallel shafts.
Helical
Name five types of gear designs.
(4 H's, 2 B's, W, S) Helical Herringbone Hypoid Double helical Bevel Spiral bevel Worm Spur
____________ gears have straight cut teeth and transmit motion between parallel shafts.
Spur
______ gears have cone shaped shafts and transmit motion between shafts at right angles.
Bevel or spiral bevel
Helical gears are not preferred to spur gears because they create_______.
Thrust
Name the main advantage that double helical (or herringbone) gears have over single helical gears.
They eliminate thrust load.
In general, worm gears should be lubricated with oils of ______ viscosity than spur and helical gears. Why?
Higher viscosity
A worm gear set has a greater degree of sliding motion.
Name the type of gear that is able to product the largest decrease in speed and the largest increase in torque.
Worm gear
What type of gear typically uses bronze as its material?
Worm gears (It is actually the gear that is driven by the worm)
What are four functions of gears?
Transmit power
Change direction
Change speed
Change torque
Name five gear failure modes.
Tooth breakage, surface fatigue ( spalling ), wear and scoring ( galling ), plastic flow ( deformation ), Also, wiping, scuffing, abrasive wear, overload, Hertzian fatigue, brittle fracture, ductile fracture, rolling, bruising, peening, pitting, scratching, cutting gouging, denting, seizing, flacking, feather edging, brinelling, rippling, fish scaling, ridging, tip-to-root interference, adhesion, corrosion, fretting, cavitation, electrical discharge damage, polishing, burnishing, welding, smearing.
What are three factors (or conditions) that affect gear life?
(LETS) Load Environment Temperature Speed
What destructive forces lead to plastic flow in gears?
Heavy loads and impact loading
What generally causes gear tooth breakage due to fatigue?
Many repetitions of bending stresses
The gear tooth dedendum (below the pitch line) will generally show initial pitting. True or False.
True
Name four methods that gear manufacturers use to improve surface durability (decrease pitting).
Increase hardness
increase face width
Increase pinion pitch diameter
Improve geometry
Name two immediate effects of overfilling a gearbox.
Heat
Foam
The fluid may overflow
If you wanted to use only two gear lubricants for an entire plant, what two would you pick and where would they be used?
Synthetic EP 460 for heavily loaded, slow speed and worm gears, Synthetic EP 220 for higher speed, lighter loads, parallel shafts
What type of lubricant should be used in a gear box that contains a hypoid gear set?
API GL-5 extreme pressure gear oil
Name eight gear oil additives.
(FORCE COPS FVI)
Friction Modifiers Compounding Foam inhibitor
Oxidation Inhibitors Oiliness or Polar VI Improvers
Rust Inhibitors Pour paint depressant
Corrosion Inhibitors Solid – Graphite Moly
Extreme Pressure
Why are EP additives not particularly effective with steel in contact with metals such as brass, bronze, babbitt, or aluminum?
Contact of a ferrous and non-ferrous metal may not generate temperatures high enough to activate the EP additive.
EP additives may be corrosive to yellow metals at high temperature.
Sliding motion is better lubricated with a PAO of fatty material.
Name three types of open gear lubricants.
Asphaltic
Soap base
Solvent cutback
Soap base with tackifiers and solid fillers such as moly and/or graphite.
What are some of the effects of using gear oil whose viscosity is too low?
Increase in noise
Vibration
Temperature
Wear
What form of scoring on gears is worse galling or scuffing?
Galling
Many tribologists relate galling and scuffing as the same.
