HET 4 GEARING Flashcards
GEARING PRINCIPLES 190401C
What are components of a gear tooth?
Face, Flank, Heel and Toe
Is the concave side or the convex side the drive side?
Convex side is a drive side
The larger end of a gear is the?
a) heel
b) toe
c) face
d) flank
Heel
What is special about the root fillet area?
Its rounded, to give strength
When the is off the throttle and is in a coasting moment, what happens to the drive and driven side of a gear?
The opposite side becomes the driven, concave is drive and convex is driven
What three circles are measurable in on a gear?
Root
Pitch
Outside
What needs to be found before the circular gear pitch can be determined?
Pitch circle
If the gears in mesh have the same circular gear tooth pitch, what does it achieve?
Greatest strength
The clearance between the root and tooth tip of two gears is there for what reason?
To provide a space for lubrication
Why are gears not installed in tight contact?
No room for expansion during operation
What tool is used to measure backlash?
Dial indicator
When gears have run together for a long time what can happen?
change in tooth profile/shape, gears have worn into eachother
What types of timing are possible with gears?
Hunting, Non-Hunting and Partial Non-Hunting
Why are timing marks important in a non-hunting gear set?
The timing marks must line up - proper timing - longer service life
What type of timing design would a gear set be if the ratio is 5:1?
Non-hunting
What type of timing design would a gear set be if the ratio is 8.5:1?
Partial non-hunting
What type of timing design would a gear set be if the ratio is 3.89:1?
Hunting
Describe hunting gear sets?
No specific wear pattern is created, every tooth in one gear will touch every tooth in the other gear, no timing
If a few teeth on one gear constantly mesh with only a few teeth on another gear, the gears are timed or not?
Timed - non or partial non hunting
Which type of gear timing has the most distinctive wear pattern?
Non-hunting
When two external gears are in mesh what is produced?
A reverse
What is the speed difference between input and output gears when they are identical size?
No speed differences
Why is path-of-power important to understand when looking at gears?
Helps determine gear ratios, troubleshoot faults
Gear rations are written in relation to drive and driven gears, in a 1:2 ration which is driven and which is drive?
1 is drive and 2 is driven
To find the gear ration what is divided or multiplied?
Driven is divided by drive
Driven over Drive
Driven (24) ÷ Drive (12)
If a gear starts to show blue colouring what could be the problem?
No backlash - No lube - Heat
Crankshaft and Camshaft timing is considered which design?
a) hunting
b) non-hunting
c) partial non-hunting
Non-Hunting, specific timing
If a drive gear rotates twice and the driven gear rotates once, what type of drive is it?
Reduction
What does an idler do between to external gears?
Changes output gear direction of rotation
True or False
Idlers are used to change speed and torque?
False - only direction of rotation
Are gear ratios added together or multiplied?
The gear ratios are multiplied against eachother
Without an idler what three conditions can two gears run in?
Direct drive, Reduction and Overdrive
Is it more likely for the pinion gear to be the drive member or the crown gear?
Pinion gear is usually the drive gear
What are three types of external gears?
Spur/straight cut, helical cut, double helical cut
True or False
Internal gears mesh with other internal gears?
False
What thrust loads are produced by single helical gears?
Axial thrust
Why are double helical gears great?
No/little axial thrust
What is a negative feature of a herringbone gear?
Cost to manufacture
What is commonly the drive (input) in a simple planetary?
Sun
Tapered roller bearings can handle what types of thrust loads?
Axial and radial thrust loads
What are the four basic components of a simple planetary?
Sun, Planets, Carrier and Ring Gear
Direct drive can result if two components are held, what other way can direct drive be created?
two components being driven at same RPM
Hypoid gears have the pinion above or below the center line of the crown gear?
Below the center line
In what set up are pinion gears above the center line of the crown gear?
Amboi gears
In a basic spiral bevel gear set where is the pinion gear in relation to the crown gear center line?
Centered with the center line
Rack and pinion gears do what with rotary motion?
Rotary motion is turned into linear motion
What situations are worm gears good for?
High Torque loads
Is it common to see worm and worm wheel gear sets on a high speed on-highway trucks?
No
unless it has a winch!
What is the purpose of an amboid gear set up?
Driveline is higher - off road
Does a hypoid gear set up have more or less tooth contact during meshing, when compared to a pinion that is centered on the crown gear?
More tooth contact
True or False
Hypoid angle gears are used in LOW torque situations?
False, High torque loads
Angle gears can have a maximum angle of?
90°
A reactionary member can also be referred to as a?
Held member
To have a planetary operate, what conditions must the components be in?
one member is a DRIVE
one member is DRIVEN
one member is HELD
If none of the members of a planetary are held what condition is created?
Neutral
Why is extreme pressure lubricant used in hypoid gear sets?
Sliding contact and pressure between gear teeth during meshing process is very high
Do hypoid gear sets have the same load handing abilities as an amboid gear set?
Yes
When the carrier is held what is created?
a reverse
