gearing fundamentals Flashcards
what are two types of gear drives?
open gear drives and enclosed gear drives
what are open gear drives ?
gears that are exposed to the outside environment
whaat are enclosed gear drives?
gear drives contained with in a gearbox with lubrication supply
can be either oil or grease lubricated
what is a gear set?
matched pair of gears manufactured together
what is a gear train?
when two or more gear mesh or work together
what is a pinion?
when two gears that have different number of gears mesh or work together
what is a crown gear?
in beval and hypoid gear sets there are two mating gears
smaller one is a pinion
larger one is a ring gear (crown)
what is the drive gear power in and power out
power in is the input gear train that causes mating gears to turn
- power out is the output gear train that the drive gear forces to turn
what is direct drive?
when the input speed of the gearbox is the same as the output speed
what is a speed reducer?
a gear train with a slower output speed that input speed occurs when a small gear drives a larger gear out put has more torque but less speed
what is a speed increaser
a gear train with a faster output speed that input speed occurs when a large gear drives a smaller gear less torque but same speed
one issue with over hung gears?
tend to have more shaft deflection under heavy loads because of a bearing support on only one side of the gear
what are straddle mounted gears
are mounted between two bearings ,stronger and less shaft deflection than overhung gears
what are internal gears ?
have teeth on the inside diameter of the gear , operate more smoothly than external gears , more tooth contact
what is a compound gear train?
have 3 or more shafts and four or more gears,
useful where a higher reduction or speed increase is important
substantial gear reductions can be achieved by using what ?
compound gear trains
what is end play?
when the gear shaft is allowed to move axially
what is axis of rotation?
centre line around which a gear or parts revolve
usually centreline of shaft
what is a floating gear or shaft ?
lists when one gear os shaft is allowed to move axially to its best position
what gears can be right hand or left hand gears?
helix angle
what is chordal thickness?
the thickness of the gear tooth the pitch of circle indicated tooth strength
what does an involute do ?
makes meshing with the mating gear quieter and smoother, has radius across the flank and the face of the tooth
what is one method in checking contact pattern?
use Prussian blue mixed with oil or red lead
where should back lash be checked?
the point at closest engagement
what is diametral pitch?
is the number of teeth on the gear divided by the pitch diameter
lower the number bigger the gear teeth
what is AGMA stand for
american gear manufactures
what is binding and what causes it
check with out a load
binding is where tight spots are felt
lack of backlash
incorrect center distances
gear center out of tolerance
bent shafts
thermal expansion
what is a pressure angle?
angle of the gear tooth, gear trains have pressure angles of 14.5 deg to 20 deg
true or false ?
meshing gears must have the same pressure angle?
true
what are two basic gear teeth profiles?and what are the differences
involute and straight
involute has a slight curve on the face of the gear
-straight have straight faces and are very noisy not suitable for high speed or high power applications unless speeds are very low
when an even amount of gears mesh with each other the last gear rotates ?
first gear turns clockwise last gear turn counter clock wise
if an odd number of gears mesh with each other the last one rotates ?
same direction as the first gear
an internal gear set has both gears moving in ?
the same direction
paraelle shafts are?
equal distances apart on two diff planes
spur gears
helical gears
double helical gears
herring bone gerars
what do idlers do?
they change the direction of rotation or keep it the same
-can connect two gears with a c-c distance that is greater than the gears
spur gears can be used in 3 basic arrangements ?
external
internal
rack and pinon
what are intersecting shafts ?
shafts are at 90 deg to each other but on the same plane
beval gears
mitre gears
what is crossing over at 90 deg?
worm gears
hypoid gears
helical gears
spur gears develop no axial thrust unless they are misaligned because?
there teeth are straight
can contain many types of material from metallic to non metallic
single helical gears have the teeth cut at an angle to the shaft axis true or false
true
what are the common angle on a helical gear ?
7-12deg
what is an advantage of of using a double helical gear?
axial thrust is canceled by the opposite row of teeth
where are herringbone gears reccomened ?
for high speed applications and heavy loads
must be mounted on shafts that are parallel
where are bevel gears used ?
used on shafts that have intersecting axes most common bevel gear intersects at 90 deg
true or false bevel gears develop axial thrust loads and radial thrust loads?
true require a bearing that can handle both types of load
why are spiral bevel gears stronger than straight bevel gears ?
they have more teeth in contact at the same time ,manufactured in pairs and to mesh must be of opposite hands
do zerol bevel gears have axial thrust like spiral bell gears ?
no and they are smoother and quieter than straight cut bevel gears
whats the difference between a throated and non throated worm
non throated worm is shaped like a cyclinder
- throated worm is shaped like a hour glass
a simple planetary gear set consists of three parts?
a sun gear
a carrier with a planet gears mounted to it
- a ring gear
The pinion gear is usually the smaller gear in the set, true or false
true
Gears are positive transmission devices that are used were there can be no slippage true or false
true
Most gears are made to the standards set by the AGMA true or false
true
The flank of the gear tooth is located in that addendum true or false
true
I drive using helical gears can have the gear set up so they are overhung true or false
true
In a compound gear system, there can be six and four shafts, true or false
true
A gear set that has a 20° pressure angle is stronger than a gear set with a 14 1/2° pressure angle
true
It is best to measure the backlash of a gear sat at the pitch circle, true or false
true
A gear with the diametral pitch of four has very small teeth, true or false
true
A gear train has 15 gears meshing together with the input gear rotation in the clockwise direction. The output gear should turn in counter clockwise direction, true or false.
false odd number of gears last gear turns the same as the first gear
Helical gears of parallel shops must use gears of the opposite hand, true or false
true
A gearbox has a 10 to 1 reduction driven by a 1 hp electric motor at 1750 RPM. The output from the gearbox is 10 HP at a speed of about 175 hp.
false , hp cannot be increased in a gear set
Double helical gears are good for high speeds and heavy loads, true or false
true
A spur gear set that intersects at 90° must be of the same hand true or false
false spur gears are straight cut and do not intersect
Herringbone, gears, or light duty drivers, true or false
false they are heavy duty
Spiral bevel gears look very similar to hypoid gear’s true or false
true
Hypoid gear’s have high, sliding action and require an EP additive in the oil true or false
true
The heel of a hypoid or spiral bevel gear is near the inner circle true or false
false
Worm gear have a lot of sliding action, true or false
true
Warm gears, or less efficient than most other types of gears, true or false
true
higher friction heat and wear means greater energy loss
Double throated worm and warm will Gear still have a maximum gear tooth contact true or false
true
