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MACHINE ELEMENTS > Gears > Flashcards

Gears Flashcards

1
Q

defines the average number of teeth in contact at any one time

A

contact ratio

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2
Q

A minimum contact ratio for smooth operation

A

1.2

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3
Q

Most spur gearsets will have contact ratios between

A

1.4 and 2.

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4
Q

A disadvantage of unequal-addendum tooth forms is an

A

increase in sliding velocity at the tooth tip.

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5
Q

Interference (and undercutting caused by manufacturing tools) can be prevented simply by

A

avoiding gears with too few teeth

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6
Q

As the number of teeth is reduced for a fixed diameter gear,

A

the teeth must become larger.

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7
Q

Severe undercutting will promote

A

promote early tooth failure.

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8
Q

arc length along the pitch circle circumference measured from a point on one tooth to the same point on the next.

A

circular pitch

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9
Q

defines the tooth size.

A

circular pitch

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10
Q

tooth is measured along the axis of the gear.

A

face width

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11
Q

tooth thickness is measured at the

A

pitch circle,

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12
Q

tooth space width is slightly larger

A

tooth thickness.

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13
Q

Tooth space width - tooth thickness

A

backlash

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14
Q

dedendum is slightly larger

A

addendum

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15
Q

tip of one mating tooth

A

(addendum circle)

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16
Q

bottom of the tooth space

A

(dedendum circle).

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17
Q

tooth height is defined by the

A

addendum

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18
Q

tooth height is defined by the

A

addendum and dedendum

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19
Q

(AGMA)

A

American Gear Manufacturers Association

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20
Q

They define a spectrum of quality numbers and tolerances ranging from

A

lowest (3) to the highest precision (16).

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21
Q

backlash can cause potentially

A

“hunting”

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22
Q

back-to-back on the same shaft that can be rotated slightly at assembly with respect to one another,

A

antibacklash gears

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23
Q

Another factor affected by changing center distance is

A

backlash.

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24
Q

clearance between mating teeth measured at the pitch circle

A

Backlash

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25
Q

As the center distance increases

A

pressure angle and vice versa

26
Q

The common normal is

A

still tangent to the two base circles and still goes through the pitch point.

27
Q

The velocity ratio is unchanged despite the shift in center distance.

A

Unchanged

28
Q

center distance errors ____ the velocity ratio.

A

Do not affect

29
Q

the gear tooth form is not an involute, then an error in center distance will violate the fundamental law, and there will be variation, or

A

“ripple,”

30
Q

There will also be an ideal center distance ( CD ) that will give us the nominal pitch diameters for which the gears were designed. U

A

center distance

31
Q

defined as the angle between the axis of transmission or line of action ( common normal)

A

pressure angle

32
Q

direction of velocity at the pitch point

A

pressure angle

33
Q

distance along the pitch circle within the mesh

A

arc of action

34
Q

subtended by these points and the line of centers

A

subtended by these points and the line of centers

35
Q

The arc of action on both pinion and gear pitch circles

A

The arc of action on both pinion and gear pitch circles

36
Q

The distance along the line of action between these points within the mesh i

A

length of action,

37
Q

common normal of the tooth profiles, at all contact points within the mesh

A

pitch point

38
Q

The ratio of the driving gear radius to the driven gear radius

A

remains constant as the teeth move into and out of mesh.

39
Q

curves at the contact point,

A

common tangent

40
Q

perpendicular to the common tangent.

A

common normal

41
Q

common normal, which is also the

A

axis of transmission,

42
Q

The amount of tooth that sticks out

A

addendum,

43
Q

The cylinders from which the strings are unwrapp

A

base circles

44
Q

base circles are necessarily

A

necessarily smaller than the pitch circles,

45
Q

The string is always

A

angent to the cylinder.

46
Q

The center of curvature of the involute is always at the

A

the point of tangency of the string with the cylinder.

47
Q

The contact point between the cylinders lies on the line of center

A

pitch point.

48
Q

reciprocal of the angular velocity ratio (mV)

A

torque ratio (mT)

49
Q

equal to the ratio of the radius of the input gear to that of the output gear.

A

angular velocity ratio (mV)

50
Q

equal to the ratio of the radius of the input gear to that of the output gear.

A

pinion and gear

51
Q

are ones in which the teeth are parallel to the axis of the gear. This

A

SPUR GEARS

52
Q

are ones in which the teeth are at a helix angle, Ψ, with respect to the axis of the gear

A

HELICAL GEARS

53
Q

They run quieter than spur gears because of the smoother and more gradual contact between their angled surfaces as the teeth come into mesh.

A

HELICAL GEARS

54
Q

are formed by joining two helical gears of identical pitch and diameter but of opposite hand on the same shaft. These

A

HERRINGBONE GEARS

55
Q

which has only one tooth wrapped continuously around its circumference a number of times, analogous to a screw thread.

A

Worm

56
Q

means that the worm gear teeth are wrapped around the worm.

A

Single enveloping

57
Q

resulting in an hourglass-shaped worm.

A

Double enveloping

58
Q

based on the rolling centrodes of a Grashof double-crank fourbar linkage.

A

Noncircular Gears

59
Q

If the teeth are angled with respect to the axis,

A

SPIRAL BEVEL GEARS

60
Q

If the teeth are angled with respect to the axis,

A

a spiral bevel gear

61
Q

bevel gears are based on

A

rolling cones

62
Q

rotary to linear motion conversion or vice versa. It

A

Rack and Pinion

MACHINE ELEMENTS (4 decks)

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