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IDIS 303 > Chapter 4 - Gears > Flashcards

Chapter 4 - Gears Flashcards

(65 cards)

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1
Q

Types of gears

A 
Spur
Helical
Bevel
Worm
Hypoid
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2
Q

Gears

A

Earliest form of power transmission.
Class one lever.
Generally speed reducers and torque increasers.
Transmit torque and speed to create motion by direct contact.

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3
Q

Driver Gear

A

Transmits the torque.

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4
Q

Terminology of a gear

A 
Pressure angle
Face width
Addendum
Dedendum
Circular pitch
Pitch circle
Pitch diameter
Outside diameter
Root diameter
Clearance
Whole depth
Center distance
Circular tooth thickness
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5
Q

Pressure angle

A

Angle between normal of the tooth and the tangent of the gear.

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6
Q

Face width

A

Length of a tooth running along the gear axis

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7
Q

Addendum

A

Difference between outside diameter and pitch circle.

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8
Q

Dedendum

A

Difference between pitch circle and root diameter.

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9
Q

Pitch Cylinder

A

Point of contact on tooth when gears mesh together and the tangent of each gear creates a straight line.

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10
Q

Pitch Circle

A

Circle around the gear that corresponds with all pitch cylinders.

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11
Q

Pitch Diameter

A

Diameter of the pitch circle.

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12
Q

Pinion

A

Smaller gear and usually the driver gear.

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13
Q

Clearance

A

Difference between addendum and dedendum of a tooth.

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14
Q

Full Depth of Teeth

A

Total depth of the tooth space.

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15
Q

Working depth of teeth

A

The max depth that a tooth penetrates into the tooth space of the mating gear.

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16
Q

Working Depth

A

Sum of addendums of two gears.

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17
Q

Space Width

A

Width of the space between teeth along the pitch circle.

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18
Q

Tooth Thickness

A

Thickness of a tooth along the pitch circle.

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19
Q

Backlash

A

Difference between the space width and tooth thickness.

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20
Q

Top Land

A

The surface of the top of the tooth.

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21
Q

Bottom Land

A

Surface between bottoms of teeth excluding fillets.

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22
Q

Flank

A

Surface between pitch circle and the bottomland including fillet.

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23
Q

Fillet

A

Curved portion of the tooth flank at the root circle.

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24
Q

Circular Pitch

A

Distance along the pitch circle from one point on a tooth the the corresponding spot on the next tooth.

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25
Diametrical Pitch or Module
Number of teeth per unit length of the pitch circle diameter in inches. Module is same but in mm.
25
Module
Ratio of pitch diameter to the number of teeth in mm.
26
``` 1 3/4 DP= 2 DP= 2 1/2= 3= 3 1/2= 4= 5= 6= 7= 8= 10= 12= 14= 16= 18= 20= ```
1.7952" Circular Pitch 1.5708" 1.2566" 1.0472" .8976" .7854" .6283" .5236" .4488" .3927" .3142" .2618" .2214" .1963" .1745" .1571"
26
Idler
Makes the shaft rotation of one gear to another in the same direction. Has no effect on torque or speed transmitted.
27
Open Gear Types by Shafts:
Parallel Shafts Intersecting Shafts Skew Shafts
27
Parallel Shaft Gears:
``` Spur Helical Double Helical Internal Rack and Pinion ```
27
Intersecting Shaft Gears:
Straight Bevel Gears Spiral Bevel Gears Zerol Bevel Gears Skew Tooth Gears
27
Skew Shaft Gears:
Crossed-helical Gears Worm gears Hypoid Gears
28
Spur Gear
Basic form of gear. Straight teeth parallel to axes and not subject to axial thrust. Moderate Speed, low cost, low maintenance. Most widely used gear type.
29
Spur Gear Coarse Type:
1-19 Diametrical Pitch
30
Spur Gear Fine type:
20+ Diametrical Pitch
31
Spur Gear Standard Teeth types:
14 1/2-deg coarse pitch 20-deg coarse pitch 20-deg fine pitch 25-deg coarse pitch
32
Helical Gears
``` Teeth are at an angle. Produce thrust load on both shafts. Carry more load, less vibration, higher speeds and quieter. Mating Gears have same helix angle. RH & LH to mesh. ```
33
Double Helical Gears
Pair of Helical gears secured together. Cancels axial or thrust force. Higher Speeds, less noise, less vibration.
34
Herringbone Gear
A Double Helical Gear with no groove in-between.
35
Internal Gear
Can be spur or helical type. Advantage is space constrain. Same direction of rotation.
36
Spur Rack and Pinion
Indefinite diameter. The rack is a straight rectangular bar with teeth. Converts rotary motion into linear motion or vise versa.
37
Bevel Gears
Axes usually at 90 deg but sometimes different. | Produce thrust load on both shafts.
38
Four types of bevel Gears:
``` Straight Spiral Zerol Skew Hypoid-non intersecting shafts ```
39
Straight Bevel Gear
Simplest and most common bevel gear. Teeth (if extended) come to a common point. Outermost point of teeth is the thickest. Don't need to be the same size.
40
Spiral Bevel Gear
Teeth are inclined and at an angle to the face of the bevel. Have overlapping teeth that result in less noise. Axial thrust exists. Used for a differential in an automobile.
41
Zerol Bevel Gear
Have curved teeth but have zero-degree spiral angles.)))) | High contact ratios, less noise and vibration, high efficiency (>97%).
42
Skew Tooth Gear
Gears are spiraled but teeth are not curved, teeth are cut at an angle to the centerline. Used for large diameters (>30" pitch diameters).
43
Crossed-Helical Gear
Shafts are at an angle and don't intersect. | Light loads, sliding action, must be lubed.
44
Worm Gear
Most popular gear configuration. Consist of threaded worm and a worm wheel. Worm slides along wheel teeth, and takes several rotations for one rotation of wheel. Worm always drives the wheel. CW or CCW. Low efficiency (50-90%)..
45
Types of Worm Gears:
Cylindrical worm meshing with a helical gear. Single-enveloping gear-wheel has curved teeth to partially wrap. Double-enveloping gear-worm and wheel are curved to wrap each other.
46
Hypoid Gear
Similar to spiral bevel gears but the shafts don't intersect.
47
Gear Trains
Multiple gears form together to make a gear train.
48
Gear Train Types:
``` Simple Gear Trains Compound Gear Trains Planetary Gear Trains Epicyclic Gear Trains Harmonic Gear Trains ```
49
Simple Gear Trains
All gears lie in the same planes.
50
Compound Gear Trains
Multiple gears on the same shaft.
51
Planetary Gear Trains
Sun Gear is the main driving gear. Planet gears around mounted around it.
52
Epicyclic Gear Trains
Direct competitor of planetary. | Very high gear ratios (100:1).
53
Harmonic Gear Trains
Gear ratios in order of 1000:1. | Rollars force flexible gear to contact the ring gear on opposite sides.
54
Speed Reducers Types:
Worm-Gear Speed Reducers Helical-Gear Speed Reducers Planetary Speed Reducers
55
Worm-Gear Speed Reducers
Low cost, low efficiency, very quiet. Up to 100:1. Single-reduction, Double-reduction(60-3600:1), Triple-reduction(-180,000:1).
56
Helical-Gear Speed Reducers
High efficiency, 1,2,3,or4 set of gears. Total reduction=multiple of each reduction.
57
Planetary Speed Reducers Types:
Single-Stage or Simple Planetary Reducers. | Differential Planetary Reducers.
58
Single-Stage or Simple Planetary Reducers
Consist of sun gear that drives three planetary gears. Planet carrier is surrounded by planet gears. Ratio=1+(Nring/Nsun) N=# teeth
59
Differential Planetary Reducers
Construction is same as simple planetary reducer except planetary gears are supported by a free-floating planet carrier which is free to rotate about the sun gear.
60
Factors in Reducer Selection
``` Load Ratings Service Factors Horse Power Torque Gear Ratio Overhang and bending loads ```

IDIS 303 (8 decks)

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