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Gears, Pulleys, Sprockets, and Bearings Gears, Pulleys, Sprockets, and Bearings

Gears, Pulleys, Sprockets, and Bearings - PowerPoint Presentation

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Uploaded On 2016-07-18

Gears, Pulleys, Sprockets, and Bearings - PPT Presentation

Information about power transmission and uses for each type Robotics 101 Why do we need Gears and Pulleys Why do we have gears Why do we have pulleys Geek Easy Work Can Tow or Push Heavy Objects ID: 409878

torque teeth ratio gear teeth torque gear ratio speed bearings gears bearing pitch types diameter force pulleys motor 875 rpmx input direction

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Slide1

Gears, Pulleys, Sprockets, and Bearings

Information about power transmission and uses for each type.

Robotics 101Slide2

Why do we need Gears and Pulleys?

Why do we have gears?

Why do we have pulleys?

Geek

Easy Work Can

Tow or Push

Heavy Objects!

Easy Work Can

Lift

Heavy Objects!

Nothing To It!

Geek

Wow, How Easy…Keep On Moving Titanic!

Muscles on a Geek?

Come On!Slide3

Torque, moment, or moment of force,

is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. Mathematically, torque is defined as the cross product of the lever-arm distance and force, which tends to produce rotation.

Torque = Radius X Force

Or Force = Torque / Radius

What is Torque

?Slide4

Gears

Spur Gears 1:1

Direction -X=Y (Opposite)

X Gear

Y Gear

X Teeth=30

Y Teeth=30

Speed- X=Y

Speed Ratio-

X Pitch Diameter/Y Pitch Diameter= 1

X Teeth/Y Teeth= 1

Teeth

X Gear

X Pitch Diameter

Y Gear

Y Pitch

DiameterSlide5

Gears

Speed Ratio- Compare either ratio of # of teeth or diameters as both have same proportion:

# of teeth/min = (X teeth * RPMx) = (Y teeth * RPMy)

=

X teeth

=

RPMy = 30

=1.875 Y teeth RPMx 16

Or RPMx/RPMy = 1/1.875 = .533 = 16/30X PitchDiameter = 1.875 * Y PitchDiameter

X Teeth/Y Teeth= 30/16- Y=1.875X Speed-

RPMy=(1.875)RPMx or RPMx=(.533)RPMyTorque Ratio- Ty/Tx=.533 (Note: It is the inverse of the speed ratio)Ty= Tx/1.875 = Tx(.533) Efficiency of Spur Gears: Approximately 95%

X Gear

X Pitch Diameter

X Teeth=30

Y Teeth=16

Y Pitch Diameter

Τ

x

Τ

ySlide6

Multiple Stage Gearing

Top View

d=x

d=x

d=3x

d=3x

Ratio Gear #1- 3:1

Ratio Gear #2- 3:1

Motor

d=x

Out

InSlide7

Test

Direction- In direction = Out direction

Speed- Output = Input/(3*3) = Input/9

Speed Ratio- 9:1

Torque Ratio- 1:9Output Torque= Input Torque X 9

If the motor input RPM (revolutions per minute) is 5400 and input torque is 2 ft.*lbs.1) What is the output speed in revolutions per second (60 seconds in 1 minute)?

2) What is the output torque in Newton*meters if 1 N-m=0.71ft-lbs.? Slide8

Answers

Answer #1: 5400/9= 600RPM/60= 10 revs per second

Answer #2: 2ft-lbs*9= 18 ft.-lbs.* 0.71= 12.78 N-mSlide9

Gear Types

Bevel (90° Angle)

Internal (Planetary)

Rack and Pinion (Linear Motion)

Spur (Normal)

For all Gears:

Higher Pitch= More Teeth

Larger Face Width= More Force

Must Match Pressure AngleSlide10

Gear Rules and Types

FIRST Rules:

Any gear

Any type

Any manufacturerPlastic (Lighter, Smaller Load)Brass (A Little Lighter (mainly due to small width), Good Load)

Steel (Heavy, Excellent Load, will need to trim down gear on lathe for weight)Slide11

Pulleys

The only difference is the belt connection method

12’’

3’’

Speed- Y= 4X

Speed Ratio-

XDiameter

=

12

= 4:1

YDiameter 3

Torque Ratio-

Y= X/4

Efficiency of Pulleys:

Approximately 90%

X Pulley

Y PulleySlide12

Pulley Belts & Uses

Pulley Belts

V-Belt

Timing Belt

Uses:

-Ball Chute (2012)

-Drivetrain (2014, 2015)

-Climbing Obstacles

Problems:

Slipping

Belts coming off pulleys

(No Sideways Torque)Slide13

Chain and Sprockets

Chain and SprocketsThe only difference is the connection method

I

nstead of Belts (Pulley)

Instead of Teeth (Gears)Types of ChainPlastic

Light loads, breaks easilySteelHeavy loads (drivetrain)Types of SprocketsNylonLight loadsAluminum

Heavy loads (drivetrain)

Plastic Chain Stretches-

Steel is the way to GO!

Nylon Sprockets Crack- Aluminum is the way to GO!Slide14

Chain and Sprockets

Bicycle ChainSlide15

Bearings

Bearings- What Are They?

Problem!Slide16

Bearing Types

Type 1: Softer Material like Bronze or Aluminum

Type 2: Ball Bearing

Type 3: Roller Bearing

ShaftSlide17

Bearing Types

Sintered Bronze Bearing with optional oil impregnation

Ball Bearings

Needle Roller Bearings

Clutch

One Direction

Also Available

Steel Balls

Steel

Cylindrical

Rollers

Can be sealed or unsealedSlide18

Bearing Types

Pillow Block

Bearings

Self

AligningUsed when you need some compliance in alignment.Slide19

Issues to be aware of with bearings

Misalignment

of bearing systems can over-restrict them, causing higher friction and unnecessary force on systems. Be careful of over-restricting things that want to be able to move.

Dirt, debris, and chips

can get into bearings, especially open bearings: it increases friction and resistance. (Therefore protect bearing services when machining on or near the robot)

Exceeding the recommended load for a bearing can shorten or even end its life and lead to need for replacement- or may add friction to the system causing overload on motors causing them to fail.Motors have internal bearings you don’t see, so avoid excessive loads on shafts- beware of pounding on motor shaft ends (installing or removing items on motor shafts). Use proper techniques to avoid damaging internal shaft supports in the motor, by not applying excessive loads.

Don’t stand or lean on the robot! No matter how sturdy it “seems”- we have had bent wheel shafts, and gotten frames out of square. In trying to make weight we lighten up areas where possible, but the robot may be less robust.