Week 1) Gears, Pulleys, Sprockets, Bearings Week 2) Motors & Controls FIRST Robotics 101 Week 1) Gears, Pulleys, Sprockets, Bearings Week 2) Motors & Controls Week 3) Pneumatics Week 4) Materials & Fasteners Week 5) Drivetrain and Framing Options Week 6) Arm & Winch Options Week 7) Team Building

Why do we need Gears and Pulleys? Why do we have gears? Why do we have pulleys? Easy Work Can Tow or Push Heavy Objects! Wow.. How Easy…Keep On Moving Titanic! Safety Glasses Geek Easy Work Can Lift Heavy Objects! Safety Glasses Nothing To It! Geek Muscles on a Geek? Come On!

Gears, Pulleys, Sprockets, Chains, & Tracks Spur Gears 1:1 Direction –X=Y (Opposite) X Gear Y Gear Teeth X Gear X Pitch Diameter Speed=> X=Y Speed Ratio=> X Pitch Diameter/Y Pitch Diameter X Teeth/YTeeth=1 YPitch Diameter Y Gear X Teeth=30 Y Teeth=30

Gears Speed=> X=(1.875)Y Speed Ratio=> Torque Ratio=> XPitchDiameter/.533*YPitchDiameter= 1/(16/30) = 1.875 X Teeth/YTeeth=>30/16=> Y=1.875X Torque Ratio=> Y= X/1.875 Efficiency Spur Gear Approximately 95% X Gear X Pitch Diameter X Teeth=30 Y Teeth=16 Y Pitch Diameter

Multiple Stage Gearing (Gearbox Design) Top View Motor Out In d=3x d=3x d=x d=x d=x Ratio Gear #1=> 3:1 Ratio Gear #2=> 3:1

Test Direction= In direction = Out direction Speed=> =Output = Input/(3 *3) = Input/9 Speed Ratio=> 9:1 Torque Ratio=> Output 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)?

Answers Answer #1: 5400/9= 600RPM/60 10 revs per second Answer #2: 2ft-lbs*9= 18 ft-lbs* 0.71= 12.78 N-m

Gear Types Bevel (90 deg Angle) Internal (Planetary) Rack and Pinion (Linear Motion) Spur (Normal) Higher Pitch= More Teeth Larger Face Width=More Force Must Match Pressure Angle

FIRST Rules: Rules ANY GEAR ANY TYPE ANY MANUFACTURER (except last years Robot) Plastic (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) Local Supplier: Buffalo Bearing Small Parts 1175 Military Road www.smallparts.com Kenmore, NY 716-874-1720

Pulleys Speed=> Y=4X Speed Ratio=> 12’’ 3’’ Torque Ratio=> (The only difference is the belt [connection method]) Speed=> Y=4X Speed Ratio=> 12/3XDiameter/YDiameter=4 Torque Ratio=> Y= X/4 Efficiency Pulley Approximately 90% 12’’ 3’’ Y Pulley X Pulley

Pulley Belts & Uses Timing Belt V-Belt Combination Timing & V-Belt -Think Tracks -Think Ball Chute -Think Climbing Obstacles Problems: Slipping Belts Come Off easily (No Sideways Torque) Tensioners Required Combination Timing & V-Belt

FIRST Rules: Sprockets Pulley Rules ANY PULLEY ANY TYPE ANY MANUFACTURER (except last years Robot) Sprockets (The only difference is the belt [connection method]) -Chain (Sprocket) instead of Belts (Pulley) instead of Teeth, (Gears) Plastic, Steel, ……

Sprockets ¼” Sprockets ¼’’ Chain ½ the weight 925lbs breaking Plastic Chain Stretches/ Steel is the Way to GO! ¼” Sprockets ¼’’ Chain ½ the weight 925lbs breaking Force. What a Steal!!! ¼” Pitch is harder to get but you meet your robot’s weight Lean and Mean! Nylon Sprockets Crack/ Steel is the Way to GO! Bicycle Chain

Bearings Problem! Grinding Heat After a While Loose Fit- Wobbly Bearings What Are They?? Problem! Grinding Heat After a While Loose Fit- Wobbly

Bearing Types Bearing Type 1: Softer Material like Bronze or Aluminum Shaft Bearing Type 1: Softer Material like Bronze or Aluminum Type 2: Ball Bearing Type 3: Roller Bearing

Bearing Types Solid Bronze Steel Balls Steel Cylinderical Rollers Sintered Bronze Bearing with optional oil Impregnation Ball Bearings Needle Roller Bearings Solid Bronze Steel Balls Steel Cylinderical Rollers Clutch One Direction Also Available

Pillow Block Bearings Self Aligning Two usually need per wheel This is used by the drivetrain: Self Aligning Two usually need per wheel One on each side of wheel Lighter weight pillow blocks have less life and need to be replaced.