1. 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

2. 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!

3. 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

4. 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

5. 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

6. 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)?

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

8. 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

9. 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
Kenmore, NY

10. 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

11. 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

12. 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, ……

13. 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

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

15. 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

16. 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

17. 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.