Warlocks 8/5/05 TMU FIRST Robotics 101 u Week 1) Gears, Pulleys, Sprockets, Bearings u Week 2) Motors & Controls u Week 3) Pneumatics u Week 4) Materials & Fasteners u Week 5) Drivetrain and Framing Options u Week 6) Arm & Winch Options u Week 7) Team Building

Warlocks 8/5/05 TMU Drivetrain for Geeks u Geektrain Eat my Dust! Wheels Motor Steering Transmission

Warlocks 8/5/05 TMU What is a Drivetrain? u A “Drivetrain” has several major components: –Wheels or Tracks –Motor or Engine –Transmission –Steering –Linkage u A Robot needs a robust drivetrain to : –Move Fast. (Transmission/Wheels) –Push other robots out of the way. (Wheels/Transmission) –Precisely control where it is so that it can perform tasks. (Steering/Wheel/Transmission/Motor) –Needs power. (Motor) –Needs different speeds or variable speeds. (Controls/Transmission) –Turn on a dime. (Wheels/Transmission/Motor)

Warlocks 8/5/05 TMU Drivetrain Definition u The Drivetrain is a system of individual components working together to a achieve the desired function. Each component may contain many individual piece parts. Each system contains many components. –Components: Wheel, Gearbox, Motor, Linkage. –Piece Parts: Tread, Gears, Motor Coil, Sprockets, and Chains. u Several systems put together with each providing a function, build a robot. –Drivetrain System –Control System »Robot Interface/Software »Operator Interface –Manipulator System #1 –Manipulator System #2

Warlocks 8/5/05 TMU Drivetrain Top View u Layout Wheel Motor Gearbox Linkages/Gears Motor Gearbox Linkages/Gears Note: This is only one Robot System. Movement Traction Drives Wheels Speed Power Rotational Power (Torque) Direction Steering Turns Speed Into Torque Can Allow Multiple Speeds and Torques

Warlocks 8/5/05 TMU Linkage u Linkage Wheel Motor Gearbox Linkages/Gears Motor Gearbox 2” Diameter 1” Diameter Chains: Transfer Power To Wheels Sprocket Ratio: 2:1 Means Torque From Motor Increased By 2X. Speed from Motor is Reduced By 2X (½). Efficiency of power transfer is 90%.

Warlocks 8/5/05 TMU Gearbox Function u Gearbox Wheel Motor Gearbox 16:1 Sprocket Ratio: 16:1 Means Torque From Motor Increased By 16X. Speed from Motor is Reduced By 16X. Efficiency of power transfer is 95%. I am not going into gearbox design in this course. Ask after class. Let me just say it can be intense! But it is worth knowing! Gearbox Function: Convert Speed To Torque!

Warlocks 8/5/05 TMU Four CIM Motors u Motors Wheel Motor Gearbox Linkages/Gears Motor Gearbox Per Motor: (1) Slightly Loaded Speed= 4800 RPM (Cruising Speed) (2) Max Power Torque= 0.89 ft-lbs At 2655RPM. (Ramming Speed) (3) Max Torque = ft-lbs (Butting/Pushing Speed)

Warlocks 8/5/05 TMU Speed Calculation Speed= 4800/16 (Gearbox) =300 RPM at Sprockets 300 RPM/ 2 (Spockets) = 150 RPM at Wheels If there are 8” diameter wheels then: Circumference= 8*( )= inches =2.09 feet per revolution. 150 Rev/Min* 2.09ft/rev= feet/min = 5.23 feet/sec (5.23 feet/sec / 5280 ft/mile) * 3600 Sec/Hour= 3.59 miles/hour

Warlocks 8/5/05 TMU Torque Calculation Torque= ft-lbs X 16 (Gearbox) X 2 (Spockets) = ft-lbs/ motor X 4 Motors = ft-lbs (X.9 X.95) = ft-lbs Efficiency Max Power => 114 ft-lbs. X.9 X.95 = 97.5 ft-lbs (This is more like what you will see!) Question: Could a robot tow a Saturn on a Flat Surface?

Warlocks 8/5/05 TMU u Answer: Yes- I have Pictures ! Ugh! I’m towed By a Robot Into the Pits Robot Geektrain

Warlocks 8/5/05 TMU Robot Towing Car

Warlocks 8/5/05 TMU Billy’s Stats u Statistics on Last Years Robot “Billy” u Speed=> 4800/16= 300RPM X 30/16= RPM X.95 X.95X.90=457RPM 457RPM X 7 x PI /60= ft/sec Cover the field in 3 seconds. Ultra fast! u Torque=> 0.89 X4 = 3.56 ft-lbs* 16 = ft-lbs ft-lbs * 16/30 *.95 *95*.90 = ft-lbs “Billy could not push squat!” u Stall => ft-lbs u Billy placed 16th out of 1000 teams; Billy’s objective was to be ultra fast to place the last tetra on the goal on the other side of the field to take away a row. Obviously, it worked for that game! Torque & Force Calculator

Warlocks 8/5/05 TMU Braces, Nuts, & Bolts u Framing Options Braces Add Strength but take weight. Bolts connect pieces together. -Take Weight -Require Constant Retightening -Are They Really Needed? Typically: 4-5 Lbs can be taken out of frame by eliminating screws/bolts/braces

Warlocks 8/5/05 TMU The “Hole” Robot u Framing Options By holing everything out which takes days, you may get back 1.5 to 2.5 lbs

Warlocks 8/5/05 TMU News Flash: “2 Layer Frame Adds Weight” u Two Layer Base 2 layer frames add strength but require additional weight up 2.25X as much weight as a single layer! 1X.25X 2.25X

Warlocks 8/5/05 TMU New Invention: Lightweight Robot Frames u Ya know, we could just start with a lightweight robot frame. LWRF Inc.! I’m going to make millions Welded or Riveted Frame Bent Polycarbonate/Revitted Aluminum