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FIRST MOTORS

FIRST MOTORS. ETC. by Joe Johnson. Introduction. Joseph Michael Johnson, Ph.D., P.E. Delphi Automotive Systems Interior Systems Division Advanced Development Group Electro-Mechanical Dept. Designs Clever Mechanisms for $ 4 patents issued, ~20 pending 5th year as FIRST team leader.

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FIRST MOTORS

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  1. FIRST MOTORS ETC. by Joe Johnson

  2. Introduction • Joseph Michael Johnson, Ph.D., P.E. • Delphi Automotive Systems • Interior Systems Division • Advanced Development Group • Electro-Mechanical Dept. • Designs Clever Mechanisms for $ • 4 patents issued, ~20 pending • 5th year as FIRST team leader

  3. Introduction (cont.) • “The Ooga Man” • “He can walk on his hands!”

  4. Comparing Motors • MOTOR CHARACTERISTICS • STALL TORQUE • STALL CURRENT • FREE SPEED • FREE CURRENT • NOTE: all the above are proportional to voltage

  5. Comparing Motors • See Excel Spread Sheet

  6. Formulas, Etc. • Unit conversions of interest • 1lbs = 4.45 N • 1 inch = 0.0254 meters • 1 in-lbs = 0.11 N-m • 1 RPM = 60 Rev / Hour = 0.1 Rad / Sec • 1 mile = 5280 X 12 inches = 63,000 inches • Torque = Force X Radius • Power = Force (N) X Velocity (m/s) • Power = Torque (N-m) X Angular Velocity (Rad/Sec) • Electrical Power = Voltage X Current

  7. Arm Example • 10 pound ball • 5ft, 20 pound Arm • Question: Can this motor lift that arm & ball? • Answer: Yes, of course… ...given time!

  8. Power Example • Suppose you want to lift your robot 6 inches in 2 seconds. • What motors are candidates? • Power Required: • 130 lbs = 580 N, 6 inches = .15 meters • 580 N * .15 m / 2 seconds = 43 Watts • So… Bosch Drill, Fisher-Price, Delphi Sliding Door, and Globe motors all are candidates • Marginal motors must operate near Peak Power range and have an efficient drive train to work -- loose 30% & no dice!

  9. Arm Example 2 • Lifting an Arm requires 1800 in-lbs of torque (30 lbs 5 ft out) • We want to rotate the arm 90 degrees in 3 seconds • Power Required: • 90 deg / 3 sec = 5 RPM = 0.5 Rad/sec • 1800 in-lbs = 200 N-m • 200 N-m X 0.5 Rad/Sec = 100 Watts • Serious Business this ball lifting!

  10. The Importance of Counter Balance • Make your motors work to move UP and DOWN • Don’t make your motors use energy just to stay still • Use a Gas Spring or Latex Tubing to help your motors on the way up

  11. Arm Example 3 • Same As Example 2 BUT… ...We now add two 60 lbs Gas Springs pushing at 6 inches • Effective torque to lift arm • (1800 in-lbs) - (2X60lbsX6in) = 1100 in-lbs • Power Required: • 90 deg / 3 sec = 5 RPM = 0.5 Rad/sec • 1100 in-lbs = 120 N-m • 120 N-m X 0.5 Rad/Sec = 60 Watts • Much Reduced!

  12. Motors With Internal Thermal Protection • Delphi Window Motor (Mfg.: Valeo) • Delphi Seat Motor (Mfg.: Keyang) • Delphi Sliding Door Motor (Mfg.: Taigene) • It is especially important not to run these motors near stall for the entire match • Mixed blessing: Other motors can become toasters • Consider buying “Cool in a Can”

  13. Efficiency Matters, ALOT • Spur Gears: 90-95% • Worm Gear: 10-60% • Nut on a Tread (not ball nut): 10-60% • Twist Cables: 30-70% • Chain: 85-95% • Cable: 0-98% • Rack & Gear 50-80%

  14. Motor Allocation • Many motors in the kit • But… you must use them wisely • Most teams (wisely) use Bosch drill motors as main drive • Some teams have been successful using F-P or Taigene motors • Delphi Tape Drive Window Lift Mechanism: useful and efficient • Lear Seat Adjuster Mechanism: easy, robust, but not very efficient

  15. Divide up Scarce Resources • Small Parts Inc. $ • Motors, bearings, actuators, etc. • Space • Weight

  16. Divide up your team • Robot • Crate & Cart • T-shirts • Trading Buttons • Public Relations • Chairman’s Award (book, video) • Animation • Fund Raising • Travel • Cheer Leading • Celebration Planning • Practice Field Building

  17. FIRST Accounting • Keep an accurate bill of materials from day 1 • Refine as build phase progresses • $425 -- lots of confusion • Joe’s method of explanation: AFTER you finish your robot, pretend you are now going to build another one You must be able to buy everything you need from SPI for less than $425

  18. Get SOMETHING Rolling NOW • Buy last year’s drills motors and transmissions (Marsh Power Tools) • Buy last year’s batteries & charger & connectors • Buy two VICTORS from Innovation FIRST • Buy some wheels from Skyway • Buy some .25 pitch chain & sprockets from Small Parts Inc. • Either wait for your FIRST controller or build one from hobbyist parts (brave souls will make one using a STAMP2).

  19. Some Friendly Advice • How FAST should a robot go? Joe’s Answer: <8MPH & >1MPH • Watch your weight (Rookie Mistake #1) • Use the kit -- additional hardware list is full of great stuff • Do Something Well -- less in often more • Watch the calendar -- six weeks is too short

  20. Some Friendly Advice (cont.) • Watch the web -- usfirst.org & chiefdelphi.com • Get a copy of last year’s rules & all updates -- read them • NOTHING gives as much bang for the buck as driver time • Get a good picture of your robot BEFORE you ship it • Plan a Celebration Event NOW -- too tired after EPCOT

  21. Some Friendly Advice (cont.) • Get several colors of paint pens -- very useful • Use numbered tape (McMaster page 1498) for Wiring, Motors, Victors, Relays, Joysticks, etc. • Organize your tools before you get to Regional • Make “Strategic Spares” • Shipping = “Out of your hands” FIRST is flexible -- call them 1st

  22. Some Friendly Advice (cont.) • Hard stops are… …well, HARD • Use end of travel switches • Plan wiring/switches from Day 1 • Mount Joysticks, Radio, etc. to an easily carried board • Consider using “Official Thread” everywhere possible (e.g. 10-24) • Get SEVERAL Small Parts Catalogs NOW! (smallparts.com)

  23. Some Friendly Advice (cont.) • McMaster-Carr is your best friend (McMaster.com) • Buy Tie Wraps NOW (McMaster page 620 SMALL, MED, LARGE) • Buy “Velcro” NOW (McMaster page 2874 Mushroom Head type - reg & extra sticky) • Find a Wire EDM source -- Beg them to donates a few gears burned from 1/4” steel plates

  24. Some Friendly Advice (cont.) • Wire EDM may not be so needed in 2000 • Alternate Gear, Sprocket Sources • Stock Drive Products (sdp-si.com) • W.M. Berg (wmberg.com) • Boston Gear (bostgear.com) • Rush Gears (rushgears.com) • Martin Sprocket & Gear (martinsprocket.com) • Brown (dpbrown.com) • PIC Design (pic-design.com) *** Sell Mates to Bosch Drill Motor Pinion!!! *** • Motion Industries (motionindustries.com)

  25. Some Friendly Advice (cont.) • Travel is a BIG job • Pick Drivers early • Pick Coaches early • Drivers & Coaches must work well together • Consider using 2 motors if one is too slow or too weak

  26. Some Friendly Advice (cont.) • Model Behavior you want your kids to copy: • Don’t Cheat (even if nobody will ever catch you) • Don’t Disrespect Ref’s, Opponents, Alliance Partners, Fellow Teammates,...

  27. The MOST important thing to keep in mind... • You have a family...

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