FIRST MOTORS ETC. by Joe Johnson

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

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

Comparing Motors n MOTOR CHARACTERISTICS u STALL TORQUE u STALL CURRENT u FREE SPEED u FREE CURRENT u NOTE: all the above are proportional to voltage

Comparing Motors n See Excel Spread Sheet

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

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

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

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

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

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

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

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

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

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

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

FIRST Accounting n Keep an accurate bill of materials from day 1 n Refine as build phase progresses n $ lots of confusion n 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

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

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

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

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

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

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

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

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

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

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