Teacher/Mentor Institute
Robot Design and Construction Tips
Scott McEwen
September 15, 2012
Overview
Engineering Design Process
 Subsystems & System Integration
 Communication & Documentation
 Design Engineering & Math Examples
 Construction Tips

Materials
 Fabrication & Safety

September 15, 2012
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Engineering Design Process
Importance


Proven process for any design/build project
Every team is required to submit an
engineering notebook that documents the
process to design, build, and test your
robot
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Engineering Design Process
Elements
1.
2.
3.
4.
5.
Define the problem
Determine the design specifications
Develop numerous design alternatives
Choose the optimal design
Build and test the design
Ref: http://best.eng.auburn.edu/ -> Participants ->
Contest Information -> Team Resources -> Engineering
Topics
September 15, 2012
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1) Define the Problem

Read the Rules thoroughly at
www.bestinc.org
The Competition -> Current Game Rules
 Participants -> File Manager -> Public Files
 Participants -> Contest Information
 Password: r1bb0n

Inventory Consumable & Returnable Kits
 Research similar problems and designs

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2) Determine the Design Specs
Clear guidelines for creating viable designs:
 Goals


Score lots of low point items, then score high
point items
Requirements
Ability to ascend/descend quickly
 Ability to grab various game pieces


Constraints

Must fit in 24” cube and weigh <= 24 lbs
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3) Develop Numerous Design
Alternatives
Engineering design = creative process +
content knowledge from variety of
disciplines
 Brainstorming

Multiple Groups of 3-4? 1+ designs/student?
 Sketches, notes, logical & physical models


Scoring Tip: Brainstorming Approaches:
How well organized and productive was the
brainstorming approach used and documented?
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4) Choose the Optimal Design

Weigh and document pros & cons of each
design
Analysis of gaming strategies and design
elements to achieve goals
 Do we have the tools and skills to build it?


Scoring Tip: Analytical Evaluation of
Design Alternatives: Use of analytical and
mathematical skills in deciding upon and
implementing design alternatives
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5) Build and Test the Design
Invest adequate time and specificity prior
to this step
 Revisit prior design steps as needed
 Scoring Tip: Safety Training *and* safety
practices followed
 Scoring Tip: Support Documentation


Drawings, photos, test results, etc.
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Subsystems & System
Integration

Drive Platform
Ascend & descend
 Speed & position control


Articulated Arm and end effector (grapple)
Rotate left to right
 Extend up & down
 Extend in & out
 Grip efficiently


Programming
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Communication & Documentation
Communication Best Practices

Communication mediums
Traditional
 Social media
 SCRUM – Daily stand-up meetings
 Other

Resolving disagreements/conflicts
 What works for your team?

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Communication & Documentation
Engineering Notebook

Document the process used to design,
build, and test the robot.


Tell the story of your robot
Documentation is a critical aspect of the
Engineering Process. Provides:
Crucial record of the process
 Critical info between different groups
 Checklist against requirements
 Essential information for new people

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Communication & Documentation
Important Dates
Engineering Notebooks are due on
Practice Day (Saturday, Oct 20)
 Every team MUST submit an Engineering
Notebook
 If no notebook on Practice Day, your team
will NOT be able to compete on Game Day
 Notebooks will be returned on Game Day

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Design Engineering & Math
Examples – Torque

Dimensions and torque

Small Motor


Large Motor



http://content.vexrobotics.com/docs/276-1610-Drawing-Rev1A.pdf
http://content.vexrobotics.com/docs/276-1611-Drawing-Rev1A.pdf
Inch-pounds = amount of torque required to lift a 1
pound weight 1 that is 1 inch from axis of rotation
Computing torque: Torque = Force * Moment Arm


Torque = Weight (pounds) * moment arm (inches)
Total torque = Sum of (weights * moment arms)
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Design Engineering & Math
Examples – Torque
PVC Pipe @ 0.21 lb/ft
 Grapple @ 0.5 lb
 Waste Cargo Ball @ 0.4 lb

September 15, 2012
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Design Engineering & Math
Examples – Torque
Torque = Weight (pounds) * moment arm (inches)
PVC: (2 ft * 0.21 lb/ft) * 1 ft =
 Grapple: 0.5 lb * 2 ft =
 Ball: 0.4 lb * 2 ft =
 Combined: 0.42 + 1.0 + 0.8 =
September 15, 2012

0.42
1.00
0.80
2.22
ft-lb
ft-lb
ft-lb
ft-lbs
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Design Engineering & Math
Examples – Torque
2.22 ft-lbs = 26.64 in-lbs
 Large Motor torque = 23.53 in-lbs
 “Back to the drawing board”

September 15, 2012
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Design Engineering & Math
Examples – Motor Specs
Futaba S3003 servo
• Torque: 2.75 in-lb (44 oz-in)
• Gear Type: Plastic
BEST Small Motor
•
Torque: 9.49 in-lb (152 oz-in)
BEST Large Motor
•
Torque: 23.53 in-lb (376.48 oz-in)
September 15, 2012
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Design Engineering & Math
Examples – Potentiometer (Pot)







Definition. A Pot is an electrical device whose resistance is
adjustable. It can be used as an analog sensor to measure angular
position of a rotational component, such as a robot arm. The Cortex
can use the Pot’s output to control or limit some other component.
Input. Connect Pot’s shaft to a rotational axle or shaft. NOTE: the
POT’s total range of motion (i.e., rotation) is 300 degrees.
Output. Connect the Pot’s wiring to a Cortex analog input port.
Operation. As the resistance of the Pot changes, so does the voltage.
This varying voltage can be measured by the Cortex and is directly
proportional to the angular position of the Pot’s shaft.
Data sheet: http://www.bitechnologies.com/pdfs/p160.pdf
easyC example: https://sites.google.com/site/team3141rx/easyc/arm3
Wiring example:
http://www.education.rec.ri.cmu.edu/classes/cal_u/ar/toolbox/content/curriculum/robotics_systems/ho
me_brew/potentiometer/potentiometer.swf
September 15, 2012
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Construction Tips
Materials
 Fabrication & Safety

September 15, 2012
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Materials
Polypropylene Sheet
 Aluminum bar, rod, & sheet
 Steel all-thread rod
 Wood
 PVC pipe
 Electrical
 Fasteners
 Miscellaneous

September 15, 2012
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Fabrication & Safety
Club Workshop

Location & Hours



Cost:






Special RM BEST rate
Call 720-324-7222 for details
Tools


999 Vallejo Street, east of I-25 and north of 8th Ave
7 days/week, 9a to 11p M-F; 8a to 11p, Sat & Sun
Woodwork Shop, with CNC router
Machine Shop
Metal Shop
Classes
www.clubworkshop.com
September 15, 2012
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Fabrication & Safety
Cutting Plastic Sheet (video)
Wear eye protection & secure work
1.
Scribe and break – Sturdy knife

2.
3.
Jig saw – New blade, 10 teeth/inch
Band saw – ½-wide blade, 14 teeth/inch

4.
May cause melting
Circular saw – Carbide tip, triple-chip

5.
Good for 1/8” sheet
Plywood blade will cause melting
Table saw – 60-80 teeth, triple-chip, 1/8 to ½
inch blade exposed
September 15, 2012
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Fabrication & Safety
Cutting Aluminum Bar & Rod
Wear eye protection & secure work
 ½-inch Bar
Hacksaw: laborious and slow
 Jig saw: (see notes)
 Band saw: wood-cutting blade
 Horizontal band saw:

 straight
& safe
 Visit Club Workshop
September 15, 2012
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Fabrication & Safety
Cutting Aluminum Sheet

Tin Snips: laborious



Air or power shears
Sheet metal shear



Stop short of full cut to avoid
cut marks
Visit Club Workshop
For marking, use ultrafine
Sharpie
After cutting, dress edges
with file
September 15, 2012
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Fabrication & Safety
Bending Aluminum Sheet
•
•
•
Hand bender
Vise
Sheet metal brake
• Visit Club Workshop
September 15, 2012
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Fabrication & Safety
PVC and Wood

PVC
Hacksaw
 PVC cutter


Wood: Holes &
round parts
Drill
 Drill press
 Hole saw

September 15, 2012
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September 15, 2012
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Fabrication & Safety
Drill Press Speeds (rpm)
Wear eye protection & secure work
Bit Type
Plywood
& Pine
Acrylic
Aluminum
Steel
Twist, 1/16” to 3/16”
3000
2500
3000
3000
Twist, 1/4” to 3/8”
3000
2000
2500
1000
Twist, 7/16” to 5/8”
1500
1500
1500
600
Twist, 11/16” to 1”
750
NR
1000
350
Hole Saw, 1” to 2.5”
500
NR
250
NR
Spade bit w/ spurs, 3/8” to 1”
2000
500
NR
NR
Circle Cutter, 1.5” to 3”
500
250
NR
NR
Circle Cutter, 3.25 to 6”
250
250
NR
NR
Circle cutters: Drill 1st side, flip material over, finish on 2nd side
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Fabrication & Safety
Wear eye protection & secure work
 Center punch holes to prevent drill from
wandering

Clamp work
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Fabrication & Safety
Fasteners – Drill and Tap
•
•
•
•
Threads are cut inside a hole
using a tap
Match hole size (numbered drill
bit) to screw
Screws: size – threads/inch
Purchase drill/tap sets at Ace
Hardware
Machine
Screw
Drill Bit
Number
1/4”-20
8
#10-32
21
#8-32
29
September 15, 2012
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Fabrication & Safety
Electrical Components
Proper
connection of
electrical
components
Mount Cortex
for easy access
September 15, 2012
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Fabrication & Safety
Limit Switches
Mini Snap
September 15, 2012
SubMini Snap
Connect to digital port
Closed = “0”
Open = “1”
Page 33
Fabrication & Safety
VEX Motor Mounting Kit
• Specifically designed
to mount BEST
motors
• Flat, but designed to
be easily bent
September 15, 2012
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Fabrication & Safety
BEST References
http://best.eng.auburn.edu/b_game_rules.php
http://best.eng.auburn.edu/stored_procedures/folder-manager/


1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
2012 BEST Consumable Kit List
2012 BEST Returnable Kit List
BEST Large Motor Spec Sheet
BEST Small Motor Spec Sheet
BEST Generic Kit Usage Guide
3.X VEXnet Firmware Upgrade Utility Operating Instructions and Installation
Cortex Microcontroller and VEXnet Joystick User Guide
VEX Cortex Pin-out
Introduction to easyC & Cortex (Intelitek)
Google for PDF: “Tools, Tips and Materials” by David Kwast
September 15, 2012
Page 35
Club Workshop

Location & Hours



Cost:






Special RM BEST rate
Call 720-324-7222 for details
Tools


999 Vallejo Street, east of I-25 and north of 8th Ave
7 days/week, 9a to 11p M-F; 8a to 11p, Sat & Sun
Woodwork Shop, with CNC router
Machine Shop
Metal Shop
Classes
www.clubworkshop.com
September 15, 2012
Page 36