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The Art of LEGO Design
Michael Rosenblatt
September 19, 2000
Sources• The Art of LEGO Design, by Fred G.
Martin
• General Robotics 1999
• LEGO kit instructions
• My own experience
Goals:
• Build better robots– Minimize mechanical breakdowns– Build robots that are easy to control– Encourage good design strategy– Strive for elegant, clever solutions
• Know your materials
Know your Materials
• Quick facts:– Plastic bricks since 1949 (wooden blocks prior)– On average, 2100 different parts each year– Manufacturing tolerance: 1/1000 of an inch– Number of ways of combining six 8-stud bricks:
102,981,500– Widely used by scientists and engineers as a rapid
prototyping tool
Geometry
• 1-stud brick dimensions: exactly 5/16” x 5/16” x 3/8” (excluding stud height 1/16”),
• This is the base geometry for all LEGO components
• Three plates = 1 brick in height
Structure
• Common pitfall when trying to increase mechanical robustness:
Structure
• The right way:
Structure
• The right way:
Connector pegs
• Black pegs are tight-fitting for locking bricks together.
• Grey pegs turn smoothly in bricks for making a pivot
Structure
• Don’t do’s:– LEGO bricks HATE duct tape– LEGO bricks HATE hot glue and epoxy– Super glue also.
• You never need adhesives to build reliable LEGO structure
Help!!!
Drivetrain• LEGO Gears
8T
16T
24T
40T
24TCrown
??T Worm Bevel
Worm Gears• Pull one tooth per revolution
1
2
3
4• Result is a 24:1 gearbox• Not back driveable!
Motors
• 9V Gear Motor
• ~ 150 mA
• 300 RPM (no load)
• Internal gear reduction
Motors• 9V Micro Motor
• 20-30 RPM
• Internal two stage orbital gearbox (wow!)
Mounting Motors
Note Bulge under motor
Mounting Motors• Add a gear:
Mounting Motors• Use special 2x1 stud plate with “wing”
Build for good control• Slow vs. fast
• Gear backlash
Wires• Take pride in your wires!!!
• Wire management: use zip ties!!
Design Strategy• Incremental
– Test components parts as you build them• Drivetrain
• sensors, sensor mounting
• Structure
• Don’t be afraid to redesign
• Keep it simple– Easy to get excited
Design Strategy• Drivetrain driven
• Chassis/structure driven
• Modular?
Testing
• Don’t wait until you have a final robot to test– Interaction of systems – Work division (work concurrently)
• Develop test methods
• Don’t stop at first good result, test for repeatability
Philosophy
• Have fun
• Be creative, unique
• Strive for cool solutions, that work!
• Aesthetics: it’s fun to make beautiful robots!