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!