Getting Started With Great Ball Contraption

Why Listen to Me?

• Masters Degree in Engineering
• Soothing, melodic voice
• GBC Participant for 5+ years
• 15+ modules built

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What is a Ball Contraption?

• Device to move balls along
• Endless loop of Rube Goldberg style do-nothings
• Excellent source of ABS dust
• Educational combinations of simple machines into complex systems, ideally yielding a robust, aesthetically pleasing, fault-tolerant apparatus

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The Formal Standard

• 10 studs wide, 10 studs long, 10 bricks high input hopper
• Some way of moving balls into an output hopper
• Able to transport 1 ball/second
• Able to handle pulses of up to 30 balls
• Links:
• http://www.teamhassenplug.org/GBC/
• http://www.brickwiki.info/wiki/Great_ball_contraption
• http://greatballcontraption.com

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Here in Seattle

• Tend to run a little slower than 1 ball/second
• Pulses tend to be more like 5-10 balls, not 30
• We run sub-loops, so if a single module fails, the whole thing doesn’t crash
• Target a 10-high input hopper and a 12-high output hopper, making a testing jig easier

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One Motor to Rule Them All:

Common Power Standard

• Own one motor, want to build and run multiple modules
• Power Functions XL motor turns a shaft outside of any module
• A shaft runs the entire length of each module, allowing next module to attach; 3 bricks up, then a technic brick
• Include a 24-tooth gear with clutch in transmission; one jam doesn’t stop the line
• shaft is between 5 and 6 studs to left of hopper
• Counter-clockwise when looking downstream of ball flow
• RPM is max rpm of XL motor ~220 rpm

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Shared Power Standard

• Centered over 5-6 studs away from the hopper
• 1x2 technic brick resting on 2 bricks
• Use a slip gear on each module, so jams don’t stop the system
• Or define your own; the point is you can make more modules than you own motors

Parts You Need

• 4548 Transformer and Speed Regulator: constant, adjustable power (batteries run down uncontrollably) http://www.peeron.com/inv/sets/4548-1
• Converter Wire: 8886 (6”) or 8871 (20”)
• ~20+ Balls. Basketballs bb84pb02, soccer balls x45pb03, Friends soccer balls x45pb06, or other 1cm balls

Start With an Idea

• Explicit Directions� http://greatballcontraption.com/

http://kevinmitcham.com/gbc/

http://www.eurobricks.com/forum/index.php?/forums/topic/117305-gbc-the-akiyuki-project/

• Youtube - replicate someone else's mechanism
• Interesting parts-slides, scoops, etc.
• The world around you: escalators, oil pumps, construction sites..

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Build, Observe, Correct, Repeat...

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Troubleshooting

• Test under power as early as possible: fail early
• Being able to hand crank is also useful
• Clutch power is weak vs repeated shaking or in tension; use pins
• Connect sections with bricks or beams; flex makes things inconsistent
• Design the module for easy clearing of jams
• Any sort of funnel should have an agitator; in general agitators are good
• Build a testing jig or design the module to be able to run in a closed loop

Testing Jig

• Just a ramp to feed back from output to the hopper
• Allows close inspection of running problems
• https://dl.dropboxusercontent.com/u/8471252/GBC-Testing-Jig-with-parts.pdf
• There is no substitute for testing; things that run for 5 minutes may not run for 10

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Module

Balls roll back in the jig

Useful Links

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• Gear Placement: 'almost' gear connections are frustrating�http://gears.sariel.pl/
• Bricklink: 'I just need 4 more of these'�http://www.bricklink.com/
• Lego Technic Idea Book�http://www.amazon.com/The-LEGO-Technic-Idea-Book/dp/1593272774
• http://www.planet-gbc.com/
• https://www.youtube.com/user/akiyuky
• http://kevinmitcham.com/gbc

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Push-Arm GBC

Mechanically Simple, Common Pieces

Push-Arm Mechanism

Main Structure: A Trough

•10 studs wide x 10 bricks high x 32 studs long

•13 brick high sides for the last 8 studs (where balls leave; one end is taller than the other)

• Place pairs of 1x2 technic bricks in the walls: One at the start, 3 bricks up. One at the end, 10 brick up. These are anchor points for the ramp. One 20 studs from the front, 10 bricks up (to hold the return guide)

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Location of 1x2 technic bricks

Input End View

Side View

Up Ramp

•6 bricks high (used on its side)

•1 stud wide

•36 studs long

•Starting 11 studs in, begin the “Flex Section”. Continue “Flex” for ~8 studs

Flex Section

•Alternate 1x2 brick with 1x1 round brick

•Offset each row by 1 stud

•Round studs repeat every 3rd stud

•This is built into the ramp, allowing a bend

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Attaching the Ramp

Use technic 'half pins' and 1x1 round plates to attach the ramp to the trough.

Half pin inside technic brick with 1x1 round plate on top

1x1 round plate with stud inside technic brick

Arm Guides

Connect 2 9-hole technic beams to the remaining 1x2 technic bricks using 'slippy' pins (tan or gray).

Connection points

Drive Train Parts List

• 2x 40-tooth gears
• 2x 8-tooth gears
• 1x 3-long blue pin
• 1x 24-tooth slip gear
• 2x slip-axle pins
• 2x 3-long axles
• 1x 8-long technic brick

Drive Train Parts

Pusher Arm

• 1x 13-hole studless beam
• 1x 9-hole studless beam
• 1x 3-hole studless beam
• 1x slip-pin
• 2x 3-long pins
• 1x 6-long axle
• 4x wheels or 2x2 round

Attach the arm to the drive train’s 40-tooth gear

Assemble It

1. Place the ramp in the trough, “short” side towards the input
2. Mount the technic brick 8 studs from the input side, 13 bricks high. Two bricks added to the trough wall, then the 1x8 technic brick)
3. Tweak as needed. Too much swing may require a damper. Faster motors swing more. Solid sides help prevent the arm from snagging on the return. Larger trough needs longer arms. Different wheels on the end may require a stronger motor or changed gearing.

2 bricks up

8 studs from edge

damper

Build, Observe, Correct, Repeat