Blue Fox - K'nex Ball Machine





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Published on Jul 14, 2011

This is Blue Fox, my most complex K'nex structure to date. This ball machine has 17 paths, 22,000 pieces, 6 lift mechanisms (including a computerized robot arm) and 7 motors. I designed and constructed this machine over the course of over 10 months, due to a lack of free time during the school year. The ball machine is supported on a system of three giant arches, which are actually sections of the curved support for my world-record-setting K'nex looping roller coaster. This video was directed and filmed by Kevin C. Walker (http://www.KevinCWalker.com).

Some one-of-a-kind elements in Blue Fox include:

- Computerized robot arm ball lift
- Bi-directional ferris wheell path switcher (gives the machine "moods")
- Automatic repeating ball launcher
- Anti-gravity track (ball accelerates while moving uphill)
- Giant Tube (Big-Air Ball tower clear tubing used as an overhead bridge)
- Illuminated Loop (Arduino-controlled LEDs chase the ball around the giant loop)
- Glowing LED Ball

Build time - 10 months
Pieces - 22,000
Motors - 7
Ball Lifts - 6
Paths - 17
Switches - 12
Moving Parts - 120
Gears - 86
Max Balls - 20


Q. What is the song?
A. The song is Last Days by Max Richter.

Q. What did you use to illuminate the machine?
A. There are 3 strings of 25 foot blue rope light and 3 blue outdoor flood lights. In addition, there are 24 ultrabright LEDs scattered throughout the machine.

Q. What camera did you use?
A. The majority of the video was filmed with a Canon EOS 7D. The wide-angle and time-lapse shots were filmed with a Samsung TL350 (what I use for most of my videos), and the high speed shots were filmed with a Casio Exilim EX-FC100 at 210 frames per second.

Q. How did you construct the LED ball?
A. The LED ball has 2 ultrabright blue LEDs connected by a small switch to 3 LR44 button cell batteries which supply 4.5v. See my blog (http://knexdesigns.blogspot.com) for details and pictures.

Q. How do you sleep at night?
A. I turn the machine off!

Q. How do you turn it off and on?
A. I have every motor and light wired to a single power strip. Everything is turned on with the push of a single button.

Q. How does the Ferris Wheel give the machine "moods"?
A. The Ferris Wheel has quite a lot of momentum, so it keeps spinning after a ball has gone through it. The direction it is spinning determines which of the two towers on either side of the wheel the balls are fed into. because these towers lead to different ends of the machine, the direction of the wheel directly effects the amount of activity in different areas of the machine. It switches direction on average once every minute and a half or so. Its purpose is to add an element of chaos and unpredictability to the machine, going beyond simple rocker switches.

Q. What motors did you use?
A. I used 5 standard K'nex 9V plug-in motors, and one 12V geared motor I bought from a surplus store.

Q. How did you build the robot arm?
A. The robot arm is controlled by an Arduino microcontroller which is programmed using the C programming language. two bi-directional motor control circuits using DPDT relays controls two K'nex 9v plug-in motors.

Q. How often do balls fly off the track?
A. I spent nearly 3 weeks meticulously testing every track and moving part on the machine, and it now runs with great reliability. However, when all 20 balls are in, a ball will fall off every ten or so minutes.

Q. How can you move about in your room?
A. Surprisingly, Blue Fox takes up only 18 square inches of floor space! Everything else is elevated 6 feet or more off the ground on a series of arches and towers. Though it does not look like it, both doors in my room CAN open all the way. Blue fox is the least intrusive ball machine I have ever designed.

Q. Why "blue fox"?
A. Simple. Blue is my favorite color and Foxes are my favorite animal.

Q. No, really, why "blue fox"?
A. ...fine. I painted my room blue to get rid of the old pink/purple wallpaper which was put in by this house's previous owners. I then decided to go for a more sleek lighting scheme and installed blue rope light, rather than the chaotic Christmas lights of Labyrinth and Subatomic Paraball. I spent quite some time sketching out rough outlines for the 'centerpiece' of the machine, the part which would sit upon my dresser in the middle of my room. I began drawing plans for a symmetrical tower with a ferris wheel in the center and realized that the overall shape was beginning to look fox-like. I modified the plans to incorporate that, and used as many orange pieces as I could. I then added the eyes (yes, those are supposed to be his eyes...) and that was that.

If you have any further questions, feel free to send me a message or leave a comment. I do read every single comment I ever get, and I respond to the thoughtful ones.

To see details on Blue Fox's construction and to follow the design and construction of my new projects, visit my blog: http://knexdesigns.blogspot.com


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