Programmable Knex Piano-Playing Robot





Introduction: Programmable Knex Piano-Playing Robot

About: You don't have to be a kid to love k'nex!

I've always been a big fan of K'nex, ever since I was a little kid. Then, when I discovered this website, I felt like I had hit the jackpot. This is a "robot" that I built out of knex, it's designed to play the piano. This version can play up to a 16 note sequence in a 12 note range. I call it "Zeeanobot" (Zach's Piano Robot), corny, I know, but I couldn't think of a better name. I spent a lot of time on this, and I'm very proud of it, so please be nice. Just to be clear, I have not tried it on a real piano, I built it to play my Yamaha DGX-230. You may need to modify the design slightly to get it to work on real pianos or other keyboards.

Please note that this is my first real instructable, so I'd appreciate any constructive criticism. Thanks. (So far the response has been mostly positive, so thanks everybody! I put a lot of work into designing and building this so I'm very proud of it. I'm glad you like it too.)

The first video is a mechanical view of Zeeanobot, showing how it works.

The second video is Zeeanobot playing a simple proof of concept song.

The third video is a duet of Katy Perry's "Hot and Cold". Ignore the errors on my part, they're not the point.

The final video is a duet of "Heart and Soul".

Step 1: Materials

Materials Required:


6 x Black Rods
25 x White Rods
100 x Blue Rods
104 x Yellow Rods
23 x Gray Rods


20 x Gray 1-Prongs
60 x Gray 2-Prongs
4 x Brown 2-Prongs
41 x Red 3-Prongs
28 x Interlocking Gray 4-Prongs
1 x Green 4-Prongs
54 x Yellow 5-Prongs
20 x Interlocking Blue 7-Prongs
18 x White 8-Prongs


63 x Blue Spacers
48 x Gray Spacers
2 x Small Blue Gears
8 x Medium Red Gears
2 x Big Black Gears
48 x Chain Links
37 x Tan Clips
1 x Motor
1 x Piano (Optional)

Step 2: Build Right and Left Base Modules

Build two of these, a right one and a left one. They're exactly the same except for the two yellow rods on the right side of the left module. See the picture for more details.

NOTE: I didn't have enough yellow rods, so I used the gray rods that are the same length as the yellow ones. I needed to make several substitutions, so the colors may vary.

Step 3: Build Fingers

You need to build 12 of these. The double construction, is essential. It gives the fingers the necessary strength and stability they need to function properly.

Step 4: Build Hands

You need to build two of these. Then pivot the movable pieces so the Gray 2-Prong clips are resting in between two yellow rods.

Interlocking Gray Connectors --- Gray Spacer --- Blue Spacer --- Gray Spacer --- Blue Spacer --- Gray Spacer +++ Yellow 5-Prong Clipped On --- Yellow 5-Prong Threaded Through The Hole --- Blue Spacer --- Yellow 5-Prong Threaded Through The Hole --- Repeat From +++ 5 More Times --- Yellow 5-Prong Clipped On --- Interlocking Gray Connector

Step 5: Build Programmable Armatures

Build two of these. To program the robot, you will insert pegs into the White 8-Prong connectors, but don't worry about that now, I'll explain more later.

Gray 1-Prong --- Tan Clip (n-) --- Medium Red Gear --- Medium Red Gear --- Tan Clip (-n) +++ Yellow 5-Prong --- Blue Spacer --- White 8-Prong --- Tan Clip (-n) --- Repeat from +++ 5 More Times --- Yellow 5-Prong --- Gray 1-Prong

NOTE: (n-) and (-n) indicate the direction of the peg on the tan clips.

Step 6: Build Rear Supports

Build two of these.

Gray 1-Prong --- Blue Spacer --- Gray Spacer --- Blue Spacer --- Gray 1-Prong (Threaded Through The Hole) +++ Blue Spacer --- Gray Spacer --- Blue Spacer --- Red 3-Prong --- Repeat From +++ 6 More Times --- Gray 1-Prong

Step 7: Attach "Fingers" to "Hands"

Attach six Fingers to each Hand. The Yellow Rods on the Fingers go into the top slot of the Yellow 5-Prong connectors on the Hands. The Blue Rods on the Fingers go into the 45 degree slots on the Hand's Yellow 5-Prong connectors.

Step 8: Attach Hands to Base Modules

Pretty self explanatory. Just note that the end of the Hand that has all the spacers on it, is closest to the camera. Also note that the Gray Rods may bend slightly, that's how it should be.

Step 9: Attach Programmable Armatures to Base Modules

Slide the Programmable Armature onto the Gray Rods of the Base Module. Then attach the "Hand's" Yellow Rods to the Yellow 5-Prongs on the Programmable Armatures.

Step 10: Attach Rear Supports to Programmable Armatures

Now slide the Rear Supports onto the Gray Rods of the Base Module. Then attach the Rear Support's White Rods to the Yellow 5-Prongs on the Programmable Armatures. You should now have two complete Base Modules. If not, repeat the earlier steps to complete the second module. They should look like the 4th picture on this page. They should be nearly identical at this point.

Now hook the two Base Modules together using the two Yellow Rods on the Left Base Module.

Step 11: Construct Left Drive Train

You need just one of these.

Tan Clip --- Red 3-Prong --- Gray Spacer --- Gray Spacer --- Tan Clip (n-) --- Red Gear --- Red Gear --- Tan Clip (-n) --- Gray Spacer --- Gray Spacer --- Blue Spacer --- Blue Spacer --- Gray Spacer --- Gray Spacer --- White 8-Prong --- Gray Spacer --- Tan Clip (n-) --- Black Gear --- Tan Clip (-n) --- Gray Spacer --- Gray Spacer --- White 8-Prong --- Tan Clip (Snapped On, Peg Facing Out)

NOTE: I had to use Gray Gears in place of the Red Gears because I didn't have enough, but they're the same size and have the same number of teeth, so they're interchangeable.

Step 12: Construct Right Drive Train

You need one of these.

You can clearly see how the front Gray Rod is arranged so the configuration below is for the Gray Rod with the Black Gear on it.

Tan Clip (Clipped On, Peg Facing In) --- Gray Spacer --- Blue Spacer --- Red 3-Prong --- Gray  Spacer --- Gray Spacer --- Tan Clip (n-) --- Red Gear --- Red Gear --- Tan Clip (-n) --- Gray Spacer --- Blue Spacer --- White 8-Prong --- Gray Spacer --- Gray Spacer --- Tan Clip (n-) --- Black Gear --- Tan Clip (-n) --- Gray Spacer --- White 8-Prong --- Gray Spacer --- Blue Spacer --- Tan Clip (Clipped On, Peg Facing in)

Step 13: Construct Center Drive Train

You need one of these.

NOTE: Depending on which motor you are using, you may need to make some slight modifications. The motor I used is big and gray, but I don't remember what set it came with.

You can clearly see how it is arranged in the picture, however, there is one correction that I've made since I took this picture. See the notes on the picture for more details.

Step 14: Connect the Left, Center, and Right Drive Train

Okay, I know this is hard to see, well its also pretty hard to describe, but I'll do my best. The second picture makes it clear how to attach the Center Module to the Right Module.

Step 15: Attach the Drive Train to the Base Modules

If you've done everything correctly up to this point, it should be very clear how the Drive Train attaches to the Base Modules. Now, add two Chains, 24 links each to connect the Gears on the Drive Trains to the Gears on the Programmable Armature. You should now have a near complete "Zeeanobot".

Step 16: Construct and Attach Support Structure

This part will probably require some customization but I'll post the one I built for my Yamaha DGX-230.

Step 17: Programming and Fine Tuning

Programming Zeeanobot is simple. You just put White Rods in the White 8-Prong connectors. This way, when you turn on the motor, it spins the drive shaft, which is attached to the Programming Armature via a chain. The White Rod that you put in the Armature then pushes up the finger, which pivots around an axle on the Hand, thus causing the front of the finger to push down on one of the piano keys. The White Rod will then pass in between the top part of the fingers releasing the key. If you find that the White Rod doesn't make it through the two Yellow Rods, move the Gray Clip on the Hand away from the Programming Armature.

You may have some synchronization trouble at first (between the left and right modules). You can fix this by taking off the Chains and lining up the holes of the White 8-Prongs on the left and right modules.

Step 18: Play Beautiful Duets

If you've made it this far, congratulations. Hopefully it hasn't taken you as long to build as it took for me to design. I happily accept any constructive criticism or improvements on my design or my instructable. I plan to refine this 'ible' over time, clearing up some of the confusing parts, but for now it will have to do. I'll be happy to answer any questions you may have, so just leave a comment.

All that's left for you to do now, is to start learning some great duets.



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    85 Discussions

    You should enter this in the first time authors contest. I'd think you'd win grand prize. ☺

    This is interesting!!!!

    I'm probably the first comment you've had in a while.........................................can you use the smaller chain links? I'm all out of regular.

     Guess what my two favourite hobbies are? Teh same ones as yours!  I have a mamod sp4 and  the mamod car (in green), my sp4's piston exploded in my brother's face it was the funniest reaction I have ever seen in my life!

    6 replies

     Well it popped off, but the crank rod snapped in half because it was still attached to the crank

    nice! BTW, be on the looks out for the knex lemonade machine MKIII, preliminary tests are all good!

    I am acualy building a steam engine myself. it teams to have alot of power for a boiler that size. What is the size of the cylinder?

    It is very good u should be proud, may i ask how long did it take to make