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Step 2: Mechanics

A project log for Making Techno with Music Robots

I was bored with synthesizers, but still wanted to make electronic music. So I build a lot of techno music robots!

Moritz Simon GeistMoritz Simon Geist 09/22/2018 at 21:410 Comments

So I want to use my newly developed 808is -ike-futuristic-kalimba-robot as a music instrument on stage and it has to be stable. To build quick-and-dirty mockups is fine in the workshop and maybe studio - once a experimental hacked-together instrument breaks in front of a several hundert people audience and lets you leave stage in embarrassment, you swear to yourself to go the last mile the next time.

I have a lot of actuators in my workshop, motors, solenoids, stepper motors, gear motors. I don’t usually work with pneumatics, and I like DC motors from 12-24V most. I normally search on ebay or pollin (german cheap reseller) for cheap stuff and buy always 5-100 in bulk. Also I wrote Schulz Magnete (a high quality german solenoid manufacturer) and they gave me some of their over-stock for free. Very generous!

I often experiment with a lot of different solenoids to find the right one in terms of force and build volume. For this build I am using some solenoids (electromagnets) from Schulz magnet. The solenoids I bought from china often had a poor quality, in terms of mechanical precision (how the anchor moves in the coil) and of efficiency (electrical power-to-mechanical force ration).

When I started building robots I used a lot of wood, old piano pieces and old stuff I found on the scrap market. Then, I bought my first Makerbot 3D printer in 2013 and it changed my build from custom-made unique copies, to reproducible devices.

I design everything in Autodesk Inventor, and I designed most of my standard devices (solenoids, motors, LEDs, connectors) as 3D Models. I now have three 3D Printers in my workshop, two Replicator 1 and one new Prusa i3 (love it!) for more experimental material than PLA.

Since I have my 3D printers I print everything I can, and insert metal parts (e.g. as screw inserts) where I need more stability. For my last instrument TRIPODS ONE I also ordered some custom welded aluminum parts from a local welding shop.

for the building and designing process, working with 3D Printing mostly means I can use an iterative process. I sketch the rough idea by hand, maybe build a cardboard and wood model and then it takes 3-8 3D-Printed iterations until I have my last design. This definitly creates a lot plastic trash, but I give it to my local fablab in Dresden where they recycle it.

With the length of the spring steel you can change the pitch of the instrument. I ended up using five different tongues for different tones.

What I want to do to improve this is using a special made corpus that supports the frequency of the tongue. Every acoustic body has some main frequencies to it – you know that from an empty room with a standing wave, or from an empty bottle where you beat on. A normal instrument builder would avoid that: A guitar body for example tries to have more softer body-frequency spectrum with little spikes. But we can uses that to support our main frequencies of our bass drum tongue! Longer decay and a softer tone. I am currently building such a tuned body and will keep you posted about the progress.

Robotic Kalimba Prototype
Robotic Kalimba Prototype
Robotic Kalimba Prototype
Robotic Kalimba Prototype
The Final robotic Kalimba
The Final robotic Kalimba
Robotic Kalimba on Stage

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