MechBass: a robotic bass guitar that sounds fantastic

[James] wrote in to show us his honors project for his fourth year at Victoria University of Wellington. He designed and built this robotic bass guitar. You can hear it performing “mass hysteria” by the band Muse after the break. It sounds great, but we’d love to hear it without the full accompaniment.

[James] doesn’t have a site up for the MechBass, so we’ve included details below.

  • Everything I designed in Solidworks, and lasercut/3D printed and assembled my self. Most components went through 3 or more design iterations.
  • The pitch shifter is open loop, with a NEMA23 stepper driving it to the desired position, and limit switches allowing alignment upon startup. Carriage is a custom design, riding on 80/20 using their low friction bearing pads. An igus cable carrier manages the wires for the solenoids during movement.
  • The control board is a completely custom design, based upon the ATMega328 (for Arduino compatibility), and as such is programmed with that IDE. Stepper motor drivers are dropped in that interface between the Microcontroller and stepper motors, while a MOSFET drives the solenoids. MIDI interface follows the MMA standard for connecting the devices on a bus. Each string only responds to MIDI messages on their designated MIDI channel. Decoupling capacitors and TVS’s in close proximity to the drivers are present to minimize transients during braking of the stepper motors (particularly the one for the pitch shifter).
  • A servo beneath the pickwheel stepper motor enables the motor to be pivoted, bringing the picks closer to or further away from the string, allowing the volume of the picks to be altered.
  • Felt covered arm attached to a servo allows for damping (muting) of the string on demand (noteOff).
  • An optical pickup is employed instead of the traditional magnetic pickup, due to the large amount of electromagnetic noise associated with all the actuators of the system.
  • Traditional bass machine heads are used for tensioning the string, integrated into the top of the main pitch shifter assembly.
  • Power supply box at back houses 3 power supply units (5V and 2x 24V, 750 watts total), attached to modular connectors for connection to each of the boards. 5 V supplies logic and servos, as well as the pickups (through a 3.3V LDO regulator on a board close to the pickups), while one 24 V supplies the solenoids, and the other for the stepper motors.
A large amount of attention to detail was paid in this project, for example all the servo cables were manually extended, while every cable is neatly sleeved and heatshrunk, with molex connectors for all actuators. Over 800 bolts in total in the project… Among many other things.

If you want some detail shots and tons of information about the design and operation, there is a short PDF that [James] supplied, available here (whoops, he wasn’t supposed to publish that. Website coming soon)

Comments

  1. John says:

    Awesome!

  2. bufalo1973 says:

    What about an “Anesthesia (pulling teeth)” (Metallica) version? ;)

  3. Matt Lokes says:

    The song is called Hysteria not Mass Hysteria!!!! :( Awesome project though :)

  4. Jan says:

    Great project, Very impressive!
    Well done :-)

  5. bufalo1973 says:

    What about an “Anesthesia (pulling teeth)” cover? :)

  6. rhyno001 says:

    Sorry if this is kind of a n00b question…What is the name of the aluminum stock he used for the structure of his design? I’ve heard it called a few different names, but I can’t remember any of them

  7. icanhazadd says:

    This mechanical bass ought to get together with the MR-808 and robojam :)

  8. six677 says:

    Damn thats actually very nice, where can I buy one xD

  9. Caboose says:

    Commonly known as profile or extrusion (http://en.wikipedia.org/wiki/Extrusion)

  10. very nice says:

    very nice. Deserves a high mark imo!

  11. Henry says:

    Free Bird! :-p

  12. cruster says:

    Just amazing! Well done. :-)

  13. holy cow! amazing!

  14. I’m a little sad we only get to hear the clean sound from the optical pickups and not the beautiful robot choir of stepper motors in the background :)

  15. foxdieuk says:

    Look out Christopher Wolstenholme ;)

  16. wowme@wtf.com says:

    this is not a hack!
    this is well engineered genius
    Now like SSVENN said, i want to hear the hardware!

  17. wowme@wtf.com says:

    “If you want some detail shots and tons of information about the design and operation, there is a short PDF that [James] supplied, available here (whoops, he wasn’t supposed to publish that. Website coming soon)”

    Haha found it anyway!

  18. wowme@wtf.com says:

    Not trying to be prolific this evening, just this is an interesting project.
    James has two youtube postings

    http://www.youtube.com/channel/UCyXnpr0Fu1s0CADsthLimpA/videos

  19. Angelabsurdist says:

    Genius.

  20. Julez says:

    Damn that is sweet, great song choice too well done mate.

  21. Cameron says:

    That is slick!

  22. word clock says:

    yep, lets hear those steppers work!

  23. Nova says:

    He added a third video without background music. A good question is if these are taken with an external mic or off the optical pick-ups. http://www.youtube.com/watch?v=KW9nYOlT89M&feature=plcp

  24. Lewis says:

    Absolutely fantastic use of imagination! Very impressed!

  25. Matthias_H says:

    So how well does it do in the Jamiroquai benchmark?

  26. Jef says:

    Quote:
    So how well does it do in the Jamiroquai benchmark?

    Pfft Bootsy Collins…

    This is great. How long before the rest?

  27. Nice build! It occurs to me that if the acrylic ‘frets’ and ‘fingers’ were replaced with small pulleys, the carriage sliding would bend the pitch.

    • James McVay says:

      That was the next stage in the project, which I’m going to begin working on, just figuring out the most elegant solution to add the rollers in place of their current acrylic counterparts.

      • How about mounting them on opposite edges of a disc with its axis perpendicular to the string, so that, as it turns, one pulley is rotated down onto the string, while the other is rotated up. It’s a simple mechanism that, if made strong enough, could even be used as a tensioner.

  28. Camille Moussette says:

    Amazingly similar to GuitarBot from Lemur/Eric Singer. Nice build anyways :-)

    http://lemurbots.org

  29. MINK.INK says:

    How awsome this is!!!!!
    Could be interresting for some post rock styles
    but I´ve got a question how fast can it play.

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