PROJECTS: Musical Doorball Drumbot
BUILDING THE ZENBOT
After coming up with a plan, I broke the
project down into several parts. All seemingly
complicated projects are just a combination of
many much simpler components. In the case of
the ZenBot, this is what they ended up being:
1. ROTATION MECHANISM
With 14 notes on the tongue drum, I decided to
build 7 identical robots, each able to hit a note on
the larger tongue and then pivot to the smaller
tongue to hit the same note an octave higher.
Dynamixels are great for their modularity.
Designing a rotation move was as simple as
creating a bracket, Part A, that could be bolted
onto the servo horn of the base servo and also
onto the body of the second servo (Figure
A
). On
a design with stronger forces acting on the joint,
this approach would’ve been inadequate, but in
this scenario, the simple approach was sufficient.
2. STRIKE MECHANISM
Designing the strike mechanism was a little more
A B
C
Part A:
mallet rotator
Part B:
clevis
involved. It required deciding what paths I wanted
the mallet to travel within. After determining this,
I was able to pick the axis of rotation for the pivot,
as well as the second axis that the stick would
rotate around as it swung up and down. Once I
had the pivot positions figured out, I designed a
lightweight structure that supported the clevis
joint, Part B, as well as the mallet holder, Part C
(Figure
B
).
3. ANTIDAMPENING MECHANISM
I was afraid that if the servo couldn’t change
directions fast enough after hitting the drum, it
would result in a muted and not very pleasant-
sounding tone. The mallet needed to strike
the drum hard but also retract fast enough to
allow the tongue to resonate. I solved this in the
simplest way that popped into my head: Part
D. The mallet would be pushed by a stretched
rubber band. The band would stretch a bit on the
way down, then release the force onto the mallet
like a slingshot. The servo would already be
retracting as the mallet hit, then the rubber band
Part D:
anti-dampening
mechanism
Elastic band
Servo horn
Part C:
mallet holder
66 makezine.com
M81_064-69_DoorbellBot_F1.indd 66M81_064-69_DoorbellBot_F1.indd 66 4/12/22 11:37 AM4/12/22 11:37 AM
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.