Hey everyone, Jason here. Today I am excited to
show you Kristal's latest model which is
this kinetic sculpture of a fruit bat
also known as a flying fox. So there are
four main components to the movement in
this model. The first is in the stand
which moves the entire model up and down,
and the rest have to do with approximating the
unique movement of a bat's wings, which
includes flapping them up and down, sweeping
them forward on the down stroke and also
expanding and contracting them.
Let's start with the stand. The entire motor and
drive system is mounted on this floating
frame. The motor drives this gray bevel
gear which drives two cranks on either
side of the frame through this tan gear,
and this is what gives us the up, down,
forwards, backwards rocking motion.
That gray gear also drives this small white
gear, which transfers power up
through the stand to this gear at the top, which
drives all of the movement of the wings in
the bat. To explain how the wings work we're
going to walk through all the components
of the motion as I add them to this demo
model. We'll start with the simplest
component which is flapping of the wings
up and down and for that, the wing is just
anchored to this axle here so that it
can rotate around it. And we have a crank
below that is connected to the wings
using a liftarm, so that when you rotate
the crank, the liftarm acts as a piston to move
the wings up and down. In order to
sweep the wings forward we're going to introduce
some motion into this axle anchoring the
wings so instead of having it rigidly
connected to the frame, we're going to
connect it to this pivot so that it can
swing back and forth. Now you'll notice that
the liftarm that we're using to drive the
flapping of the wings is now binding
because it's no longer operating in this
single plane. So we're going to replace
it with this link which has ball joint
sockets on each end so that it can
accommodate the new range of motion that
we're introducing.
To drive the side-to-side motion we're
going to add another crank, but instead
of attaching another piston to this
axle at a fixed point, we're going to put this
collar on it which can slide along the
axle, and we're going to attach that collar
directly to the crank, so that I rotate
the crank, the collar can slide up and
down the axle while also moving it from
side to side. The last part of the wing motion we want
to create is the expansion and
contraction of the wings, and for this
we are going to drive a simple scissor
mechanism in the wings themselves. Here's a prototype
version of the wing to show you how that
works.
So we need to move the two anchor points
of the wing closer together to expand
the wing and bring them further apart to
contract the wing. Conveniently, that collar we just
added, which slides up and down this axle
that can be used to do exactly that.
We're going to add this bar in the gap
between these two connectors on the
collar so that has the collar slides up
and down, that bar will as well. Then
we're going to attach the front anchor
of the wing here, and the rear anchor of
the wing to that bar we just added. Now
when we rotate the rear crank the wings expa nded
as they sweep forward, and contract as they come back.
A ll that's left to do is to add some
gears so that the rear cranks
rotate simultaneously with the cranks
that the flap the wings, and in this model I have
done that. There is a central axle
running down the middle with gears coming
off the sides to drive the cranks.
And that central drive axle is what is
driven by this gear at the top of the stand.
Put it all together and this is what you get.
I also wanted to note that Kristal did a
wonderful job decorating the stand.
Since these bats only come out in the evening
there's a nice sunset on one side which
transitions into twilight on the other,
with the moon and some stars.
And that is pretty much all there is to it. As always,
thanks for watching, keep on building and
I'll see you next time.
