Hey everyone, Jason here. Today we are
going to take a look at Kristal's latest
model, which is the small sculpture of
the World Turtle, also referred to as the
Cosmic Turtle. If you are unfamiliar with
the concept of the World Turtle,
it's an idea shared among several
mythologies about how the earth travels
through the universe, being supported by
four elephants on the back a giant
turtle. Terry Pratchett also used this concept as
the backdrop for his Discworld series of
novels, so if you are a fan of fantasy
novels you may be more familiar with it
from that source. One thing you might
notice about this model is there is no
crank on it, which makes it a nice clean
display piece, and that is because the
world itself acts as a crank. By spinning
the world you can make the turtle appear
to swim. So, let's take a closer look at
how it works the earth sits on top of
the model and it has these mountains,
a little forest here, a river to the
waterfall off the edge, and this little
settlement. Definitive proof that the
world is indeed flat, right here folks.
The earth is mounted on these 2 by 2
round bricks with an axle hole through
them, and they just sit on this axle here
at the centre of the elephants to drive
the swimming mechanism. So, we'll take off these cute elephants and the back of the
turtle to see what is going on inside.
It's actually all quite simple, which it
kind of needs to be to fit in this small
space. There is a black gear at the
bottom of the drive axle which drives
this tan gear, and that tan gear is
connected to a small crank and piston,
which drives the head of the turtle back
and forth. The inside of each fin is
connected to the head assembly so that
they also move back and forth with the
head, and the center of each fin is
mounted to the base of the model so that
they act as simple levers. As the inside
of the fin moves forward, the outside of
each fin moves backwards and vice-versa.
As a result, you get this nice little
coordinated motion between
head and the fins, which gives the
impression of the turtle swimming.
As I was preparing to make this video I was wondering how I would do the
introduction. Since there is no
externally exposed axle to drive the
mechanism, there's no easy way to connect
an external motor to power the turtle.
But, I did notice that there was just
enough room in the back of the turtle to
fit one of these old 9-volt micro motors.
Now one nice thing about these micro
motors is that they don't spin very fast
which means you don't need to gear them
down at all to drive a kinetic sculpture
like this. Of course there are some
challenges with using these motors. Aside
from the fact that Lego hasn't actually
produced them in the last 20 years,
there's no way to easily attach a gear
to it. There's no axle or axle hole in
the motor, it's just a LEGO stud that
rotates on the drive shaft. So, I had to get
a little bit creative, but I discovered I
could use this relatively new part, this
1 by 1 round tile with a bar sticking
out of it, and there's actually enough
friction between that bar and a gear
mounted on it to actually drive the gear.
Now, I actually ended up using the
transparent version of that part because
it offers just a little bit more
friction, and then we can just stick that
part on to the stud of the motor, and
we'll apply some power to it, and there
we go.
I did have to modify the back of the
turtle a little bit to accommodate the 9 volt
connector and the wire coming out
of the motor, but otherwise the motor
nestles in there quite nicely.
If you'd like to build your own copy of
this model there are building
instructions available, you can head on
over to jkbrickworks.com to find those.
And, that is about all there is to it.
Like and subscribe if you like this
model and would like to see more. As always, thanks for watching, keep on building,
and I'll see you next time
