Build a ping pong ball launcher

This project shows you how to build and test an adjustable ping pong ball launcher.

---

Closed Caption:


OK, so today we're
going to show you
how to make a
projectile launcher.
This launcher was
originally designed
by Dave Berggren's class in
High Tech High in San Diego.
He's an engineering teacher
there and was a mentor of mine
when I worked there.
So there are a number of
different parts on this.
We're going to talk
about each of them.
It's made out of
three pieces of wood.
There's two 1-foot square pieces
that are 3/4 of an inch thick.
Those are 3/4-inch
oak veneer plywood.
We also have another piece
here that's a 5-inch oak veneer
plywood piece, also
3/4 inch thick.
And so let's talk
about this first.
This piece has a bunch
of different holes.
They're set at 10-degree
increments along this arc,
and there's a 5/16 bolt
that you can pull in and out
and slide to change the
angle of the launcher here.
There's another
piece right here.
This is a piece of PVC.
It's 2-inch PVC.
It's screwed on to this
extruded aluminum piece.
This is 3/4-inch
extruded aluminum,
and it's connected with a
8/32 by 1 and 1/2 inch machine
screw.
And then if you
look over here, we
have a stop that's a 5/16 bolt.
And that causes the bar to stop
so that the ping-pong ball is
released.
And we have a pivot point.
That's also a 5/16 bolt, and
those are 2-inch long bolts.
And the piece of aluminum
here, this is extruded 3/4-inch
square tubular aluminum,
and it's 11 inches long.
And then we have
an eye screw here.
That's a 5/32 eye screw
that connects our spring.
This spring is a
15/32 3-inch spring.
And then we have another
5/16 bolt, a nut,
and we've countersunk a hole so
the nut sits below the surface.
Let's take a look
on the inside here.
We've also created some holes,
so we have a 5/8-inch center
hole and a 1-inch hole.
And the 1-inch hole goes
down about 1/8 of an inch.
The 5/8-inch hole goes
down about 1/2 an inch,
and that allows the nuts
and washers on the backside
of these bolts to sit inside
the bottom piece and for the two
pieces of wood to sit flush,
which allows for 0 degree angle
launches and things.
We also have 2 and 1/2 inch
hinges here in the back,
and so that's pretty
much the launcher there.
Let's go ahead and get started.
So this is our launcher, and
it's the original design.
We've got the angle
adjustment mechanism here.
You pull it back, and
you can launch it.
So that's basically
how it works.
You can pull the pin out, drop
it down, and have it flat.
So you're going to
need a saw to cut
the wood-- a circular
saw will work great,
like this one-- a drill
to put some holes in it.
You're going to
also need a square.
A try square like this works.
You can also use
a rafter square.
And something to determine
angles-- a compass.
A file is important.
You're also going to need a
wrench and a pliers, hacksaw,
and some spade bits
and spiral drill bits.
So we've got our 3/4-inch piece
of oak veneer plywood here,
and we've got all
our parts laid out--
so our PVC and our different
assorted washers and nuts.
And you can see that we also
have our different bolts
and springs there, as well, and
our piece of extruded aluminum.
And so we're going
to go ahead and start
making our first
hole, and that's
going to be the hole
for the 5/16 bolt that
holds the spring in place--
that bolt right there.
And so the way we
do this is we have
two nuts on either
side of the bolt
that we tighten down
against each other
to hold the bolt in place
and keep it nice and stable.
We're going to use a
7/8-inch spade bit.
And we've got it taped about
a 1/4 inch up, so we only
go down 1/4 of an inch.
And that'll allow us
to countersink a hole.
And then we're using
our 5/16 spiral bit
so we can put our
bolt in the wood.
And we're getting
everything set up.
This is our pattern we
drew on the computer,
and we're going to
use that pattern
to cut out different angles.
We're going to use a small 3/32
bit to drill pilot holes, which
makes it easier to
drill our larger
holes with the 5/16 bit,
which is the size of the bolt
that we'll actually have there.
So the pilot holes help us
to guide that larger bit
into the correct location.

OK, so now we're going
to drill the center hole.
And we're going to
use a 7/8 drill bit.
It's a spade bit.
We've got it taped
1/4 of an inch up,
and that will allow a
recess for both our top nut
and our washer to sit in.
And then we'll use
our 5/16 spiral bit
to finish off the hole.
Now we're going to drill
our countersunk holes.
These are the holes that
go in the bottom piece
and allow the washer and nut
and bolt protruding from the top
through the bottom of the top to
sit inside of the bottom board.
So we're just marking
the center points
for all of those
different bolts,
and we're going to use
a 1-inch spade bit.
And we'll go down about 1/8
of an inch with that 1/8 inch
spade bit.
We're taping that off
about 1/8 of an inch,
and then we're using
a 5/8 inch spade bit
to go down the rest of the way,
which is about 1/2 an inch.
And that'll leave enough
space for the washer
and the end of the bolt.
So there's the 5/8 inch spade
bit going the rest of the way.
And make sure you do the
smaller spade bit second.
Now we're going to go ahead
and set in our hinges.
They're measured about
an inch in from the edge.
They're about 2 and
1/2-inch long hinges.
So we've lined everything
up with the aluminum,
clamped it down,
lining the hinges up,
and then we're just
marking the centers.
And now we're going to take a
1/16-inch drill bit and tape it
about 1/2 inch up.
And so we've got
the holes, and we're
going to put our
screws in, not going
in all the way just yet,
but most of the way.
And then we're going
to mark the other side
and put the holes in for that.
And now we're going to put
our screws in on that side.
And then we'll go through,
and we'll tighten all of them
down the rest of the way.

All right.
So now we're going to cut the
angle portion, the part that
has the arc of
holes that allows us
to set the different
degrees of angle.
So we are just using
our aluminum as a fence.
We're marking our part there.
This is the last cut
we have to make on it.
It's 5 inches square.
So we'll take our circular
saw and trim that off.
All right, now
we've got our piece,
so we're just going
to file that off
very quickly to
clean up the edges.
And now we're going to tape a
pattern that we printed from
the computer and use our
3/32-inch bit to create
our pilot holes.
So we'll put our
pilot holes in that.
And now we'll use our 5/16-inch
bit to finish off the holes,
make them the full size.

All right, so that's the
part that we just made.
We're getting it
lined up and centered.
And we're going to mark it to
line it up with our device,
and we're marking it so that we
can put our screws in about 3/8
of an inch up from the
very bottom of the device.
That means that
the screws will be
in the center of the bottom
board we're screwing into.
And we're using
1/16-inch drill bit,
and we're spacing those holes
about 1 inch and 1/4 apart.
I'm going to use some 1 inch
and 1/2 long panhead wood screws
to hold the angle
piece in place.
So we're just
drilling those holes
and putting those
wood screws in right
now, tightening it all down.
And we'll check to make
sure that it all fits
right and moves, and it does.
OK.
So now we're going to
cut our launcher bar.
And we're just using a hacksaw.
That's measured at 11 inches,
so it sits inside the edge
from either side
about 1/2 an inch.
And we're cleaning it
up with a file there.
And now we're going to mark our
center and drill our center.
We're, again, going to use the
3/32-inch bit to create that
pilot hole.

And then we'll
take the bar down,
and we're going to line
it up with the pieces
that we want to
bolt onto the bar.
And so we've got our PVC
there and our eye screw
for the spring.
So we're going to drill the
holes for those two components.

All right, so we're
drilling our pilot holes
in the aluminum bar that's going
to launch the ping-pong ball,
and that's a 3/32 bit there.
Now that we have
our pilot holes,
we can put the larger holes
in place for our eye screw
and for the machine
screw that's going
to hold the PVC cradle in place.
Now we're making our PVC cradle.
And we're just going
to cut it in half,
using a clamp and a hacksaw.
And in order to
get it just right,
we need to reposition it there.
Now, the hacksaw
leaves a rough edge,
so we'll clean edge up with
a break-off blade knife.
You want to be
careful doing that,
so you don't cut yourself.
And then we'll use a
file to just smooth off
the edges the rest of the way.
Then we'll mark the center
about 3/8 of an inch up
and drill a pilot hole
and then our final hole.
Now we're going to assemble
all the different components.
We're inserting washers and then
nuts on the top, lock washers
and nuts on the bottom for the
bolt holding the spring in.
And now we're going to
put our eye screw in,
and then we're going to
insert the center pivot screw.
And that's got two
nylon washers and then
two washers and two nuts
and a lock washer on it.
So we can tighten that down.
That holds the bolt in place
but still allows the aluminum
to spin freely,
you can see there.
Now we're going to
put our stop in place,
and that's just
another 5/16 bolt
with some nylon
washers around it.
And we've got a PVC cradle
that we've trimmed out there
for our machine screw, because
it's got a flanged head.
And we're tightening
that down now.
So we'll use our wrench to hold
that in place and a screwdriver
to tighten that up.
So we've got our
cradle ready to go.
So now we're going
to take the spring
and try and attach it using our
needle-nose pliers to the eye
screw, and then we're
going to take our launcher
and take it outside
and do some tests.
We did a number
of tests with it,
and we found that some
of the time, the ball
would curve to the left.
And so we're going to make
some design modifications
in our next video.