Download Report

How to
make a
Tabletop
trebuchet
Developed by Brian Bowes
Meason Kolkhorst, Carl Schwab
and Randy Scrudder
June 2008
Supplies
You Will Need The Following:
Safety Glasses
Approximately 70 Craft Sticks
Glue Gun (Low Melt)
2 - 3 Hot Glue Sticks
Approximately 7 feet of String/Twine
Approximately 4” X 6” Piece of Cloth
Paperclip
1/4” Wooden Dowel
(4) 1” Wooden Wheels
Large Empty Medicine Bottle
Plastic Golfball or other Projectile
Empty Soda Cans (Castle Wall)
Before You Begin
Always wear safety glasses while you are working
on your project.
Hot glue burns! Keeps your fingers away from the
melted glue and the tip of the gun.
Making the Base
Step 1
Begin by gluing three
sticks together like
this.
Step 2
Now, turn it over,
add another stick to
the top.
Step 3
Add two more
sticks on top of
what you did in
Step 2. Your sticks
should be glued
together like this.
The end structure
will be 6 sticks glued
together alternating
1 stick, 2 sticks, 1
stick, 2 sticks.
Step 4
Repeat Steps 1 thru 3
and make another one so
you have two of them.
You have now manufactured the left and right
sides of the base.
Step 5
With both sides facing
the same direction,
glue a stick between
the two as shown.
Make sure that you
glue the stick INBETWEEN on each
side.
Step 6
Turn the base around
and glue another stick
on the other side.
Step 7
Add two more sticks
to each end on the
bottom of the base.
It should look like
this.
Put this piece aside
for now. You will
need in later.
Making the Sides
Step 8
Now you are going to
make the sides of the
trebuchet.
Using 3 sticks, stack
and glue them together
similar to what you did
in Step 1.
Make four pieces that
look like this.
Step 9
Using two of the pieces
facing opposite of each
other, criss cross two of
the side pieces.
Do not glue these together
until Step 10.
Step 10
Glue one stick to
each side of the
long end of the “V”
that you have created.
DO NOT glue the
top of the “V” until
you get to Step 22
Step 11
Repeat Steps 8 thru
10 so that you have
made two side
pieces.
Put these pieces
aside for now, you
will need them later.
Throwing Arm
Step 12
It is now time to make the
throwing arm. Start by
gluing 5 sticks together as
shown.
Step 13
Repeat Step 12 so that
you have two identical 5
stick long pieces.
Please note that the long
side has 3 sticks and the
short side has 2 sticks.
Step 14
Glue the two pieces from
Step 13 together. Be sure
that they are facing the
same direction. The ends
of the two pieces should
be even with each other.
Please note again, that the
long side has 3 sticks and
the short side has 2 sticks.
Step 15
Glue on two more
sticks on the long
side of the throwing are. It should
look like this.
Step 16
Finish the throwing
arm by adding two
additional pieces to
each side of the
throwing arm.
This will add strength
to the arm.
Step 17
You must now determine where the axle for the throwing arm
should be attached. There is a ratio for determining where that
point is. That ratio is 4:1.
Where a Fraction is the proportion of a part of
something compared to its whole, a Ratio is the
proportion of a whole compared to its parts.
They are always expressed as whole numbers,
never as fractions.
Non-Example: 5:1/2
Example: 10:1
A ratio of 4:1
means that you
have a measurement of 4 units on
one side, and 1
unit on the other
side
When you add
this together, you
will have a total of
5 units.
: 1
4
5
Now you need to measure the length of your throwing arm in inches. Once you
have that length, divide it by 5. This will allow you to determine the measurement
for one unit.
Measure that length from one end of the throwing arm, and mark it with a pencil. This is where you will attach the axle for the throwing arm.
Step 18
Retrieve a dowel and measure and cut a 6 inch piece from
one end. This will be the axle for your throwing arm.
Step 19
Place a drop of glue on
your throwing arm at
the spot you measured
in Step 17. Center and
attach the 6 inch dowel
to the throwing arm.
Step 20
You now need to cut a
piece of string that is
approximately 3 feet
or 36 inched long.
Step 21
Lash the axle to the throwing
arm with the 3 feet of string.
Wrap the string tightly and
use a little hot glue to help
hold it in place.
The picture below is from the
Boy Scout Handbook, and it
describes how to lash the two
pieces together tightly.
Attaching Sides
Step 22
Retrieve your base and
(2) sides. Center the
sides inside the base
and glue them in place.
Be Sure You
*Align
*
the sides so that
the tops of the “V”s
are parallel to each
other, and so that the
sides are perpendicular
to the base. Glue the tops of the “V” in place so that they do not move around.
Step 23
Once the sides are
in place, glue on
support sticks.
Make sure that
they are attached
to the base and the
sides.
Step 24
Next, glue an upright support piece
on both sides. The
stick fits in-between
the two sticks which
are at the bottom of
the side structures.
Step 25
Now, glue a cross
member support
piece as shown. Do
this for both sides.
This cross member
can also help to
make the sides more
perpendicular by
placing the stick on
the inside or the
outside of the
trebuchet.
Step 26
Create a platform
for the projectile to
rest on while it is
being hurled. Use 5
or 6 sticks and glue
them to the support
sticks you attached
in Step 23.
Wheels
Throwing Arm
Wheels help to “soak” up the energy created by the heavy counterweight. They also help the trebuchet hurl the projectile further.
Step 27
Now gather your (4)
wooden wheels and the
drinking straws. Cut the
straw so that you have
several 1 inch pieces.
Step 28
Again, retrieve a dowel and measure and cut two (2) 6 inch
pieces from one end. These will be the axles for your
wheels on the base.
Step 29
Attach one wheel to one end of
the 6 inch dowel. Secure it in
place with a drop of glue.
Slide two of the 1 inch drinking
straw pieces onto the wooden
dowel. These will be the bearings
for the wheel and axle assembly
which will allow your trebuchet to
roll smoothly when it is firing.
DO NOT glue the straws
to the dowel!!!
Attach the other wheel to the
other end of the dowel. Secure it
in place with a drop of glue.
Step 30
Attach the wheels to the
bottom of your trebuchet.
Use hot glue to secure the
straws to the bottom of the
base
Be sure to use enough glue
to completely encircle the
straw. This will prevent the
wheels from falling off
because the glue did not
hold.
Step 31
Repeat Steps 29 and 30 for
the other set of wheels and
axle, and again attach
them to the bottom of your
trebuchet.
Counterweight
Step 32
It is now time to Secure your counterweight (CW). If you
have your medicine
bottle filled with 150
pennies, you will need
to have your teacher
drill two holes into the
lid. This will facilitate
attaching it to your
throwing arm.
*NOTE*
If you can not acquire a medicine bottle, you will have to fabricate your own
CW. It is up to you to equip your trebuchet with a CW. What it looks like and
how it is made is completely up to you. Remember that it must fit within the two
sides of the trebuchet, and the total height must allow it to swing freely without
touching the platform of the trebuchet.
Determining Weight
Step 33
It is now time to start determining the weight of the pieces of
your trebuchet. Gather your throwing arm, counterweight,
and the projectile that you will throw (see your teacher for
the projectile). You will also need access to a Triple Beam
Balance.
Step 33
Weigh each of the pieces
you have gathered.
(Throwing Arm, Counterweight, and Projectile)
You will need to know these
weights later on in the project,
but if you do not gather them
now, it will be much more difficult
after the trebuchet id constructed.
Record the weight of each
in our Student Journal.
Sling
Step 34
Cut a piece of cloth that is 6
inches long and 4 inches
wide. The neater you cut
this piece, the better your
sling will work.
Note: Thin cloth works much
better than thick cloth.
Step 35
Cut two pieces of
string that are each
2 feet long. (24
inches)
Step 36
Tie the end of one
piece of the string
around one end of the
cloth.
(Do not cut the extra
off yet.)
Wind the string
around the knot about
3 times, and then tie it
off again. use a little
hot glue to make sure
that the knot does not
come undone.
Step 37
With your second 2
foot piece of string,
repeat Step 36 on
the other end of the
piece of cloth.
Step 38
Locate a plastic golf
ball (projectile) and
place it in the sling.
It should fit loosely.
Step 39
Tie one end of the sling
to the throwing arm.
Wind the string around
the knot about 3 times,
until about nine inches
of string is between the
sling and the throwing
arm. Again, use a little
hot glue where necessary to make sure that
the knot does not come
undone.
Step 40
Tie a slip knot ar loop at
opposite end of the other
piece of string.
Again, leave approximately
nine inches of string in
between the cloth and the
slip knot.
Step 41
Retrieve a paper clip and
bend one end of it straight,
as show in the top picture.
Then Bend half of the
curved portion of the paper clip up, as shown in
the bottom picture.
This paper clip is going to
be the prong at the end of
the throwing arm.
Step 42
Use hot glue to attach the
paper clip to the end of
the throwing arm (round
end out).
Be sure that you attach it
to the opposite side of the
arm as the axle.
Your sling in now complete
and attached to your
throwing arm assembly. it
should look similar to the
one in the picture.
Counterweight Attachment
Step 43
Attach the CW to the short end
of the throwing arm. Secure it
so that it does not come loose,
and does not hit the sides of the
platform of the trebuchet. This
may take some adjustment to be
sure that it moves freely. Attachment may be easier if the
throwing arm is not attached to
the trebuchet while working on
it.
Throwing Arm Attachment
Step 44
Once you have the CW attached to the
throwing arm, and the frame of the
trebuchet completed, you are ready to
put it all together. Place the axle of the
throwing arm into the top “V” on each
side of the Trebuchet frame. The
throwing arm should rest ON the axle
when you place it in the “V”. You may
secure this in place with a couple
pieces of drinking straw, or leave it as
is, if it seems secure enough. DO NOT
glue the Throwing arm axle to the
“V”s. It must move freely.
Trigger Mechanism
Step 45
It is your responsibility to create a firing pin or trigger mechanism for your trebuchet. You may not participate in destroying
the castle if your trebuchet does not have a firing pin. The purpose of the firing pin is to allow the operator to activate the
trebuchet from a safe distance. Your trebuchet must have the
same consideration. Below are a few examples of trigger
mechanisms. Study them and come up with a solution that will
work on your trebuchet.
Finished
Step 46
Your Trebuchet is Finished! You will now test
fire your trebuchet and
begin adjusting the
components of your
trebuchet to optimize
the trajectory of the
projectile.
Go Forth and Hurl Young Warrior!