Golf Ball Catapult

Are siege engines your thing? Do you love flinging things at high velocities? Well, then, this is the build for you! In this Instructable, you can learn how to build a Golf Ball Catapult with interchangeable arms that can shoot golf balls up to 80 feet! Just be careful, though! This build requires intermediate shop skills and a whole lotta' common sense. All right, let's get building now!

Step 1: Materials & Tools

To build your own golf ball catapult, you'll need quite a few materials that are very cheap and basic hand tools, and chances are you'll have some of them lying around the house.

Materials:

• (10') 3/4'' PVC Pipe
• (1) 3/4'' PVC End Cap
• (1) Bottle Cap
• (1) 5/16''x3'' Coarse Partially Threaded Bolt w/nut
• (2'x2') 3/4'' Plywood
• (1) Golf Ball
• (1) 5-pound Brick
• (5 1/2'') 5/16'' Wooden Dowel
• (2) 5/16'' Metal Fender Washers
• (16) 1/2'' Small Wood Screws
• (4) 2 1/2'' Corner Braces

Tools:

• (1) Jigsaw w/ coarse blade
• (1) Drill w/ 5/16'' bit
• (1) Screwdriver
• (1) Bottle Wood glue
• (1) Bottle Super glue
• (1) Coping Saw

Step 2: Arms

I wanted to have arms of different lengths because I made this for a science fair project. For the lengths, cut the 3/4'' PVC pipe to lengths of 24'', 28'', 32'', and 36''. Then, drill a 5/16'' hole all the way through each of the arms exactly 6'' from an end of the arm. This is where the fulcrum will be. Then, on the PVC end cap, use a quarter-sized blob of Super glue to secure the bottle cap to it. Slide the PVC end cap onto the arm of your choice.

Step 3: Arm Supports

Cut the arm supports as shown. The only parts you need to cut are the arm supports. Cut off a bit of triangular excess, and the remnant is the base of the trebuchet - exactly 1'x2'. Drill a hole for the arm bolt as shown, with a 5/16'' bit. Once you've done that, you can test fit the arm and washers by layering them as shown. Once you put the other arm support on the other side, it should look like the final picture.

Step 4: Attachment & Base

Attach the arm supports as shown with corner braces and screws. Make sure that the arm can still swing freely with no resistance. Then drill a 1/2'' deep hole 2'' from the back and 6'' from each side below the arm and glue in the dowel. Let it dry for 4 hours.

Step 5: Counterweight

This catapult is going to be fired with a counterweight, so grab the 5 pound brick. Lift it up to 3', center it over the arm, and...

Step 6: Siege

To start world domination with your catapult, always go through this checklist before firing:

1. Arm laid back
2. Golf Ball loaded
3. Counterweight at proper height
4. Launch area free of animals and/or people

Once you've finished the boring part, just drop the brick and enjoy the smooth, long trajectory of the ball and arm. Thanks for your time reading this Instructable! I hope you enjoyed it. It was my biggest build I have ever done, and I have to admit, it was pretty awesome! Just a final note - if you do build this, be careful! During an early test when I didn't understand the power of this baby, I woke up 7 minutes later after having a dream that mikesaurus hit me on the head with a baseball bat. If you do build this, leave a comment and some pictures, too! I'd love to see how you did this. Just one last thought - this is great for defending your home from burglars! I currently have this positioned at my bedroom door, just in case. Well, thanks for your time!

Comments

[tomatoskins]

HA I love your unconventional "grab the 5 pound brick. Lift it up to 3', center it over the arm" technique! Just thinking about that I can really see how easily it could feel like you were getting hit with a baseball bat. Great idea and exicution!

[Fission Chips]

Thanks!

[FabiP]

How high did it launch? The goal of my project is to fire at 10 meters from football goal and go over it (about 10 feet) and then land 10 meters away from it. Basically the golf ball will be the field goal and must land 10 meters from goal after crossing. thanks

[eruger]

Nice work on this piece and on the Instructable! One precaution: PVC (and ABS too) will work-harden when repeated flexed, vibrated or otherwise stressed over and over. So, you should probably add a 3-4 layers of duct tape to the arm (each layer in a different direction) so that if/when the arm eventually fails, shards of plastic don't go flying off at fairly high speed. This would also be a good idea for a wooden arm, although at this scale, I would use rattan wrapped in layers duct tape, just like a medieval re-enactor's sword.

[Fission Chips]

Yeah! That's a great idea for long-term use, however, I plan to only use this for 24 launches on each arm - it's for a science fair project. But thanks for pointing that out!

[eruger]

No prob. Might be a good idea to tape it anyways. When you explain that it's for safety, and how the elastic stresses in the arm could make the fragments fly off with a fair amount of force, it should win you some brownie points. Also, you can never be sure just how long that pipe has been sitting around, possibly exposed to sunlight which can also degrade it, before you purchased it. It's a little over-the-top for the short run sure, but a proper safety mentality should be a little over-the-top. If you do, you might also add some more fender washers on either side of the pivot to keep the tape from rubbing. I just hope they don't make you trade the golf balls for ping-pong balls or something.

[Fission Chips]

Thanks so much for your suggestion! Afterwards, I was playing around with the catapult, and the end of the arm shattered. I wasn't hurt, but my best pants got ripped! Waah. I should have taken your precaution! Thanks so much for it, though.

[eruger]

Bummer about the pants. Glad no worse damage was done! How did the demo go?

[Fission Chips]

UPDATE: For those of you wishing to build this, I did my Science Fair experiment and found that the 24'' arm works best. Happy catapulting!

[Ryan Hebron]

Great job on this 'ible. However, I must inform you this is technically not a trebuchet, but a catapult. The difference being a trebuchet has a pouch that the ball is released from where as a catapult has the projectile sit in a cup or sling.

http://jarodsforge.blogspot.com/2008/08/whats-diff...

[eruger]

Actually, there's a lot of debate on that, owing largely to the fact that siege engines have a history crossing many millennia and many languages. Some would even argue that a 'trebuchet' is one form of 'catapult'. Others draw the lines along the source of the power, whether counterweight or torsion. Honestly, I don't see that it really matters, when there is a clear description of how the device works.