There were a few motivations for this project. I started my new job here at Digilent, and for the first time ever I have a desk. And co-workers. This sparked a new passion I never knew I had in me before: small-scale, office-supplies-built, warfare. I had quite a bit of trouble deciding between a desk mounted nerf-gun, ping pong ball gun or an auto-tracking trebuchet.
Naturally, I went with the auto-tracking trebuchet. What else am I supposed to do with old post-it notes besides crumple them up and launch them at fellow interns? Throw them in the trash? Yea, right.
This is more or less the poor-man's trebuchet. But below the depths of popsicle sticks and fairly-poor hot-glue-gunning, there's a heart. And by heart I mean (supplies list):
24 popsicle sticks
1 GW Servo (S03N STD)
2 washers (diameter big enough for pencil)
1 hot glue gun
3-4 hot glue gun glue sticks
A bread board (unless you are O.K. with your WF32 looking like a birds nest)
Step 1: The Skeleton
I started with grabbing a big handful of popsicle sticks, but I only ended up using 24.
Start with 8 sticks:
Hot glue the popsicle sticks together in pairs of two so you end up with 4 sets of 2 (maaath). Lay three popsicle sticks, evenly spaced and vertical on top of the pairs and glue them there.
Take four more sticks, lay them opposite to the ones you just glued, space them out evenly and glue away.
Then find those two washers and grab four more popsicle sticks. Glue the side of one washer to the top face of one popsicle stick. Make sure to pile on the glue, it needs to be held pretty tight. Take another stick and glue the top face of it to the other side of the washer so the two sticks form a 45 degree angle (approximately, I just eyeballed it).
Do the same procedure with the second set of sticks and your remaining washer. Glue each set to the opposite ends of your base (what we made earlier) so they are standing vertically across from each other. This is where we'll put the axle (our fancy pencil).
Step 2: The Brawn!
Now we need a launcher.
Glue two popsicle sticks together, side by side, like we did earlier. Then place a single stick in the center of the two, with about 3/4 of it hanging below the pair and glue.
I destructively broke the ends off (~1" in length) of three separate sticks. Glued two together, side by side. Then glued the other four vertical along the edges. Voila! We now have a projectile box. Glue this to the end of your 3 stick trio on the end of the pair.
Now, glue this little contraption to the center of your pencil.
Then, place said pencil through both washers on your base. Now we have something that resembles a..sling shot or something.
Step 3: Making the Base Swivel
We can use a servo to make the base swivel.
Using the WF32 and labVIEW, I programmed the servo to run with the 5V output of the WF32. The code I used is above, and there are also a ton of great examples if you go into labVIEW --> Help --> Find Examples --> Search LINX --> select any of the Servo control .vi's to help you power your servo.
Drill a hole (I used a 3/16 drill bit) in the very center of your base.
Simply place your base on the servo head (the fit should be snug) and deploy your labVIEW code. Viola...again!
Your trebuchet now swivels. But it still doesn't shoot. Part 2, coming soon!