This weekend Seth and I built a soda bottle water rocket.

We used a 2 liter soda bottle Just fill it about 30% with water then pump it full of air and watch it blast off.

The launcher design I used is pretty simple to make. I took a 10" long piece of black pipe, that was 1/2" in diameter. That just about matched the inside diameter of a 2 liter bottle opening. The I found a PVC elbow joint to screw it into. I got a pvc plug for the elbow joint. Drilled a hole in the pvc plug then put a car tire valve stem in the hole. I used one of the chrome valve stems because they are metal and use a nut to hold them in place. Then I put the plug into the elbow and glued it together.

My 5 year old son and I built a ping pong ball cannon this weekend. It is powered by a shop vac. It was very simple to build and lots of fun for a 5 year old to shoot.

Basically I found a piece of plastic pipe with the same diameter as a ping pong ball. Then added a T to one end. I took the hose from my shop vac and duct taped it to the T.

I first tried using the vacuum from the shop vac. I would put a piece of cardboard over the front of the tube, insert the ball into the other end and put a piece of cardboard over that end. Then turn on the vac. Once the suction was built up, I would remove one piece of cardboard. The air rushing in would force the ball down the tube out the other end (knocking the cardboard off the other end). We didn't have much luck with this route. The ball shot down with a lot of force, but when it hit the cardboard on the other end, it would loose a lot of mementum. This design is used in a lot of physics classes to demostrate the effects of air pressure. A good site describing the physics of it is here.

Sometimes it is nice to just hang out with the guys and do manly things. My friends and Iparty.

built a catapult to throw pumpkins at the company Halloween party.

We named it the "PMD", the Pumpkin of Mass Destruction. The only problem was that people kept having a hard time finding it.

It was a real team effort to build the catapult. It took us a weekend to build. We used 430 pounds of counterweight and could throw a 3 pound pumpkin up to 210 feet.

Here is what a pumpkin looks like after it has been thrown a few hundred feet. Channel 5 news came out and filmed us. They put a 10 second clip of us throwing a pumpkin on the 6 o'clock news.