Stupid is as Stupid does

by pittcaleb Email    1975 views

So a few years ago I took the basic design for a marshmallow shooter and made it pneumatic. You pumped air into a small compression chamber, loaded it with a marshmallow then threw open a ball valve. I could hurl a marshmallow 50' and leave a welt in the side of a teenager or dent some drywall hanging in my garage during testing. Quite cool!

So in the past few weeks, I have designed and built a pneumatic snow ball cannon. Two things I have learned in this process:

1) PVC pipe, using standard PVC glue, is not meant to hold pressure
2) Said pressure maximum, determined after multiple failures, is right around 67 PSI

As I was pumping up our version 2.0 of the cannon today, I said, and this is a transcript of me talking to my nearly 8 year old son, "Don't come over here while I'm..." [BOOM]

I had been using a good bicycle hand pump with a pressure gauge attached. It was between 60 & 70 PSI when it blew. Thankfully it only hurt my hand a little as I was holding onto it at the time.

I had glued this piece up outside in the cold, so after cleaning and re-gluing, I took it inside to set for a bit while we made more snowballs to hurl.

After a bit, we tested again. 40 PSI didn't do much more than toss the snow out of the end of the gun. 50 PSI got us 35' of throw. I slowly pumped it up to 60 PSI. The first shot at 60 got us 66' distance. Nice, but "slow" nothing fierce, but it did cover the distance nicely - out into the street even!

I pushed it a bit more to 65 PSI. The first shot was a dud. The second was good, but just shy of the 66' record. In what would be our last shot of this cannon, I eeked the pressure up to 70 PSI. It held as I loaded the snowball into the breach of the cannon. I raised the device as Josh hide on the side of the house, fearing for his life. Just as I grabbed the valve to fire, it exploded in my arms.

Thankfully I was uninjured! I just bought a new (smart) phone last week and it's a bit more complicated, for a child, than a regular cell phone. We're also considering dropping our landline which is easy for said child to call 911 with. After these near-misses, Josh and I ran a couple of "emergency drills" as to what he would do, ensuring he knew how to unlock and use my phone to dial 911, how to call mom using the built in phone book, which neighbors to go to, etc.

Ahhh, the bonding moments of building cannons, watching them explode in dad's arms, dialing 911 - it's moments like these that we'll reminisce about when we're older will be told at my memorial service.

Note to readers: Don't go over 60 PSI with PVC pipe! It's not meant to handle pressure!