Thanks a ton for the kind words on the project I love your mods and your write-up on the blog was fantastic. We’re on a road trip across the US and I wish Charlotte was on our route so I could visit your local hacker space. All the best to you and all the folks there!

- Rick

http://slackaliciousme.blogspot.com/2012/07/compressed-air-rockets.html

It should be said that for our launchers we use screw in schrader valves which can handle considerably more pressure than tire valve stems. Valve stems are rated for 65psi or possible 110psi if they’re the “high pressure” (much more rare) variety. Home Depot has the valve stems online for only $1.49!! Shipping will kill you unless you’re ordering in bulk though. Grainger also has them for $3.04 each. Failing that Ace Hardware usually keeps a couple in stock, but they’re $5, and the brass busing to get from the 1/8″ threads on the schrader valve to the 1/2″ pvc threads costs another $3-$4 from just about any hardware store.

I would like to hear more as you look into a wireless launch system. Right now, as a safety precaution, I hold the launch button while putting the rocket on the launch tube. I’ve had the rocket launched in my hand a couple of times so now I always hold the button. Thanks for posting your thoughts.

Cheers,

Rick

We do these a the middle school where I teach as well! Thanks for posting your ideas.

- Rick

Good ideas. I use a small rechargeable compressor for local park launches and my big compressor for large events like Maker Faire. With the large compressor, it automatically recharges after every launch, which is good because we often do 2000-3000 a day!

- Rick

Thanks so much for responding to the post. I’m glad you’ve had such a good time with this project. It seems I’ve been spending so much time launching that I haven’t taken the time to work on mods. I’m especially interested in ideas for deploying a recovery system. I would LOVE to see some pics of some of the work you’ve done.

In September we’re doing a night launch with LED’s at the local children’s museum. Should be fun. I appreciated your testing at higher pressures. I’ve always believed this to be safe project if common sense is used. I think at the usual 75 psi, you are well below the tolerances of the PVC. I’m sure the valve would blow or tubing before the PVC went. Again, I would love to see some pics and thanks again for posting your mods.

Cheers,

Rick Schertle

I want to hear more, especially on the heli-recovery. I’ve also been looking into simple ways to deploy a parachute. With a recovery system, all kinds of opportunities open up like launching small video camera. Glad you’re enjoyed the project so much!

Cheers,

Rick

The best rockets we have use regular paper. Enlarge a 1/2″ piece of pipe with few extra layers of tape. Then roll a whole sheet a paper (no need to cut anything) around the tube and tape. The tape makes all the difference. We use clear packing take. It’s light, it’s slick, and it’s strong. As an added bonus if the kids want to decorate their rockets they can do that first and then you can coat with tape. We’ve launched these rockets at unsafe pressure (150+ lbs ) just to test the limits. They don’t fail. The fins are made of only packing tape (or occasionally a business card). We just fold about an inch of the tape on itself and stick the rest to the rocket. Then we cut the leading edge of the fin (lest you get erratic flight when the fins bend over at the leading edge). We put three of those on in less than a minute. We often skip the nose cone altogether – just cap the tube with 4 layers of tape (no paper disc).

That’s our basic rocket that we make in easily less than 5 minutes that will last until lost. But we have some popular mods:
— LEDs taped to outside
— stuff an LED inside towards the nose cone… since it’s clear tape
— glow sticks on the outside
— electrical tape for nose weight
— one angled fin for spin
— a streamer stuffed inside for a delayed deployment (we’re working on getting that as a drone for parachute)

I recently went the other way with testing… I took my kids out to test the effects of changing the volume of the compressed air storage chamber at a variety of pressures with rockets of differing weights. We even wrote done our results so we can call it science! The short answer is, for manual control (human at the switch) a relatively small volume (15 inches of 1″ tube) is sufficient for decent range ( 200-300 feet at 20 degree launch angle). We’re (the Hackerspace) working on an arduino controlled fire control system to for this years Fourth of July Fabulous Fireless Fireworks Display. Essentially we suspect we don’t need the valve to stay open very long to launch a rocket, so we can close it before we lose a lot of pressure. That will allow for more launches (those compressors have a hard time keeping up).

And speaking of fireless fireworks… We swap the 1/2″ pvc launch tube for a 1.25″ tube and load in glow sticks/bracelets (the 15 for $1 kind a Michael’s or Target). Wadding (paper towel) is required to keep the air from rushing around the sticks, and in between each layer. We typically have three layers of 25 sticks in each tube and launch at about 75lbs psi for 100′ vertical launches. If we wrap the 25 stick bundles in a paper towel they stay together longer and will go higher. Streamers on the glow sticks sort of work, but it’s not worth the effort. Those same glow sticks tape nicely to the outside of rockets too (remember, clear packing tape) and go insanely high – but they’re much easier to track at night. LED’s are even brighter – and very cool if you put different colors on one rocket and have it twist… or have some point up and some down – you see different colors on the way back down.

Our launchers have evolved quite a bit into very efficient, compact and cost effective models. I’ve build about 10 now with no two being the same, and some wildly different. I’ll see if I can’t get around to posing pictures and test data (and maybe some arduino code) up on the hackerspacecharlotte.org website before too long.