Heavy-duty wood-frame rocket launcher

[Little-Acorn]

Cub Scout Pack 629 in San Diego, CA had a campout last weekend (May 23-25, 2014), and one of the featured activities was Water Bottle Rocket launching! After looking through the various launchers here, on eBay, and elsewhere, I designed a new one, built two copies, and a good time was had by all.

Most launchers I'd seen up till now, are built mostly from PVC pipes of various diameter, and many use a circle of tie-wraps in a clamp to hold down the rocket while it's being pumped up. Some take a heft yank on the launch string, and then seem prone to tipping over, pointing the rocket straight at you Others have the air valve right on the launcher itself, meaning you have to stand right next to the bottle as you pump it up. One slight crack in a well-used bottle, and you get a big surprise, and possibly worse. Yet others have a lot of fairly large-diameter tubes joine together, which must ALL be pressurized to pump up the rocket. You wind up pumping three or four times as much air as the rocket itself needs, to pressurize the whole thing.

We tried to avoid most of these problems with this design. It's a heavier wood frame made from 1x6's that sits low and long. Uses a steel-rod "hairpin" to lock the rocket while pumping to avoid the alignment and fragility problems of the tie-wraps in the Clark-type launcher. A small aluminum piece clamps the ends of the hairpin lock together, very easy to pull off with a string, you don't need a huge heave. The air hose is 25 feet long (as is the trigger string), but only 1/4" outside diameter (0.017" inside), so has minimal volume that must be pumped up, only about a tenth of the volume of a 2-liter soda bottle. If the bottle goes boom while you're pumping, you're 25 feet away.

Drew up a parts list and instructions for building the thing, it's not too complex. I've attached the document here, hope it comes out OK.

The launcher is adjustable where it needs to be - you can raise the lock up or down by adding fender washers under it, the launch tube can be raised or lowered by putting a different-length pipe nipple in the flange base. Have a look at the instructions, you'll see how it goes.

Nearly all parts are from Home Depot, their SKU numbers are in the parts list, and current prices. A tire valve is from NAPA Auto Parts, and a few other pieces are from the local hobby shop, pretty common.

If somebody builds this, can you let me know how it goes? How understandable ar the instructions, how well does the launcher work, any suggestions etc.?

Hope I didn't mess it up too bad!

[Jamie5335]

Hello,

It is clear that you have put alot of time and effort into this design and that has really paid of. It is also nice to see new designs and well as the infamous Gardena and Cable tie launchers.

A video of the launches would be great as well.

My only concern is that because you are launching rockets with a 22mm nozzle, they accelerate very quickly. As long as the metal lock gets out of the way quick enough for the rocket to slip through that would be fine. Have you tested it?

Cheers, Jamie B.

[bugwubber]

Excellent job on the instructions. It takes a lot of effort to put your own ideas on paper for others to understand. The release mechanism is nice and simple and looks like it will take a lot of abuse. I'd say you need some fold out "outriggers" for side stability as well, but this is coming from a guy whose rocket launcher base is 5'x4'. ;-)

[Little-Acorn]

It is clear that you have put alot of time and effort into this design and that has really paid of. It is also nice to see new designs and well as the infamous Gardena and Cable tie launchers.

Thank you kind sir. The proof of the pudding is in the eating - I hope someone tries building and using this, maybe they can let me know how well the instructions and parts list coincide with reality.

What is a "Gardena" launcher? Sorry, I'm new here, not familiar with that one. My apologies if it's commonly known to everyone else.

A video of the launches would be great as well.

Might get one at the upcoming Cub Scout Roundup tomorrow at Hilltop Park. Rocket launches galore!

My only concern is that because you are launching rockets with a 22mm nozzle, they accelerate very quickly.

That's not a bug, it's a feature. What's wrong with quick acceleration?

As long as the metal lock gets out of the way quick enough for the rocket to slip through that would be fine.

There's no acceleration until the lock prongs are out of the way.

Have you tested it?

Cheers, Jamie B.

About a hundred times at the Scout campout last weekend. Lots of glorious flights! You know you've got a satisfactory launcher, when nobody notices it's there. Everyone watches the rockets fly and has a great time, no one cares about the launcher... unless it malfunctions.

We wore out an O-ring about halfway thru, it wouldn't stop leaking. Replaced the O-ring and the leaks stopped, and everything was great for the rest of the afternoon.

Excellent job on the instructions. It takes a lot of effort to put your own ideas on paper for others to understand.

Thank you! I tried to write them up so that any family in the Cub Scout Pack could take the parts list to Home Depot etc. and get everything without hassle, and could then clear off their home workbench and build it with a few hand tools, ditto.

The release mechanism is nice and simple and looks like it will take a lot of abuse.

That was the idea. Toys used by 8-year-olds tend to take a terrific beating. I wanted it to be easy to use and keep performing with no hassles. KISS. So far so good.

I'd say you need some fold out "outriggers" for side stability as well, but this is coming from a guy whose rocket launcher base is 5'x4'. ;-)

Thought about that, I figured to simply bolt another 1x6 piece on the bottom at one end at a right angle, flat, to make a T shape. But then the launcher wouldn't sit quite flat and need extra shimming with a handy rock, reducing stability. Might use 2 boards to form an uppercase I, then it becomes more awkward to put in the car etc. It's always a tradeoff, again KISS. Haven't had any stability problems so far, though. I can always add those other pieces later, maybe make them swivel, etc.

Onward and upward!

[U.S. Water Rockets1]

You should give some thought to adding our split collar cable tie launcher design to this launcher. It reduces the effort needed to launch the rocket, which makes it a lot easier for the kids to pull the release and safer because the launcher is less likely to move when pulling the release with our design. Other than that, it looks like a good design.

[Little-Acorn]

You should give some thought to adding our split collar cable tie launcher design to this launcher. It reduces the effort needed to launch the rocket, which makes it a lot easier for the kids to pull the release and safer because the launcher is less likely to move when pulling the release with our design. Other than that, it looks like a good design.

Thank you kind sir! I need all the feedback I can get.

Did you build this wood-frame one and try it, and find it hard to pull the string to launch? That was something I was trying to improve on. It's important to clean up the ends of the prongs of the V-shaped lock with a file in this design. Then the aluminum trigger piece slips off quite easily. I don't know if I mentioned that in the instructions, I'll have to check. I've got 7-year-old kids launching rockets at 80psi by looping the string around one finger and pulling with that. And yesterday at our Cub Scout Roundup picnic someone's three-year-old daughter launched one twice, though I think she just held the string in one hand. She put the other hand over her eyes, couldn't get her to stop doing that, she missed all the fun.

Hmmm... maybe if I slip a nylon tube over the lock guide? Might make the prongs of the lock move sideways more easily?

Thanks for the suggestions!

[ptx]

Nice launcher!

[Water Rocket Expert]

I only briefly looked at the instructions; they look fine. What camera did you use? Otherwise, a video of some sort would help with determining if it is good or not. Looks like a cool design though. Did you create it?