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My water rocket launcher. Updated with vids

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My water rocket launcher. Updated with vids

Unread postAuthor: Insomniac » Thu Sep 11, 2008 4:53 am

A few years ago I used to fire water rockets from a hose connecter and a short bit of pipe with a shraeder valve hose clamped into the end. So, I decided to upgrade it a bit and get back into water rockets. What you see here is a bunch of pipes and fittings from my old ball valve pneumatic launcher. The ballvalve is so I can vent water and pressure from the rocket without launching if I need to. The string trigger works, but because of how strong the spring in the hose connecter is, I have to actually hold part of the launcher to get it to release (otherwise it would just slide across the ground). At least this lets me use circular fins (my hand wouldn't fit to release manually) and it lets me keep my hands off the bottle on the off chance the bottle blows apart. I have yet to actually fire the rocket in the picture, and haven't launched anything off the launcher in this configuration, but I know how well it works because it is basically a nice stand and a few valves added onto the old, handheld launcher.

The rocket is just a 1.25L soda bottle (I pressure tested it to 120 psi, will not go over 100 for actual launches) To make the nozzle, I used super strength araldite to glue a lid into an appropriately sized tap adapter. The nosecone is a bit of foam from a pool noodle I cut into a rough cone shape, and covered with tape.

The only problem with this launcher is there is no guide for the rocket for the first metre of flight, where the fins arn't effective because of the low speed. Hopefully it will go fairly straight until the fins start working, or I'll have to add some sort of guide.

Hopefully I'll get to launch it soon and will post my results (maybe even a vid). If any of you here haven't tried water rockets, I really encourage you to. They are great fun and offer the same sort of engineering challenge as spudguns (but are LEGAL in Australia!!!!) Just make sure you use bottles designed for carbonated drinks.

I don't have the parts to do this, but I would LOVE to see somone make one that fires from a tube open at both ends, fired from the shoulder. A bicycle brake cable could be used as a trigger.

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Last edited by Insomniac on Sat Sep 13, 2008 1:34 am, edited 1 time in total.
I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

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Unread postAuthor: Stifler69 » Thu Sep 11, 2008 5:19 am

Nice, looks awesome man
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Unread postAuthor: mark.f » Thu Sep 11, 2008 6:01 am

Cool! That beat's the crap out of my water rockets. They were just 20 ounce bottles with male quick-disconnects tapped into the cap.

Have you ever thought of making a rocket out of PVC and adding a piston to the inside, so that you could launch the rocket from any angle? It would require you filling in air from the top, but the same release mechanism could be used (I've always dreamed of making a 4" PVC version of this with a dust plug as this release valve...)

EDIT - I think I see DWV, though... :wink:
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Last edited by mark.f on Thu Sep 11, 2008 9:09 am, edited 1 time in total.
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Unread postAuthor: nz_cannons » Thu Sep 11, 2008 6:26 am

Used to do a lot of this stuff huh. Similar rocket using a 1.5 litre bottle. Would pump up to 120-130 regulary. Good hights achieved, easily 100 meters straight up, probably more, its been a while since I did them.

Exactly same hose connector but more ridgid base that was staked into the ground. Had some bottles explode at 145 or something, the browns ones only though, they were weaker for some reason.

I had a clear one with a half bottle nose cone that repeately got smashed when it hit the ground, we launched it 50+ times with no problems at 120 psi.

Also made some with parachutes that worked fantastically well, just a medium sized plastic one from a model rocked taped to the top of the bottle and draped over, would go up with little difference and come down nice and smooth.

Have been thinking of better ways to make the whole system actually.
Better designed rockets using aluminium struts and proper formed nose cones. Two aluminium sheet metal bits that would fit around the bottle and hold the struts.
Using a hydraulic connector instead of hose disconnect, possibly machine my own male piece with slight converge and divergance passages, hell, might make a difference, would be interesting to try anyway.

Only annoying thing is finding a good shape bottle with a large volume, 2 litres are generally a little to fat for my liking, now a thinner 2.5 litre bottle with three aluminium braces along it's length would be ideal.

Wonder how hard it would be to make some molds to form the nose cones in, I never really liked the stove top heating method.
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Unread postAuthor: daberno123 » Thu Sep 11, 2008 6:10 pm

I just recently got assigned a physics project involving this...

I had a simple launch set-up a few years ago. It was just some 1/2" PVC with a schrader on one end and a male adapter on the other. The male adapter was covered in electrical tape for a friction fit on a 2-liter bottle.

I'm going to rebuild my set-up now that I have a school project. Its to see who can get their water rocket to stay in the air the longest. I'll have a bit of an advantage since no one else will have a launcher to test their rocket at home. They'll have to bring it into school to test it. I plan on making mine stay up the longest. Shouldn't be too hard as I've built some of these before. The only tricky part will be the parachute, but I'm confident I'll find a good design for one.

Your design looks solid, make sure to update us on how it flies.
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Unread postAuthor: Insomniac » Fri Sep 12, 2008 12:48 am

Still haven't had time to fly it, but here is a great site I found on the web. Some of the videos of the 2 stage rockets are unbelieveable. Especially the onboard footage.

Does anyone here have access to pipe wide enough to fit a 600ml bottle inside with a bit of clearence? I want to see somone make a shoulder fired rocket launcher :D Surprisingly, I've found that the small 600ml bottles go really really far because of their low drag.


markfh11q wrote:EDIT - I think I see DWV, though... :wink:


Then you are wrong :wink: I forgot to mention in the first post, this is all irrigation poly pipe (not sure if you can get it in the US) Not sure what the pressure rating is, there was no info of it at the store, but it obviously is made for some pressure seeing as it is used with sprinkler valves and the like. I've tested it pretty high though, and it seems strong enough. I'm pretty sure the soda bottle would burst first.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: Insomniac » Sat Sep 13, 2008 1:33 am

Finally got to launch it today. The first launch I didn't get on camera, and it ended up breaking off the fin somehow. So I made a different set of fins and we drove out to a large field to get some footage of it launching. The bottle was in pretty bad shape after 3 launches so we decided not to risk putting it under pressure any more and went home. Hopefully I can figure out a simple way to deploy a parachute so the rocket doesn't get crushed from impact.

[youtube]http://www.youtube.com/watch?v=ECEcJG9ugDM[/youtube]
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: jimmy101 » Sat Sep 13, 2008 10:21 am

It doesn't look like you have a launch tube, right? A launch tube reaches up into the bottle nearly it's entire length. The tube is usually sealed with an O-ring or two and really helps to keep the rocket straight during launch. 1/2" SCH40 PVC is nearly a perfect fit in the neck of most plastic soda bottles, the O-ring gives a seal good to at least 120 PSIG.

You might want to consider making a "Clark Cable Launcher" instead of the quick connect based one you have now; http://www.cullytechnologies.com/demo/h ... kcable.php
http://homepage.ntlworld.com/telescope/ ... uncher.htm
http://www.smoke.com.au/~ic/cable-tie.html
They aren't nearly as hard to build as they look from the instructions.

One simple way to do a chute, that usually works, is to just drape it over the nose of the rocket. A pin at the rocket nose through an inch or so diameter hole in the center of the chute will help to hold the chute in place. And, the hole in the chute makes the chute work better.

Another simle thing to slow the fall is a "ping-pong ball" tumble recovery. Not nearly as pretty as a chute but a lot simpler. Just add a carboard tube 1 to 1.5X as long as the bottle to the nose. Connect a pingppong ball to a string that is about the length of the rocket, tie the other end to the tube. At apogee the pingpong ball falls off and destroys the aerodynamics of the rocket. If the string is the right length the rocket will return to the ground horziontally and relatively slowly. http://catalog.pitsco.com/store/detail. ... =1&t=0&l=0
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Unread postAuthor: Insomniac » Sat Sep 13, 2008 7:12 pm

Yeah I already knew about launch tubes and cable tie launchers, but I like the hose connecter version better simply because it gives more thust for longer, and it is much easer to adjust the nozzle size with a screw-on nozzle. I may use some sort of guide rail to help keep the rocket going straight at launch, similar to what they use for model rockets (although this won't give the initial 'boost' of a launch tube). I might try the drape-over-nose type parachute some time, but unfortunately that method makes a lot of drag on the way up, which isn't exactly ideal. I might make a tomy-timer parachute recovery system if I can get it light enough. Either that or just use 600ml bottles that are reinforced so landing doesn't break them.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: knappengineering » Sat Sep 13, 2008 9:14 pm

Just make a plastic nose-cone from another bottle or a plastic/paper cup. Attach the parachute to the bottle and pack loosely into the nose cone. Then when the rocket reaches the apogee the nose cone should fall off and the parachute should deploy if packed correctly. Add a little weight to the tip of the nose cone if needed.
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Unread postAuthor: Insomniac » Sat Sep 13, 2008 11:47 pm

I've tried that, but it doesn't work if the rocket doesn't go straight up and tip at apogee. So to get that working well the launcher will need a guide rail of some kind.
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: jimmy101 » Mon Sep 15, 2008 10:58 am

Insomniac wrote:... but I like the hose connecter version better simply because it gives more thust for longer,

How? I believe the smaller nozzle gives less thrust for longer time. Less thrust for a longer time is OK except the slow acceleration means it takes a while to get enough velocity for the fins to have an affect. The smaller nozzle gives higher exhaust velocity at the expense of exhaust mass. I believe you are mostly concerened with momentum in this setup so a larger nozzle gives higher mass flow at lower velocity, the smaller gives lower mass flow at higher velocity. The thrust time is also different but I believe it works out to be a push, there is no significant advantage to one size nozzle versus another during the major boost phase. (There is an advantage to a smaller nozzle when you are ejecting just air and not water.)

Insomniac wrote: and it is much easer to adjust the nozzle size with a screw-on nozzle.
But doesn't the screw on nozzle have to match the garden hose quick-connect? In other words, it could be changed if you can actually find different quick connect sizes.

Insomniac wrote:I might try the drape-over-nose type parachute some time, but unfortunately that method makes a lot of drag on the way up, which isn't exactly ideal.

I wouldn't thhink the draped chute would add a significant amount of drag. The radius of the chute probably only needs to be about the same as the length of the rocket. So the draped chute is basically the same size and shape as the rocket. The drag caused by the chute's cords really shouldn't be significant.

Insomniac wrote:I might make a tomy-timer parachute recovery system if I can get it light enough. Either that or just use 600ml bottles that are reinforced so landing doesn't break them.

Tomy timers are pretty neat systems but kind of tricky to get'm to work. You might also consider just using an air flap system instead of the timer. Air flaps are pretty simple though they do tend to release a bit before apogee. The ping-pong ball system is really the simplest recovery system.
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Unread postAuthor: Insomniac » Tue Sep 16, 2008 1:05 am

Yeah that was a typo, I meant less thrust for longer which I think looks more rocket-like, as opposed to the cable tie launchers that just sorta go POW!, whereas the hose connect type look more like a normal rocket.

The nozzle is really easy to adjust to any size up to the size of the hose connecter. I just put a plastic disk with a hole in it in the lid, and the hole acts as the nozzle. I obviously can't go any higher than the size of the hose connecter nozzle unless I find a larger hose connecter (I've seen them before, but not at the hardware store)

As for the chute, I haven't tried the drape method yet, but most websites I've visited that mention it say that the rocket doesn't go nearly as high. Maybe because the chute flaps around and doesn't stay pressed against the nose, or maybe they were using a really big chute.

I've also tried tomy timers before, I managed to get one to work but the setup I had was pretty dodgy and heavy, not exacltly ideal. The next rocket I make will probably just be a small, strong bottle with the fin spars running the full length of the rocket to strenghten it. It should be able to land without getting too damaged, as the wooden spars should transfer the momentum of the fins and spars directly to the nose, bypassing the bottle. The bottles tend to crumple near the front from the momentum of the fins, so this should protect the bottle pretty well. All it will have to deal with will be it's own weight, and the momentum of the nozzle.
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Last edited by Insomniac on Tue Sep 16, 2008 6:37 am, edited 1 time in total.
I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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Unread postAuthor: Sticky_Tape » Tue Sep 16, 2008 5:09 am

I used to make water rockets this is my rocket
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Unread postAuthor: Insomniac » Tue Sep 16, 2008 6:34 am

Very nice! Roughly how high does that one go? Is it stable in flight? What sort of parachute system do you use?
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I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
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