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Off-Topic Discussion => General Discussion => Topic started by: captain-custard on October 11, 2008, 02:16:38 pm

Title: water rockets
Post by: captain-custard on October 11, 2008, 02:16:38 pm
just a question any one here ever tried building flying exploding water rockets?
Title: Re: water rockets
Post by: Shade on October 11, 2008, 02:27:40 pm
Exploding? No. But the flying part is easy, just get a plastic bottle, a pump (bicycle pump will do nicely), some plastic hose (so you can keep a safe distance... not to avoid getting hurt so much as to avoid getting soaking wet), a one-way valve and something to seal the bottle with that'll come loose at a high enough pressure and has a hole in it that'll fit the hose.

Cut the hose into a short bit and a long bit. Fill the bottle with water to about 1/5th capacity. Seal it around one end of the short bit of hose and attach the exit end of the valve to the other end of said hose. Attach long end of hose to the entry end of the valve, and cap it all off with the bicycle pump. Now just get the bottle pointing upwards, retreat to a safe distance, and start pumping :)

Did this in physics class in school a few times :D

[Edit] For added coolness, add a pigment to the water. If you do this though, use something harmless instead of swiping stuff like potassium permanganate from the local chemistry lab for its cool purple, because the water *will* get sprayed everywhere and you really don't want anything remotely toxic in it.
Title: Re: water rockets
Post by: Herra Tohtori on October 11, 2008, 02:31:45 pm
I thought the main point in rockets was that they don't preferably explode. That's for missiles.

Water rockets are based on using compressed gas (usually air, though other gases can be used as well) for storing energy and water as propellant. When the pressure pushes the water out of the bottle, the rocket gains momentum to opposite direction. The only thing that can explode in this device is the pressure vessel, and it is a hopefully avoidable occurrence rather than desireable.

So I don't really get what you mean by "exploding" water rocket... :nervous:
Title: Re: water rockets
Post by: captain-custard on October 11, 2008, 02:35:59 pm
ive done most of that and today i built two cable tie launchers and am able to get small 0.5 litre bottles up to about 9 bar and larger bottles 1 to 2 litres up to 8 bar , i was just wondering if anyone has managed to go really high , i guess im going between 50 and 60 metres straight up ,
there you go but i must say its a good laugh and my son just loves launching , me i m good for an hour or so then i get bored of pumping ,
Quote from: Herra Tohtori on October 11, 2008, 02:31:45 pm
I thought the main point in rockets was that they don't preferably explode. That's for missiles.

Water rockets are based on using compressed gas (usually air, though other gases can be used as well) for storing energy and water as propellant. When the pressure pushes the water out of the bottle, the rocket gains momentum to opposite direction. The only thing that can explode in this device is the pressure vessel, and it is a hopefully avoidable occurrence rather than desireable.

So I don't really get what you mean by "exploding" water rocket... :nervous:


i now know that coke bottles explode at around 10 bar,one did today i got wet and my ear drums rattled ,  :eek2:
Title: Re: water rockets
Post by: Mobius on October 11, 2008, 02:40:15 pm
Quote from: andicirk on October 11, 2008, 02:35:59 pm
i now know that coke bottles explode at around 10 bar,one did today i got wet and my ear drums rattled ,  :eek2:

It happened to one of my classmates 6-7 years ago...it was unexpected... :lol:
Title: Re: water rockets
Post by: Solatar on October 11, 2008, 07:04:50 pm
I did some of this in middle school years back. It was a lot of fun.

Potato guns are fun too, but a little bit more dangerous. I had a friend whose dad was a dentist and he somehow got ahold of pure oxygen to play with.
Title: Re: water rockets
Post by: Androgeos Exeunt on October 12, 2008, 10:17:47 pm
Potato guns? Hmm...I once saw Jeremy Clarkson make one from pipe, a gas lighter, and hairspray.
Title: Re: water rockets
Post by: Colonol Dekker on October 13, 2008, 06:42:52 am
We've all done that, I was tought by How-2 on citv :D
Title: Re: water rockets
Post by: Excalibur on October 13, 2008, 07:42:58 pm
Hmmm... :drevil: attach people's keys and things for the ride...

Experiment with different amounts of water, make a nose cone and fins. Get the strongest plastic bottle that is light as well.
Title: Re: water rockets
Post by: watsisname on October 13, 2008, 08:14:36 pm
You should swap the water with some liquid N.  :drevil:
Title: Re: water rockets
Post by: S-99 on October 14, 2008, 06:56:57 pm
Quote from: Solatar on October 11, 2008, 07:04:50 pm
Potato guns are fun too, but a little bit more dangerous. I had a friend whose dad was a dentist and he somehow got ahold of pure oxygen to play with.
You took the recommendation right out of my mouth. Always be responsible with them, that's about the best anyone could do. Hairspray really mungs up a potato gun though. I recomend starting fluid (it's after byproduct is just water vapor) and gasoline. Both will keep your potato gun pristine and in working order without needing to clean the hairspray after byproduct which is slime which will make your barbecue lighter or flint lighter not work real fast. Also gasoline and starting fluid is a lot more powerful than hairspray also not requiring so much to be sprayed into the blast chamber compared with hairspray. Propane works pretty good too, you have to shop around for a suitable propane feeder for the gun though.

Quote from: andicirk on October 11, 2008, 02:35:59 pm
i now know that coke bottles explode at around 10 bar,one did today i got wet and my ear drums rattled ,  :eek2:
See if you can get past 10 bar with a coke bottle if you reinforce the bottle's structural integrity by wrapping it up in lots of duct tape very tightly. If you are looking for something stronger, you could try small glass root beer bottles. I'm pretty sure they hold more pressure than plastic would. Get behind a blast shield or course to see how much pressure it takes a glass bottle to explode :yes:


Title: Re: water rockets
Post by: Excalibur on October 14, 2008, 09:38:10 pm
Get a strong rubber stopper too, or else you'll never find out...
Title: Re: water rockets
Post by: Admiral_Stones on October 15, 2008, 04:40:49 am
You could form your own bottle made of kevlar... and instead of water, you combine gasoline with a small detonator. Would be teh awesome, if you can make it work.
Title: Re: water rockets
Post by: Excalibur on October 16, 2008, 09:28:09 pm
Re-inforced petrol bomb...
Title: Re: water rockets
Post by: Mobius on October 17, 2008, 04:55:27 am
Quote from: watsisname on October 13, 2008, 08:14:36 pm
You should swap the water with some liquid N.  :drevil:

I can steal a small tank of liquid N from one of the Uni labs :drevil:
Title: Re: water rockets
Post by: Androgeos Exeunt on October 17, 2008, 07:45:06 am
Quote from: Mobius on October 17, 2008, 04:55:27 am
I can steal a small tank of liquid N from one of the Uni labs :drevil:

<< WARNING: SEVERE DANGER >>
Title: Re: water rockets
Post by: S-99 on October 17, 2008, 11:43:54 pm
Reminds me of strange wilderness.
Title: Re: water rockets
Post by: Mobius on October 19, 2008, 06:56:53 am
Don't worry, I can't do that...I'm a pretty honest person...

...hehe... :drevil: