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| DYI |
 Posted: 05/15/2008 16:29 PM Post subject: |
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Rear Brigadier
Joined: 07 Jul 2007
Posts: 2216
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You won't be able to propel a car very well with a simple water rocket. The thrust:weight ratio is too low, even if you're using materials like carbon fiber.
And I've come up with a decent design for the flash steam rocket that I'll post in the Off-Topic discussion.
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| igpay |
| Posted: 05/15/2008 17:21 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
Posts: 88
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DYI,
Even 5 rockets? How many rockets do you think would be needed to propel it?
Oh, and i cant wait to see your design for the flash steam rocket! 
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| STHORNE |
| Posted: 05/15/2008 17:23 PM Post subject: |
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Master of Spuds
Joined: 14 Feb 2007
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| probably about 25-30 in my opinion. You should do some testing to see the maximum weight 1 bottle can propel, so we know what we're working with.
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| igpay |
| Posted: 05/15/2008 17:26 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
Posts: 88
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ok, I'll try it, and i'll use a pneumatic.
Which reminds me, i'm thinking of doing it so that all rockets are connected to the same nozzle. Can a single pneumatic support 20-30 rockets at 100 psi?
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| STHORNE |
| Posted: 05/15/2008 17:30 PM Post subject: |
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Master of Spuds
Joined: 14 Feb 2007
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| igpay wrote: | | Can a single pneumatic support 20-30 rockets at 100 psi? |
Single pneumatic what? Pneumatic is a descriptive word for something that is air-powered. So I'm afraid I don't understand what you mean by that.
As far as all of them being actuated at the same time, look into sprinkler valves. There are a few ways you can modify them to have multiple valves release at the same time.
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| igpay |
| Posted: 05/15/2008 17:32 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
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Sorry, i meant a single pneumatic valve.
And BTW, i'm trying to use as little amount of valves as possible, thus achieved by hooking up all rockets to one valve.
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| STHORNE |
| Posted: 05/15/2008 17:34 PM Post subject: |
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Master of Spuds
Joined: 14 Feb 2007
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hmm...I have an excellent plan. Let me draw it up for you.
should only take a sec 
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| DYI |
| Posted: 05/15/2008 17:38 PM Post subject: |
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Rear Brigadier
Joined: 07 Jul 2007
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Uh... what kind of pneumatic valve? There are tens or possibly hundreds of different types.
The Mythbusters built a water bottle "jetpack", and it needed 50 bottles, if I remember correctly. Each one provides a rather miniscule amount of thrust and, as I said, the power:weight ratio is too low. It doesn't matter how many you attach, the power:weight ratio of the rocket itself will never change. This means that you need to attach a ridiculously sized bank of rockets to a very small and light vehicle, and you will obviously never be able to go any farther or faster than a single rocket on a tether.
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| igpay |
| Posted: 05/15/2008 17:42 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
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Wow, sorry you guys, i'm really being vague today.
I was thinking modified sprinkler valve, and even though the power:weight ratio will never change, wont the car keep getting faster if you strap more bottles onto it? (until like you said, it reaches the speed of "a rocket on a tether")
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| Acdcmonkey1991 |
| Posted: 05/15/2008 17:43 PM Post subject: |
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Donating Member
Joined: 30 Mar 2007
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I did a test with a water rocket about 2 months ago. It was about 6 feet of 2 in. PVC normal temperature at 90 psi. The valve a used was a simple 1/2 in. ball valve but my friend would hit it with a hammer. He wieghs about 110 lbs and when we strapped this to a dolly cart, he went a good 6 ft., I know it doesn't sound like much but it was hell-cool. I think I already posted some plans to one here. I figured out that a much more efficent system would be to have a piece of 3 ft. pvc pipe with a piston inside and a burst disk at the end. when the main valve was releasedon the air tank, the air push the piston forward super compressing the water and popping the burst disk, shooting out a jet of water.
Heres my thread, I believe Ragnorak suggested the piston idea.
Posted are my new plans too (rough sketch)
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Last edited by Acdcmonkey1991 on 05/15/2008 18:13 PM; edited 1 time in total |
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| igpay |
| Posted: 05/15/2008 17:48 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
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So if 6 feet of 2 inch pvc (which has about the same volume as maybe 2 bottles or less) can get you 6 feet, 10 bottles at 100 psi could get you a little over 30 feet ! 
@+, I'm a good amount lighter than your friend, and i plan on making something less heavy than a dolly cart.
EDIT: and yes i believe you can use high pressure water w/ sprinkler valves.
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| STHORNE |
| Posted: 05/15/2008 17:53 PM Post subject: |
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Master of Spuds
Joined: 14 Feb 2007
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Here, before examining my plan, look at this gun to see what I mean by them:
Trident Antenna Launcher
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The blue arrows indicate the air flow to the bottles
The green is the modified sprinkler valve |
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| igpay |
| Posted: 05/15/2008 17:53 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
Posts: 88
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Actually, 6 feet of 2 inch pie has less volume than a 2 liter bottle!!!
were talking distances of 50+ feet here!!!
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| igpay |
| Posted: 05/15/2008 17:55 PM Post subject: |
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Sergeant
Joined: 08 Apr 2008
Posts: 88
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sthorne,
thats what i was originally thinking. And don't you mean air flow from the bottles?
EDIT:Oh, sorry.
Last edited by igpay on 05/15/2008 18:03 PM; edited 1 time in total |
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| STHORNE |
| Posted: 05/15/2008 18:00 PM Post subject: |
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Master of Spuds
Joined: 14 Feb 2007
Posts: 1170
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| igpay wrote: | sthorne,
thats what i was originally thinking. And don't you mean air flow from the bottles? |
yeah, to and from. Same difference, you know what I mean
and please refrain from double posting. just use the "edit" tool.
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