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The DYI GO-kart Project: Rocket design

All non-spudgun related discussion goes here such as projects, theories, serious questions, etc. All "off-topic" posts (aka useless posting, determined by moderators) will be removed.
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Unread postAuthor: ammosmoke » Thu May 15, 2008 11:13 pm

But ermm, wouldn't the water flash to steam when valve is opened? I know water can't boil under pressure, hence the flash to steam. So why couldn't my idea work as long as the temp got up to 300 celcius?
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<img>http://www.speedtest.net/result/309559995.png</img>
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Unread postAuthor: Lentamentalisk » Thu May 15, 2008 11:45 pm

What was your idea? to shoot it? that is a realllllly bad idea if that is what you are referring to. Triggered burst disks are fairly easy to do. As to lightening the tank, I would suggest that you look into how paint ball HPA tanks do it, and try to emulate that. And of course, no corners what so ever!
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Unread postAuthor: ammosmoke » Fri May 16, 2008 12:08 am

Well, not really shoot it. I was being sarcastic, but that wasn't very clear. Sorry...
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Unread postAuthor: daxspudder » Fri May 16, 2008 1:50 am

I think this is a great idea, but i think using 4500 psi is better for the amount of weight you want to move, it will get off the line quickly, and continue to accelerate a good little bit, this is a great idea. also, designing and implementing a air eductor on the outlet will greatly increase thrust, if your not familiar with an eductor, it uses a pressure source passing through a venturi point to increase speed, with an opening ... bleh ill make a picture...
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Attachments
eductor.JPG
crude, but it shows how the expanding water will pull air in( it will create a vacuum) and greatly increase thrust
eductor.JPG (11.53 KiB) Viewed 335 times
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Unread postAuthor: jimmy101 » Fri May 16, 2008 10:53 am

How are you going to keep this thing on the ground and tracking straight? I would think that is the most important, and difficult, challenge. There are many kinds of engines that'll get the performance you want but if you can't keep the thing tracking straight it'll crash long before you get up to a decent speed.
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Unread postAuthor: rcman50166 » Fri May 16, 2008 11:13 am

Ok I'm gonna try to find an earlier post I made on the water rocket. But until then, The rocket you are going to need to use will have to be determined by your budget. Water rocket is by far the most powerful type of rocket as far as impulse goes (N/s) but it's also potentially the most expensive. The tank on one of those rockets are very dangerous if not properly made and tested. The same goes with the valves. They are designed and built for high temp. and pressure. Get past that and there will be plenty of thrust. There would be no real need for and eductor. 150km/h isn't very much however. I would just use solid fuel rockets or hybrid fuel. Hybrid provides throttling and inert fuels which could be beneficial. A Wiley Cyote solution but it's plain and simple. Just remember to use tires and brakes rated for those speeds.

rcman50166 wrote:Uhh.. I hope you have a lot of money. I've looked into those things. The valves used on those are custom made. They are typically spring assisted butterfly valves designed to hold the temperature and pressure created by one of those monsters. There is a main valve that propels it and there is a initiating valve that starts the flash boil reaction. I've seen water rocket dragsters that use over 10,000 PSIG @ 900 degrees fareinheit. Dangerous stuff. Be careful.
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Unread postAuthor: BigGrib » Fri May 16, 2008 8:18 pm

Ok so you're asking how to lighten the thing as a whole correct? Well, what are you making your pressure vessel out of?? I thought I saw you said concrete up above. why not just use a high pressure cylinder for your vessel. remove the stock valve and put a ball valve or something into it. heck i dont know that just ran through my head.
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Yea, that's definitely going to get you at least a tazer.

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