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| Joseph Kaile |
 Posted: 07/14/2005 13:50 PM Post subject: Rocketboard: Rocket-Propelled Skateboard |
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Private
Joined: 14 Jul 2005
Posts: 1
17.98 Spud Bux
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The Rocket is made of a 3 inch PVC pipe capped at both ends. The pipe is filled with 6 pounds of a Potassium Nitrate/Sugar mixture. Potassium Nitrate, also known as saltpeter can be obtained at any gardening center or pharmacy. This wire leads to an igniter planted in the core of the rocket. When I attach the alligator clips to the 6 volt battery, it completes the circuit sending electricity through the wires. A nickel chromium wire is banded at the tip and begins to glow red. This ignites the pyrotechnic material which consists of a high temperature nitrocellulose/black powder pyrogen. Nickel chromium is the same wire used in toaster ovens. When the propellant burns, the reaction yields a white smoke which expels through the nozzle. This 1/4th inch nozzle concentrates the smoke making the rocket propulsion more powerful causing the propellant to burn faster under a higher pressure. The Newtonian law is then applied: “to every action there is an equal and opposite reaction.” The rocket expels a powerful force outward, thrusting the skateboard the forward.
http://www.putfile.com/media.php?n=rocketskateboard |
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| spudshot |
| Posted: 07/14/2005 14:07 PM Post subject: |
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Brigadier General
Joined: 03 Oct 2004
Posts: 1044
41304.56 Spud Bux
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| cool, but i dont know if this is allowed here, i might need to delete the topic if PC says its not allowed, post it on BC's site and saladtosser's site, they dont give a flying fork about people posting explosives |
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| drac |
| Posted: 07/14/2005 14:46 PM Post subject: |
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Metalhead Moderator
Joined: 24 Apr 2005
Posts: 894
5173.40 Spud Bux
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| iamthewalrus |
| Posted: 07/14/2005 15:01 PM Post subject: |
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Colonel
Joined: 28 Feb 2005
Posts: 560
11.92 Spud Bux
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| let me cut dracs post into the three words for u: NI, CE, !!!. I also agree with drac, but i can say it in one word, NICE!!! |
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| drac |
| Posted: 07/14/2005 15:06 PM Post subject: |
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Metalhead Moderator
Joined: 24 Apr 2005
Posts: 894
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| Umm, if you didnt notice, Walrus, there are three words in my post. I told BC this was a real brain buster. lol |
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| boilingleadbath |
| Posted: 07/14/2005 16:07 PM Post subject: |
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Joined: 12 Mar 2005
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| Next time, they should use somthing with a bit more heat resistance for the nozzle - enlargeing it that much during use will significantly reduce the specific impulse and thrust... they should try a iorn endcap. |
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| PCGUY |
| Posted: 07/14/2005 17:01 PM Post subject: |
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Joined: 18 Aug 2004
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It's OK to post this here.
I happen to mass produce smoke nades for people, using the same mix but in about 14" of 3/4" SCH80. I suggest trying to get some thicker pipe, or start using steel becuse as soon as the side pops open, your losing a lot of power. With my SCH80 the side pops open becuase it burns for over 2min, but 2min is a long time for a smoke bomb.
Also it's easy to make it pop open, once my outlet hole was too small and I shot the cap straight off. It had to travel at LEAST 3 blocks, however we coulden't find the cap  |
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| Darkerweb12 |
| Posted: 08/22/2005 23:37 PM Post subject: |
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Joined: 20 Aug 2005
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| I do not believe that a saltpetre and sugar mixture can obtain the high velocity burn of a saltpetre/charcoal/sulfer mixture can. If im correct, your rocket will only emit fast smoke not thrust. Although, an outlet nozzle that is too small to correctly vector thrust can and will build up pressure, dangerously exploding the nozzle, or quite possibly the entire mixture. Now if that was under or on the sides of a skateboard with YOU ON IT, that would not be entertaining, I would rather not build this then have my foot/leg/lower torso blown off by bad construction methods.... I reccomend taping bottle rockets without the stick onto finger skateboards! |
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| spudshot |
| Posted: 08/23/2005 5:48 AM Post subject: |
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| Darkerweb12 wrote: | | I do not believe that a saltpetre and sugar mixture can obtain the high velocity burn of a saltpetre/charcoal/sulfer mixture can. |
what? that mix is gunpowder! i wouldnt try that |
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| PCGUY |
| Posted: 08/23/2005 5:56 AM Post subject: |
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| boilingleadbath |
| Posted: 08/23/2005 16:56 PM Post subject: |
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"fast smoke"
Ok, wise guy, I hope you where being sarcastic. Fast smoke is the friken' cause of thrust in a rocket. (3|-|, |\|3\/\/70|\|?)
ISP, or specific impulse, is the measure of how fast the smoke is going. |
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| Darkerweb12 |
| Posted: 08/24/2005 19:53 PM Post subject: |
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Joined: 20 Aug 2005
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ok, wise guy, smoke is not thrust, smoke is unburnt chemicals in the reaction, most commonly carbon. thrust is hot gases expanding, causeing a equal and opposite reaction, which is used as thrust. PCGUY, i suppose if the smoke 's powder is loose enough, it would be more rocket than smoke , but also produce smoke. I thought you were talking about a slow, large volume of smoke being created, like most homemade/commercial smoke ....I stand corrected...
spudshot, that mix i described is the common smoke bomb mix, not gunpowder. i belive gunpowder is 75% potassium nitrate, 10% Charcoal, and 5% sulfur, but i could be wrong. |
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| boilingleadbath |
| Posted: 08/24/2005 21:03 PM Post subject: |
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Saying smoke doesn't cause thrust is like saying that the propeller doesn't make a boat move... it's really the spinning of the propeller that does it.
Likewise, it's the fact that the propelent gass (typicaly with smokey particulate in it, as we don't have the privlige of using high-purity liquid fuels) is thrown out the end of the craft, not what it is... it can be H2O, CO2, any mixture of the before-mentioned, xeon, fusion produced helium plasma, noxious combustion products, or frog guts... if moves backwards, it'll work.
Now, you can say that a slow buring propelent grain won't preform well, and I'll agree in a way; you won't get much thrust. (because your mass flow is low) However, using a properly sizes nozzle, your specific impulse - exaust velocity - will be nearly as good as if you had a higher mass flow. The solution is not, however to pack your pipe full of peppercorn sized bits of self-oxidizing flamables. There are significantly safer ways of increasing surface area. (in fact, rockets that are dropped (the big ones, anyway) are not used - the propelent grain may have cracked. This causes an unpredictable burn, and is likely to make it go boom.) |
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| corkie |
| Posted: 09/21/2005 13:08 PM Post subject: |
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Joined: 21 Sep 2005
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love the idea but seems a bit dodgy.  . but hey ho good idea all the same!  |
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| toza |
| Posted: 01/16/2006 21:46 PM Post subject: |
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Specialist
Joined: 05 Oct 2005
Posts: 50
86.88 Spud Bux
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| yeah i gree i wouldn't be getting on that skateboard anytime soon but a great idea all the same. do you think it would work with a bike? or would the bike be too heavy? the mixture and stuff just needs a bit of fine tuning but once you get it safe and easy to use its gonna go global!!!! |
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