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Dynajet spudgun?

A place to ask general spud cannon related questions.
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should this be attempted?

yes!
6
60%
hmmm the theory is good but some things should be added/changed
2
20%
i have no clue what you mean!
2
20%
 
Total votes : 10
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Dynajet spudgun?

Unread postAuthor: thespeedycicada » Mon Nov 12, 2007 5:03 pm

My side hobby from spudding is pulse jets and i have to say they are amazing machines but i wont be able to run mine for quite sometime because of my current location so why not combine my two wonderful hobbies? The principle im running off here is the valved pulsejet like the argus flying bomb or the dynajet these are not like the valveless type jets! valved jets are much different.How a dynajet (or any valved jet) works is when the fuel combusts in the chamber as it accelerates out creates a partial vaccum in the chamber situated in the front of the jet is a reed valve the vaccum pulls this valve open sucking in fresh air and if its running off a liquid fuel it pulls that in aswell.So why not use this on a spudgun? you situate a magazine at the front of the "gunjet" and supply it with a constant ignition (this is not necessary if you want semi auto) and gas (propane,mapp,etc) the gun fires expelling the projectile and opening the reed refreshing the air while the mag loads a new projectile in the barrel.Then the combustible gas goes into the cc and is ignited and the process repeats itself.The theory should be good but is it worth trying? the auto combustion that could result would be a big leap in spudding no?

PS.this gun will not glow red or get very hot at all the pic is what it would look like in pulse jet mode only. Thank you.
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lbc_dynajet_heating_ss_crop1_516.jpg
dynajet running.
lbc_dynajet_heating_ss_crop1_516.jpg (35.74 KiB) Viewed 1088 times
Last edited by thespeedycicada on Mon Nov 12, 2007 8:17 pm, edited 1 time in total.
current projects: co-axial piston valve.Status DONE!
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Unread postAuthor: benstern » Mon Nov 12, 2007 5:14 pm

Seems way too unsafe as far as heat for spudgunning.
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Unread postAuthor: hi » Mon Nov 12, 2007 5:19 pm

ive always wanted to build one of those...

i actually thought of this not to long ago, but like benstern said, i think its a bit hot for potatoes...

maybe you make a full auto golf ball gun...
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Unread postAuthor: thespeedycicada » Mon Nov 12, 2007 5:30 pm

The gun wouldnt get nearly that hot the frequncy these machines run at is EXTREMLY high if the gun shot that fast even if the mag held 300 golf balls it would be emptied in like 1 second or lower.The gun will not get that hot as it will most likely be semi auto anyway.[youtube]http://youtube.com/watch?v=G7rZWBJ7ZLY[/youtube]
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current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
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Unread postAuthor: Zen/// » Mon Nov 12, 2007 5:41 pm

The vid brings up ideas for other uses like a quick way to bond metals together.

For spudgunning it would overheat and maybe make the golfballs catch on fire.
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Unread postAuthor: thespeedycicada » Mon Nov 12, 2007 6:00 pm

But it will not over heat the mag would on hold about ten golfballs and even if i fired it on auto it would not catch the golf balls on fire. the reason pj's heat up is because of the very high frequency they run at. over heating will not be a problem as you would not use pvc unless it was semi auto but pvc would still be bad i really do not see why everyone thinks it will over heat it will not come close to these temps!! it is just a semi auto or auto gun that runs off the principle of the valved pj and will not run like one it would be just like a normal spud gun but with semi auto capabilities! so please dismiss the thoughts about the gun turning red hot as it will not do so unless it is ran like a pj.
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current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
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Unread postAuthor: potatoflinger » Mon Nov 12, 2007 6:44 pm

Well, it seems like it would work, but the hardest part of making a semi our full auto gun is the loading system.
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Unread postAuthor: Hubb » Mon Nov 12, 2007 6:48 pm

Reading the posts, I would assume a reed valve is very similar to a check valve?

Anyway, that's a very interesting way to combine one's hobbies. And fire is always cool :twisted: .

Good luck and God Speed (pun untended).
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Unread postAuthor: Hotwired » Mon Nov 12, 2007 7:35 pm

So, a incredibly high ROF of roast potatos :P

I'd be seriously worried about a cannon next to me that glows white with heat in use.
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Unread postAuthor: Fnord » Mon Nov 12, 2007 7:54 pm

From what I've gathered, pjs are kind of touchy when it comes to flow restrictions, so I don't know if this would work. It may not be a big problem for semi-auto mode, but any full auto action would probably take some tinkering.
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Unread postAuthor: thespeedycicada » Mon Nov 12, 2007 8:14 pm

I see what you mean fnord valved pjs are a huge amount less sensitive to things blocking the exaust than valveless due to the valve i dont hink full auto would be easy but semi auto might not be hard.i will say this once more so i wont need to say it again this gun will not glow red pjs glow red because of the frequency this gun will not come near that and may not even be full auto so please stop saying that it is a bad idea because it will light the ammo on fire or something!!!! Really sorry if anyone gets pissed its not meant to be rude/mean just want to let everyone know to stop saying it will glow red it just wont glow it will get to hot to hold in full auto if get it to do that but it wont glow.
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current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
NEXT project:auto piston valve.
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Unread postAuthor: Novacastrian » Mon Nov 12, 2007 8:27 pm

Thats cool, have you used your jets in any planes yet, how much thrust is that one you linked producing?

I think that the use of a pj in a spud gun would be insane (in a good way).
Good luck Speedy- if you decide to go ahead let us know :wink:
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Unread postAuthor: thespeedycicada » Mon Nov 12, 2007 9:51 pm

No i have not used my jets in planes and probaly never will as these planes can reach 200+ mph! Besides my jets are valveless like the one below.The dynajet produces around 4 lbs of thrust and is about 1 lb or less in weight.I most likely will start this project tommorow but morre comments/suggestions will be appreciated the prototype will be pvc to test the theory.I also encourage some of you guys to get into pulse jetting its reallly addicting seeing a heavy tube get red hot in 15 seconds with enough noise to blow your eardrums.Ahhh the two of the most dangerous hobbies ever,spudding and pulsejetting.
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lockwood valveless pj.
current projects: co-axial piston valve.Status DONE!
S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
NEXT project:auto piston valve.
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Unread postAuthor: Tom » Fri Nov 30, 2007 4:29 pm

My friend made a jet engine kart from a turbo last year, it went very fast.
I never liked pulse jets because they are having to much complicated parts, except the valveles one but that isn't really handy on a go-kart :D .
GR.Tom
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Unread postAuthor: BigGrib » Fri Nov 30, 2007 5:06 pm

on the contrart i have seen valvless pulsejets on a go kart before and it was insanly fast. crazy
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