Spring RTS Engine

So i decided upon building a spudgun after having had the thought in my head for months.

I began searching the internets for tips, instructions and what not. A week ago i decided i knew enough to make a simple combustion-style one, so i bought some PVC pipe and fittings.

(Pic will go here once i gets the camera back)
I read that a fan in the chamber would increase the performance about 25-30%, so i found a 90mm brushless computer fan which i appropriated for my needs using a dremel

After that, I started thinking about ignition. There are many ways to do this, ranging from poking a match or a lighter through a hole in the chamber (If you do this you deserve it) to using multiple flyback transformers to create sparks everywhere in the chamber.

I settled after some thinking for a BBQ igniter (pushbutton piezo thingeh). As a side note, no general stores seem to carry disposable cameras any more :/

After searching stores around where i live and the internet for a few days, i just looted one from my our propane grill (We never used it anyway meh)

Now for somewhere to create the spark inside the chamber. I made a ghetto spark strip out of two washers and a penny for this purpose.

(pic goes here when i gets the camera back)

With both the fan and the ignition done, I started on joining my parts together. Most spudders use PVC cement for their assembly, but seeing as no plumbing-supply stores seem to carry that either, i used plastic cement and screws instead (and i really hope this holds)

After letting hte cement dry overnight I started drilling holes for screws and putting the fan and ignition in there.

Now it was time for putting the whole thing together

After an anxious nights waiting while the cement set, I was finally able to try it out.

I stuffed a plug of newspaper into the barrel (just to hold the gases in the chamber), sprayed some deodorant in there and closed 'er up.
Now to stand back a bit, push the button and watch the boomshine.

Click... Click.. Clickclickclickclick

It appears that the spark strip for some reason shorted out and didn't give me a spark .(


As i couldn't get it out (it was wedged in by the fan), I had to make a new one which was thinner and poke it in there.

A two minute hackjob which produced a single, but consistent spark.

After installing my new spark gap, i primed 'er up again.

This time however, the click was instantly followed by a loud bang which left my ears ringing. I cackled like a maniac; MY GUN WORKS!


(the poor newspaper plug got it the bad way .( )

After firing a few more blanks with newspaper plugs, I went inside and got me a tater. I loaded it and primed up the gun.

Stepping back, i pushed the button.
BANG. The recoil rocked the mount and knocked all the stuff off it.

It appeared that the mount wasnt the only thing that got knocked off.



I knocked a board clean out of the wall, taking the eight nails with it and vaporising the poor 'tato in the process


(these were the only parts of the valiant potato i could find, apart from a thin white film of starch)

Im going to field test it tomorrow if the weather and all permits. Hopefully i will have an estimate of muzzle velocity, energy and range by then.

Reminds me of when i used to fire model rockets from a makeshift shoulder launcher using old uttering and a piece of perspex as a shield.. ^^

make a video of it firing!

Nice

1. You're one of my heroes.
2. I'm making an electric motorcycle. Should I mount a weapon?

YES

neddiedrow wrote: 2. I'm making an electric motorcycle. Should I mount a weapon?

The answer should be given .D
Make a small ~1m spudgun and mount that, would be awesome

EDIT: Future plans for this is cleaning up of the exterior wiring (its very messy atm), clicky button for the fan and a laser sight :3
Dealextreme sells that kinda stuff dirt cheap, thanks for spamming linky caydr <3

neddiedrow wrote:2. I'm making an electric motorcycle. Should I mount a weapon?

Are you insane? Why do you even have to ask that?

FUX YES!@

I'm very curious about the range :D

espylaub wrote:I'm very curious about the range :D

As am i, i didnt get the opportunity to bring it out and measure it up today
Tomorrow hopefully..

Parts for a laser sight ordered, eta 14 days...

neddiedrow wrote:1. You're one of my heroes.
2. I'm making an electric motorcycle. Should I mount a weapon?

?

oh man, man oh man oh man...

spud gun = northerner hackjob at what we invented in the south...

its called a POTATO CANNON!

and you build it with 3" steel pipe! weld it together, and epoxy a coke can on the front to slice the potato to the EXACT diameter of the cannon, put a screw-off cap on the combustion chamber on the back, and 2 small holes for the ignition.. what the crap was with the fan and whatnot?? oh man, you are making it too complicated, and not dangerous enough...

anyways, loading and firing is easy, load it like a musket, stuff the potato down the open end, let the aluminum can shear the potato to a perfect firing shell, and use a stick/plundger, whatever as a ramrod to get it flush to the ignition chamber. then, flip the cannon over, open the back of it, spray in about half a can of hairspray, and have the ignition on the side of it...

screw the cap back on, point and click

it'll put a hole in a brick wall as long as it dosen't explode...

wadding, newspaper and a die sized potato spitwad..

you make me giggle.

I was thinking something a little more practical and a little less phallic.

LathanStanley wrote:oh man, man oh man oh man...

spud gun = northerner hackjob at what we invented in the south...

its called a POTATO CANNON!

and you build it with 3" steel pipe! weld it together, and epoxy a coke can on the front to slice the potato to the EXACT diameter of the cannon, put a screw-off cap on the combustion chamber on the back, and 2 small holes for the ignition.. what the crap was with the fan and whatnot?? oh man, you are making it too complicated, and not dangerous enough...

anyways, loading and firing is easy, load it like a musket, stuff the potato down the open end, let the aluminum can shear the potato to a perfect firing shell, and use a stick/plundger, whatever as a ramrod to get it flush to the ignition chamber. then, flip the cannon over, open the back of it, spray in about half a can of hairspray, and have the ignition on the side of it...

screw the cap back on, point and click

it'll put a hole in a brick wall as long as it dosen't explode...

wadding, newspaper and a die sized potato spitwad..

you make me giggle.

You'll never put a potato or anything for that matter through a brick wall with that fyi
On the fan, i shall direct you to Burnt Latke
And a spreadsheet for tl;dr

And if you're going steel anyway, why not make it a hybrid? you could go 4x MAPP if you have decent fittings (and some cover just in case)

EDIT: spudgun is the general term for it: http://en.wikipedia.org/wiki/Potato_cannon

Personally i call it potatiskanon, which directly translated is potato cannon

├âÔÇ╣DIT2: A steel pipe for a simple combustion is probably as safe as you get

neddiedrow wrote:I was thinking something a little more practical and a little less phallic.

But it's a Vespa!

"spud gun" is called so because it removes many unnecessary syllables. I really doubt it has anything to do with northern slang... I've always called them potato cannons.

may i suggest to use a stronger fuel?

if you feel confortable about the combustion chamber strenght, i'd suggest a cheap hydrogen peroxide (in high concentrations like > 50% would be nice, but i guess that commercial 16% would to as well) & etilic alcohol as binary self-oxydating fuel

using 70% peroxide, the mixture will burn around 1000 kelvin wich explodes into a supersonic shocwaves 'cause of the instant water phase transition
(the high temp is actually above the water critical temp)

C2H6O + H2O2 was actually the V2 second stage fuel compund, the one wich allowed supersonic speeds

another alternative might be low pressure hydrogen & oxigen mixture generated on-place by water electrolysis

Brain Damage wrote:may i suggest to use a stronger fuel?

if you feel confortable about the combustion chamber strenght, i'd suggest a cheap hydrogen peroxide (in high concentrations like > 50% would be nice, but i guess that commercial 16% would to as well) & etilic alcohol as binary self-oxydating fuel

using 70% peroxide, the mixture will burn around 1000 kelvin wich explodes into a supersonic shocwaves 'cause of the instant water phase transition
(the high temp is actually above the water critical temp)

C2H6O + H2O2 was actually the V2 second stage fuel compund, the one wich allowed supersonic speeds

another alternative might be low pressure hydrogen & oxigen mixture generated on-place by water electrolysis

Im not suicidal mate, self-oxidating fuels are really powerful
Remember, my gun is made of PVC .)

Although i'd love to make a steel gun to try such fuels out

The Peroxide stuff looks like deflagration to detonation transition to me, and that's been known to bust 1cm wall steel pipe. Not with those fuels though

Also, if we're on that track anyway... Pressurized Acetylene + pure oxygen

Comp1337 wrote:Also, if we're on that track anyway... Pressurized Acetylene + pure oxygen

Did an oxy-acetylene bomb in college. Five story fireball. State police. Not pretty.

Erom wrote:

Comp1337 wrote:Also, if we're on that track anyway... Pressurized Acetylene + pure oxygen

Did an oxy-acetylene bomb in college. Five story fireball. State police. Not pretty.

Oh man, you should gotten pics of the boomshine

But anyways, yeah oxy-acetylene is way too dangerous to use in a potato gun if you value your various body parts

How about hydrogen? Easily obtainable through hydrolysis.