SpudFiles

$1: El Cheapo grill lighter
$2: Epoxy (not fast drying!)
$3: 5 gallon water jug
$4: 4 foot length of 1.5" ID Schd-40 PVC
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$10 + tax

My first large chamber improvised combustion cannon, as I had crushed (by accident) my first combustion cannon which was made from a 2-liter bottle & 2 feet of 1.5 inch Schd-40 PVC.

On a side note, when trying to make a spud gun safer by inserting the 2-liter bottle end into a large diameter cardboard shipping tube (super thick btw) & filling it with foam for stability, don't use triple expanding foam. It will crush the 2-liter bottle. Use the minimal expansion stuff for sealing around window frames. Much less crushing.

I built this by heating & widening the lip of the water jug to accept (very tight fit) the PVC barrel, & widening the lip a bit to give room for the epoxy. I then mixed the 1 hour epoxy (don't use fast set epoxy, it doesn't set into a hard resin, it crystallizes on the molecular level, providing a brittle bond).

With the epoxy resin mixed, I slathered it generously on the end of the barrel to be inserted into the jug after roughing it up with 80 grit sandpaper (better bond).

I inserted the barrel, most of it got squeegeed back out, but slowly crept back in. I then slathered more on the lip of the jug & onto the PVC to make a thicker ring like bond.

Once done I measured my grill lighter, drilled a pilot hole 3/4 of the diameter of the grill lighter's business end into the end of the water jug, as you can see in the pic & proceeded to heat the area up with said grill lighter.



Once it was hot enough to work with I inserted the gril lighter & twisted it around enough while it was cooling to provide just the right size entry hole for the lighter without being a mega tight squeeze on entry.

Loaded a prescription pill bottle in it (filled with sand), bottom first, cap pointing towards the open end of the barrel. (The prescription bottles I get are just the right diameter around the cap to provide a smooth sliding fit down this barrel)

I gave it a 2 second burst of propace from my torch tank, inserted my lighter... How's that song go?

Click. Click. BOOM!

I lost sight of the pill bottle (yes, I was smart enough to remove the label)
& realized it was waaaaaay louder than I thought it would be & proceeded to run inside my house as my neighbors laughed at how surprised I looked.

Here's the pic:



P.S. Don't be alarmed if this thing temporarily expands when you fire it. It does due to the indents in the walls & bottom. Also it is mega cool to fire at night, although the combustion is visible in daylight, at night it lights up everything around it, including you in a sppoky flashlight under the chin fashion.

The reason I chose this chamber was because one, it was cheap, two it was large & three because of the seams. Having seen chambers burst into jagged edges &/or shards, this is safer in case of an oops-overfuel. It is more likely to expand & crack at the seams causing a terrible scare, maybe a hot flash, few burnt hairs, but likely no shrapnel in your body.

Watch yourself mate, one of those bottles blew up catastrophically (with shards) when used as a combustion gun such as yours.

Really? I thought it wouldn't due tot he flexible plastic sides/bottom & the seam.

Maybe I will house this one then. I can get over sized cardboard tubes (I mean LARGE + thick walled) & put it around this, cap the ends & make sure I have a port for the barrel & the lighter.

How did this particular bottle type explode & how badly were they injured?

TBH I was worried that I may pop it due to the design & the thin walls, but I thought it wouldn't happen if I was careful with the gas.

Yea, even if you're still going to shoot this then ear protection would be a good idea. If that failed catastrophically your ears wouldn't appreciate it.

I had a combustion like this, which was much smaller (polypropylene iirc?) I had something too tight in the barrel and it fired, but ripped itself to shreds. Because it was so small, I wasn't injured, but it could have been far worse. The next day my hearing was crap, and my ear rang for over a week!
Check the plastic type of this bottle, and see if you can find details of anyone who has pressure tested one (I'm sure I've seen them used for water rockets)

The bigfoot guy and the guy with the hydrogen launcher used one to launch pumpkins.

I'm going to take a guess that they were remotely fired. They were also wrapped in fiber tape and reinforced.

Would I stand near one? Hell no.

I think I will reinforce it with strapping tape & reinforce it with an epoxy resin after adding the tape. Give it some real staying power.

The bloke got a few cut nothing major but he was lucky.

Pretty cool!
I like your writing style too jaythedog.
I had mentioned an idea with one of these jugs I have in an ITWOST.
My idea involved 10 feet of 1" pvc, the 5gal jug, and putting a 1" "T" (for venting and filling (through a ball valve, and barrel removal) with JB weld and about 4 hose clamps around the opening.
Been thinking of doing a pneumatic one similar with a 1" sprinkler valve.
That way I could hydrotest one first.
It would be cool to shoulder fire with the tank out behind and the long barrel on shoulder (at a safe pressure).
Noticed lately the same diameter jugs only shorter and half the volume, 2.5 gallon!!!
BTW, I have the parts needed so I was thinking of shooting some long giant arrows from one (seems better suited/more efficient because of the large volume, long barrel, but low pressure) but no time for it if I can't shoulder fire it safely. Nice post! 8)

Thanks TL, just remember to be safe is all. I like the suggestions above, maybe heavily coat it in fibrous strapping tape & give it an epoxy coating. This should bring the pressure rating up. I will do some tests in the next week or two & post my findings after I pressure test it at 250psi.

Keep in touch!

P.S. By heavily coat I mean I am going to make this thing have 1" walls lol.

I have a tank vat I can fill full of an epoxy resin (I have industrial stuff available in large amounts) so I can dip it, let it dry, repeat as necessary.

TTYS!

...1" walls...

Geez, I'd be too worried they'd turn into 1" shrapnel!
And 250 psi? that seems way too high for this,
I was imagining pressurizing to about 30-40 or maybe 50psi operating pressure (if I determined that safe), with that volume, and a long barrel, and using longer heavy projectiles, it would still be impressive IMO.
For moar pressure, I'd just go with a better factory rated tank.
(a Cheap compressor tank at it's rating etc.) For higher press., safety, spend another 10$.

BTW, I was reading about the battle of Fredericksburg where a cast cannon exploded the 30th or 50th time it fired, and a piece of shrapnel almost hit R.E. Lee! That was quite common for them to explode (hugely) after being fired that many times. Makes me wonder if the powder wasn't bad(?) or they developed unvisible cracks first(?). 8)

jaythedogg wrote:I have a tank vat I can fill full of an epoxy resin (I have industrial stuff available in large amounts) so I can dip it, let it dry, repeat as necessary.

TTYS!

Dont tell JSR or you may find it missing one day...

Dang, Carlman, both our replies went through at the same minute.
True, A Vat of industrial epoxy?:lol:
The prankster possibilities too! 8)

EDIT: now I'm daydreaming up a large volume, lower pressure pump, as opposed to a smaller volume higher pressure pump.
Dang, no time for that right now. 8)

Double, but I was doing yard work, and thinking it would take me about half an hour to throw a pneumatic together using 10ft. 1" pipe and my 5 gallon tank, and an old 1" sprinkler valve,
decided to check how much overkill the chamber would be,
filled the entire ten foot 1" sch 40 with about 1.5 liters!!! (should've used a math formula earlier).
(There's around 18.9 liters in 5 gallons) (over 120ft. of 1" would give a good 1:1 ratio!!!) With a two liter, that would give almost exactly a 1.25:1 C:B ratio, still overkill a little!
Maybe the 2.5 gallon version of those into a larger pipe and using a sabot or wadding would be OK.
Still the 5 gallon combustion seems cool... except remote firing. 8)

I think a 1" wall of epoxy might be overkill, but if its for the sake of safety. more power to you.

Perhaps if you wrap the chamber with a layer of strong fabric in between layers of epoxy it would be a lot harder to explode violently.