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Spud gun powered by cooking oil?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Spud gun powered by cooking oil?

Unread postAuthor: Doctore » Sat Nov 16, 2019 1:31 pm

Hello everyone!

I would like to share with you this rather crazy combustion cannon design. I am fairly convinced that it could work, but there is always a chance that the design might be flawed. As always, I am looking forward to your opinions and ideas.

To better understand how this cannon is supposed to operate, think of it as composed of 3 sections.

The first section is the compressed air storage vessel pressurized to at least 150 PSI. Ball valve would separate it from the second section, which is the fuel compartment. This section would be of tiny volume and only a few drops of fuel would be needed.The ideal choice would be ethanol or gasoline. Fuel compartment would be separated from the third section, which is the main firing chamber, by a tiny rubber plug. This plug would be necessary to separate fuel from heat and oxidizer as you will see later. The main firing chamber would be of bigger volume and two systems would be embedded in it - ignition system and an air feed system. There would be no separation between this chamber and the barrel.

Ignition system would be composed of at least 6 modified car cigarette lighters, depending on the volume of the main firing chamber. Enough direct current would be provided to them as all of them would have to glow red hot prior to firing.

Air feed system would be composed of two electrical air pumps that would feed air into the main firing chamber. Two one-way valves would be placed. These pumps would operate constantly to create positive pressure in the main firing chamber of at least 50 PSI. Now, it is important to note that the projectile would have to be designed in such a way as to not create a complete seal, and to leak air at a specific rate. Leak mustn't be great as to allow pumps to easily maintain this pressure. This Projectile also mustn't move or leave the barrel while constantly exposed to 50 PSI.

You can see components in this paint image.

Image

Firing sequence!!

The first task is to place your specially designed projectile in the barrel. Then you place the fuel in the fuel compartment (few drops, ethanol - gasoline). This section would be designed to be detachable for ease of placing fuel. Then the storage vessel with the ball valve is pressurized to at least 150 PSI. Next, air pumps are switched on and you wait until the constant pressure of at least 50 PSI is achieved. Finally, the ignition system is switched on. I guess it would take an additional 10 seconds until all lighters are glowing red hot.

All you need to do now to fire it is to pull the ball valve - pressurized air rushes into the fuel compartment, mixes with fuel to create vapor, rubber plug is pushed out by this vapor-air mixture which now makes contact with these modified cigarette lighters and reaction commences. Yes, I know that rubber plug could mess up these lighters, but it is the only solution I can think of right now. Air pumps connected to the main chamber are simply to provide additional oxidizer.

You are probably wondering where is the cooking oil part! Well, if this turns out to work properly, perhaps you could use diesel or cooking oil as fuel. I am aware that both of these fuels do not burn cleanly and could mess up this rather expensive and difficult to install ignition system. Gasoline also has nasty substances in it so ethanol would be the prime choice. As for the cooking oil, I guess you need more lighters and more chamber volume.

I also contemplated a semi-auto version, that would utilize a paint gun filled with fuel hooked to a compressor which would spray mixture into the main firing chamber. But clearly this idea needs more refining.

Image

That's it guys!
Sorry for the long post. Tell me what you think, would it work or not, is there a way to improve it or if something has to be redesigned. Thank you!
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Re: Spud gun powered by cooking oil?

Unread postAuthor: hectmarr » Sat Nov 16, 2019 4:19 pm

Hello! :)
At first glance the system seems quite complex in general. In my opinion, shaping the mix is going to be quite difficult and inaccurate, as I say, at the first sight of its publication. The issue of ignition is unnecessarily complex, having a small piezoelectric lighter that instantly sparkles when you press it is inexpensive and does not need a battery. I would try to simplify, and if the liquid fuel complicates, use gas to load lighters, pure butane, which is already gasified and you can measure it quite accurately. It is my idea only. :roll:
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Re: Spud gun powered by cooking oil?

Unread postAuthor: Doctore » Sun Nov 17, 2019 11:12 am

hectmarr wrote:Hello! :)
At first glance the system seems quite complex in general. In my opinion, shaping the mix is going to be quite difficult and inaccurate, as I say, at the first sight of its publication. The issue of ignition is unnecessarily complex, having a small piezoelectric lighter that instantly sparkles when you press it is inexpensive and does not need a battery. I would try to simplify, and if the liquid fuel complicates, use gas to load lighters, pure butane, which is already gasified and you can measure it quite accurately. It is my idea only. :roll:


To tell you the truth, I also thought that there might be issues when it comes to mixing, especially if I was to use thicker fuels. That is why I thought that this ignition setup would be better for the job, all that thermal energy situated near the exit point plus additional air supplied by pumps.
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Re: Spud gun powered by cooking oil?

Unread postAuthor: hectmarr » Sun Nov 17, 2019 2:25 pm

What I can contribute based on my little experience in making mixtures with liquid fuel, is that finely pulverizing the fuel helps, but to burn it well in air, it has to be vaporized. I have checked it on some weapons of alcohol, combustion, which I have built. Perhaps the heat generated by the lighters helps you vaporize the liquid fuel. You have to do tests on this aspect and see the advantages and disadvantages.
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Re: Spud gun powered by cooking oil?

Unread postAuthor: D_Hall » Mon Nov 18, 2019 1:53 am

hectmarr wrote: I would try to simplify, and if the liquid fuel complicates, use gas to load lighters, pure butane, which is already gasified and you can measure it quite accurately. It is my idea only. :roll:


At the pressures he's talking about, butane is no longer gasified. Gonna need to go with something lighter (propane/ethane/methane) if you want to avoid liquid fuel.
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Re: Spud gun powered by cooking oil?

Unread postAuthor: jackssmirkingrevenge » Mon Nov 18, 2019 7:05 am

Spud gun powered by cooking oil?


This sounds like something you would come up with in a desperate wartime situation where propane is in short supply.

Has anyone ever actually made a spudgun that successfully used automotive fuels?
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Re: Spud gun powered by cooking oil?

Unread postAuthor: hectmarr » Mon Nov 18, 2019 9:22 am

I've tried gasoline, but I've preferred alcohol because the smell of gasoline is very strong and leaves the combustion chamber with sticky residue ... disgusting, but it shoots. I tried it on the small combustion gun, and on two small launchers, which I made at the beginning, with the same video system, but smaller.
This boy does the same, and uses gasoline in his combustion launcher, which works like my weapon.
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Re: Spud gun powered by cooking oil?

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Re: Spud gun powered by cooking oil?

Unread postAuthor: jackssmirkingrevenge » Mon Nov 18, 2019 9:50 am

I've tried gasoline, but I've preferred alcohol


I agree, the gasoline hangovers are terrible :lol:

This boy does the same, and uses gasoline in his combustion launcher, which works like my weapon.


That is very impressive!

There really is a lot of energy in gasoline, I'm reminded of this experiment from the fantastic "The Secret Life of Machines" series where they compare the energy in a teaspoon of gunpowder with a teaspoon of gasoline using a beer cannon:



(starts at 2:50 since I can't embed with a timestamp)
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Re: Spud gun powered by cooking oil?

Unread postAuthor: hectmarr » Mon Nov 18, 2019 10:35 am

This is the old project. It was for a double combustion gun with double chamber. At the time, it shot 6mm bb. He is currently missing the cannon.
By pressing the piston forward, and locking the rod with a bolt type system, you can have some compression of the mixture, (whatever you can do with force),
I am thinking about this.
...donde comparan la energía en una cucharadita de pólvora con una cucharadita de gasolina usando un cañón de cerveza:

AWESOME! It's my weapons day class! :bounce:


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