Spud gun powered by cooking oil?

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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Doctore
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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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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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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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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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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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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?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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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.
[youtube][/youtube]
Ideas don't make holes. The weapons yes! ;)
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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:

[youtube][/youtube]

(starts at 2:50 since I can't embed with a timestamp)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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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:


[youtube][/youtube]
Ideas don't make holes. The weapons yes! ;)
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Tue Jan 14, 2020 1:33 pm

Has anyone been experimenting with this concept any further?
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Fri Jan 17, 2020 4:02 am

Doctore wrote:
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!
This is an interesting concept, but it appears to be a much more expensive and complicated way to build a combustion gun without a clear advantage. The ignition sources are very suboptimal these days when we have very cheap electric ignition devices (even walgreens have "flameless lighters" aka stun gun components for <20 bucks), and reloading looks horribly complex; really think about how you'd have to replace that rubber plug every time you fired it. That seems tiresome.

On a more basic level, the entire idea here is about how to make a thick liquid fuel into one capable of gaseous ignition, and at the core of it the problem is surface area. With sufficient volume and a good atomizer nozzle you could get cooking oil into the right fuel:air proportion that it'd ignite and fire a spudgun. Not to be a jerk, but this design with pressurized air behind a small volume of liquid and a cork -no nozzle- does not mean that the liquid would become an aerosol and meet that ratio; rather it would take the path of least resistance and likely just splatter into the next chamber. It'd be hard as hell to combust.

I made a version of the semi-auto idea you were in progress of getting to in 2007 and it was insanely dangerous (the chamber hooked up with one solenoid connected to direct oxygen, the other propane) but it did work very very well (until the solenoids burnt out, heh)
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Fri Jan 17, 2020 3:16 pm

PCGUY wrote:
Tue Jan 14, 2020 1:33 pm
Has anyone been experimenting with this concept any further?
Hello PCGUY :) :)
I have not experimented with this concept yet, as I do not have the proper tools and resources. In my mind, I went through this idea many times. There are many brilliant individuals here on Spudfiles and if someone decides to experiment with this concept, I am here to help.
NeoSpud wrote:
Fri Jan 17, 2020 4:02 am
This is an interesting concept, but it appears to be a much more expensive and complicated way to build a combustion gun without a clear advantage. The ignition sources are very suboptimal these days when we have very cheap electric ignition devices (even walgreens have "flameless lighters" aka stun gun components for <20 bucks), and reloading looks horribly complex; really think about how you'd have to replace that rubber plug every time you fired it. That seems tiresome.

On a more basic level, the entire idea here is about how to make a thick liquid fuel into one capable of gaseous ignition, and at the core of it the problem is surface area. With sufficient volume and a good atomizer nozzle you could get cooking oil into the right fuel:air proportion that it'd ignite and fire a spudgun. Not to be a jerk, but this design with pressurized air behind a small volume of liquid and a cork -no nozzle- does not mean that the liquid would become an aerosol and meet that ratio; rather it would take the path of least resistance and likely just splatter into the next chamber. It'd be hard as hell to combust.

I made a version of the semi-auto idea you were in progress of getting to in 2007 and it was insanely dangerous (the chamber hooked up with one solenoid connected to direct oxygen, the other propane) but it did work very very well (until the solenoids burnt out, heh)
Hello Neospud :) :)

I agree with you that this system is both expensive and complicated, but I believe that this system can be improved and that bigger amount of energy can be produced. I also agree that rubber plug can be omitted and that mechanical nozzle type thing can be designed. It was easier to draw rubber plug in paint :lol: :lol: .

As for the cooking oil, it has been just a funny idea. If this device could burn cooking oil it could use pretty much any flammable liquid. I will remind you that ideally clean volatile fuel like alcohol would be used, gasoline would be my second choice.

When it comes to the ignition system, some have already suggested to use proven electrical igniters. I would like to try modified car cigarette lighters and similar ignition systems, as if to dump thermal energy into the main firing chamber prior to shooting. I believe this would increase the chance for the chemical reaction to take place.

A few days ago, I was thinking about another thermal ignition system which would be comprised of quartz heater tubes. This system would dump even more infrared thermal energy since it would be powered by alternating current. Here are some pictures of my bathroom quartz heater to get the idea.

Image

Image

In this case, the main firing chamber would be a long and narrow tube made of thick metal. Two or three quartz heater tubes would be placed. I have no idea how durable are these quartz tubes, but they are not that much expensive. Of course, the main firing chamber must be designed so that these tubes can be easily replaced if necessary.

I am not able to start on this project anytime soon, but trust me this thing is going to be assembled.
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