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Hybrid design ideas

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: Alanstone » Thu May 02, 2013 6:39 am

To JSR: " Fair enough but it's smacking of "free energy" to me..."

That is exactly the thought that has been running through my mind this morning. With CO2 it can in reality be nothing more than a conversion of energy. I suppose what keeps catching me is that the heat/pressure relationship with CO2 isn't linear. It escalates. If it were linear it would be easy to recognise that there is only energy conversion taking place between the heat/pressure from the butane/air combustion and the rise in CO2 pressure.

"I would definitely do a side-by-side comparison of a chamber with air + fuel and then CO 2 + O 2 before investing in a fully functional setup."

You are right. Propane burns hotter with oxygen than air though and I think it could be the same for butane so for a comparison the best way to go would be fuel/O2 into CO2 and then fuel/O2 by itself. If the is no benefit the result will be nothing more than the fuel/O2 combustion result + the CO2 pressure (or even less) due to the losses due to restrictions in flow resulting from the CO2 inclusion.

If there is no benefit from CO2 (which is attractive because its safe) then there is definitely a benefit from N2O and that's where I would then focus next.



You did a lot of work with regard to cartridges and you got far. I have gone through that thread a number of times. Its never to late especially now that you have the machines and moar skills.
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Unread postAuthor: jackssmirkingrevenge » Thu May 02, 2013 8:16 am

Just a thought about N<sub>2</sub>O, all it does it provide more oxygen to the mix.

In vehicle racing, nitrous oxide (often referred to as just "nitrous") allows the engine to burn more fuel by providing more oxygen than air alone, resulting in a more powerful combustion. The gas itself is not flammable at a low pressure/temperature, but it delivers more oxygen than atmospheric air by breaking down at elevated temperatures. Therefore, it is often mixed with another fuel that is easier to deflagrate.


If you're filling a chamber with 76% carbon dioxide, 20% oxygen and 4% propane... then you must have an oxygen cylinder.

So... why not fill your chamber with say 83% oxygen and 17% propane :D
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Unread postAuthor: Alanstone » Thu May 02, 2013 3:42 pm

"Just a thought about N 2 O, all it does it provide more oxygen to the mix."

That is true when its in its liquid phase. In its gaseous phase it can decompose into N and O2 under heat and pressure. It is an exothermic reaction. I was sure you had picked that up. Sorry, perhaps I should have made that more clear. I was so focused on the CO2 discussion earlier that I did not switch to this properly.

I don't know how to make those neat links you do but here is a link with more info.

http://www.google.com/url?q=http://www. ... eJxziT7k0w
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Unread postAuthor: jackssmirkingrevenge » Fri May 03, 2013 2:25 am

Granted, it will generate heat during decomposition... but enough to beat filling the entire chamber with fuel and oxygen?

Don't get me wrong, not trying to discourage innovation here, I think this merits further investigation.

I would start off making a simple hybrid chamber, basically small and thick walled tube threaded at both ends, one end capped and one end with a union for a burst disk. I would fit an automotive spark plug ingition system, and say a 3/8" barrel that would take 3/8" steel ball bearings as a consistent and cheap projectile for comparative testing.

I would then obtain regulated bottles of compressed air, carbon dioxide, propane, oxygen and nitrous oxide, and a fine low pressure regulator - and get testing :D

The above represents quite a financial outlay, I don't think you could do it for less than $1000 - but it would be a lot of fun, and the data it would generate would be invaluable to the community.
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Unread postAuthor: Alanstone » Fri May 03, 2013 9:15 am

Touche! For therein lies the rub! :)

A thousand dollars equates to just under nine thousand rand (our currency). There is an arsenal of really amazing weapons to be had for that price. It's not about that for me though. So what I am going to do rather than go the exploratory route is to get to know how to do the math on this thing. One must be able to calculate the outcome. For safety sake also.

For instance I am not only worried about rupture due to pressure I am also concerned that in such a reaction one could inadvertently create a really nasty gas as a by product.

I honestly get that the gains of a "maybe" may not warrant the effort. You are right that a high "standard" hybrid mix does offer all one needs with regard to power too. Getting that mix though is a lot of work. One either pumps your life away to get the pressure or you are tethered to a pump system or a compressed air bottle. My hope in all this out the box thinking was that I could use accumulative effects to do the same thing. A low pressure combustion mix triggering a high volume reaction.

I do still feel this thought process must have merit and at the same time do concede that it just may not be worth it at the end. In any event, I will continue to play with my ideas and hopefully get to the point where my contribution does add to the merit of this fascination of our collective interest. :)

JSR, thank you for your input. I am sh*t sure there are others on this site that could have assisted hugely in this thought process. I have no doubt that in our ranks lies a chemical engineer or two. Yet I do understand that one mans interests may not be that of another. Gets me thinking about BTB: Brother! You are in your own mold and a craftsman for sure! You deserve to be making a living doing what you have posted here. Unique and always special. People should line up to buy your creations.

On a different topic; have you been following the advent of wikiwep? What do you think? I know solar made you an awesome offer (I would have jumped at that!) And I also recognise that you must be on a similar tangent to have so decently refused.

In any event I wish upon you a career which keeps you up late at night and is only interrupted by you having to sleep. And when you wake up the morning you have the excited feeling of a boy who can't wait to get back to playing with his toys :)

While I get to the point of working this one out I am going to put what I have learned thus far to use.

I really respect mpmrla's pneumatic contribution with regard to his .50 and .36 cal qev single shot pneumatic. A really worthy effort. And then in the same vane, cane toad's .25 pneumatic. Very functional and pleasing, both these contributors deserve to be able to ship their products all over the world in small easy to assemble packages. And then the frenchmen! How I wish I could log onto and understand their site! The few which have come onto spudfiles to show their contributions have been exceptional.

Dude I wish I knew what you are working on. If it isn't exceptional I will eat my hat. Don't let North America call to long, f*ck it! Go and live the life you deserve!
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Unread postAuthor: jackssmirkingrevenge » Fri May 03, 2013 2:27 pm

Alanstone wrote:A thousand dollars equates to just under nine thousand rand (our currency). There is an arsenal of really amazing weapons to be had for that price. It's not about that for me though. So what I am going to do rather than go the exploratory route is to get to know how to do the math on this thing. One must be able to calculate the outcome. For safety sake also.


I think that as an individual, the complexity of the variables involved means that you would probably not achieve a representative result, though it could give an indication of which direction development should reliably focus. In any case, there is much to be said against conceiving of a theoretical system which you then couldn't afford to build.

For instance I am not only worried about rupture due to pressure


Most paintball tanks come with a 5000 psi burst disk safety valve. I've never heard of one failing at the normal 3000 psi operating pressure. If you make your disk out of a consistent material mounted in a consistent way, it should always burst at the same pressure.

I am also concerned that in such a reaction one could inadvertently create a really nasty gas as a by product.


Your average automobile is constantly pumping out a stream of noxious chemicals, personally this possibility would be extremely low on my list of concerns.

I honestly get that the gains of a "maybe" may not warrant the effort. You are right that a high "standard" hybrid mix does offer all one needs with regard to power too. Getting that mix though is a lot of work. One either pumps your life away to get the pressure or you are tethered to a pump system or a compressed air bottle. My hope in all this out the box thinking was that I could use accumulative effects to do the same thing. A low pressure combustion mix triggering a high volume reaction.


This is why going with oxygen and fuel alone is worth looking into. Technically, you can have a 5x mix at atmospheric pressure (no hassle with burst disks or valve) by flooding the chamber with oxygen then adding fuel. The only reason I haven't gone down this route is a reluctance to work with pure oxygen.

I do still feel this thought process must have merit and at the same time do concede that it just may not be worth it at the end. In any event, I will continue to play with my ideas and hopefully get to the point where my contribution does add to the merit of this fascination of our collective interest. :)


Looking forward to what you might come up with :)

On a different topic; have you been following the advent of wikiwep? What do you think?


Once you have the ammunition, making the gun is the easy part. This is the great thing about spudguns, because they bypass the need to even touch solid propellant. In that respect, even the best "wiki weapon" is not living up to its name if it still requires firearm ammunition.

I know solar made you an awesome offer (I would have jumped at that!) And I also recognise that you must be on a similar tangent to have so decently refused.

In any event I wish upon you a career which keeps you up late at night and is only interrupted by you having to sleep. And when you wake up the morning you have the excited feeling of a boy who can't wait to get back to playing with his toys :)


I always knew this would be a year of change, I just didn't know how much. All I can say is that the future is bright :)

I really respect mpmrla's pneumatic contribution with regard to his .50 and .36 cal qev single shot pneumatic. A really worthy effort. And then in the same vane, cane toad's .25 pneumatic. Very functional and pleasing, both these contributors deserve to be able to ship their products all over the world in small easy to assemble packages. And then the frenchmen! How I wish I could log onto and understand their site! The few which have come onto spudfiles to show their contributions have been exceptional.


Before I used to think Americans were a little lazy, but now I understand that when you have easy access to firearms, there is very little impetus to innovate. I think this explains the apparent disparity in the levels of ingenuity displayed by the various nationals on this forum.

Dude I wish I knew what you are working on. If it isn't exceptional I will eat my hat. Don't let North America call to long, f*ck it! Go and live the life you deserve!


Lots of projects in the pipeline, more than could ever be completed in many lifetimes, but as they reach fruition they will be introduced to the forum in due course ;) as always, watch this space.
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Unread postAuthor: Alanstone » Fri May 03, 2013 3:12 pm

"In any case, there is much to be said against conceiving of a theoretical system which you then couldn't afford to build."

Prototyping can become a very costly venture. Better men than I have ruined themselves that way. All I was saying was I think I can get a lot closer to viability in design before I start throwing money at it.
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Unread postAuthor: jackssmirkingrevenge » Sat May 04, 2013 2:43 am

Alanstone wrote:All I was saying was I think I can get a lot closer to viability in design before I start throwing money at it.


Can't argue with that :) gentlemen, unsheath your calculators!
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