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Hello !!
I was thinking about making a small, handheld semi-automatic.
I will try my best to expand this idea
Project of a semi-automatic hybrid, topic I planted
In another post, but briefly. I have prepared some simple drawings
To explain to me on this question.
It works like this: 8)

The propellant of the air-fuel mixture compression system is propane, which is also used as a hybrid fuel.
The idea is to use the pressure energy of propane in a tank (about 7 bar at 15 C) to compress the hybrid mixture, leaving all the energy of the deflagration of this stoichiometric mixture in the combustion chamber , To boost the ammunition of the weapon. The system uses, in short, the heat and pressure energy of propane.
The mechanism uses a classic double-acting pneumatic cylinder, and a 12 volt 5/2 monostable solenoid valve.
In diagram "1", position "A", as the larger piston moves to the right, the suction of the combustible air mixture is produced in the lower piston chamber (diagram "4" Gas meter).
When the larger piston reaches the right end, the rod actuates an electric switch that changes the position of the solenoid valve 5/2, and the entire stem assembly and the two pistons move to the left, ("B" position of the diagram) , The compression of the mixture being produced in the combustion chamber of the smaller piston.
The pneumatic lock actuated by the pressure of the propane enters the groove of the stem and this does not let it move when the mixture blast to the right, but to the left. This is necessary to allow the complete cleaning of the combustion chamber. It is a solid steel lock actuated by a pneumatic actuator with its own piston and a spring to return to the unlock position.
After the explosion of the mixture, the pressure in the larger piston forces the smaller piston to completely clean the combustion chamber, at which point, and in that position, the rod actuates another electric switch, initiating another cycle of Suction mixing and compression, automatically.
From the area ratio between the two pistons, the desired compression level is achieved, and this also depends on the gas pressure.
The propane tank, a MAPP bottle has a pressure regulator so that the system does not suffer from inaccuracies due to increases and decreases in pressure, due to variations in ambient temperature.
Diagrams "2" and "3" describe the ammunition loading system, driven by propane pressure, (has its own pneumatic actuator), and the adjustable shut-off valve of the combustion chamber.
This ammunition loading system has already been tested and works perfectly, just like the gas meter and the gas exhaust valve. Only need to build and test the double-acting pneumatic cylinder system. I am waiting for the arrival of the solenoid valve I bought recently.
The time between each shot will be approximately 05 seconds, which I think is acceptable. It will be the only way not to cut discs from rupture and to trigger the air pump, although it will "waste", a little gas. I have a 20 kg tank of propane to refill the mapp bottle, so I do not think it's a big problem.
It's an idea of ​​how to make a semiautomatic hybrid, which I'll try to build

An ambitious project but having seen what you're made so far, I believe you can pull it off

Seems a bit wasteful of propane though, I don't think you want to be firing this thing in an enclosed space...

Hi Jack ! You are always in the answers, to talk a little about these things. Thank you very much.
It's really just as you say. Precisely, I was analyzing this issue of propellant spending today and it is high.
I'll tell you what I found out about this.
According to information I read on the internet, 1 liter of liquid propane is transformed into approximately 270 liters of propane gas.
This plan that I think, for each shot would spend at least 1 liter or 1.5 liters of propane in the gas phase. I deduce that with a tank of gas mapp and 500 ml of liquid propane inside, could make about 60 shots ... That is the reality. Otherwise, it would be VERY dangerous not to take the precautions common sense dictates with this subject.
This is one of the very weak points of this plan, I do not know ... We will see how to minimize the amount of propellant as much as possible
I was inspired by the green gas that is mostly propane used by those who shoot airsoft replicas, which is why I am considering this option. What do you think of using CO2 with a pressure regulator to move this?
I am analyzing the possibility of using, to build the pneumatic cylinder, a motorcycle damper, I mean to adapt it. Buying one is not an option for me because in my country the price is very high, by the dimensions, approximately 45 mm in diameter of the plunger and 200 mm stroke of the stem, which is necessary to compress 180 cm3 of mixture to about 6 Pub.
Well I will comment here on the progress that will be slow for sure. If it works ok, and if it does not work in a practical way, think about something else and try again. Greetings to you

A possible solution to economize propellant would be to use a single acting cylinder with spring return, and a solenoid valve 3/2.
It is necessary to consider the strength of the spring opposing the force of the larger piston, in the compression stage. The consumption of propellant would be reduced by half.
This would affect as I understand this, to reduce somewhat the speed of the aspiration - compression cycle, increasing slightly the time between each shot, although this question is not so serious, as long as the time is not too long.

I still think that the compression ideally comes from a fixed source, like a spring or closed gas piston - because a hybrid combustion gives a lot of energy disproportionate to the compression of the gas mixture before combustion, and this energy can be used to reset the compression mechanism for repeated firing.

jackssmirkingrevenge wrote:I still think that the compression ideally comes from a fixed source, like a spring or closed gas piston - because a hybrid combustion gives a lot of energy disproportionate to the compression of the gas mixture before combustion, and this energy can be used to reset the compression mechanism for repeated firing.

Yes, I have analyzed your drawing and it would be much more comfortable to build than what I am planning to do.
Of course, that using the same energy of the explosion to compress the mixture is possible although the expense would be very high.
In a turbojet, (I am a veteran aircraft model and have built turbines, pulsoractors etc), the compressor consumes two thirds of the total energy generated. The remaining 30% is used to propel the vehicle. It seems to me, this would be very similar.
I imagine, if you compress to 10X, the weapon will fire like a 3X ... That is the biggest problem of this system, although it is totally possible.
In an automatic firearm, as you say, this system is used, that is, to take a portion of the gases resulting from combustion to recharge the weapon, but it is an auxiliary system, which consumes much less energy from the explosion than Intended to propel the projectile. At least I get it. A hybrid is an "engine" that runs a fraction of a second.
It would be interesting for those who really know about these issues to bring some clarity and a numerical approach to these processes.
A question about this system that you propose. How to clean gas burned combustion chamber? As I tell you, I'm considering and analyzing it as another option for a semi auto hybrid.

Watch this. It inspires ....

In a turbojet, (I am a veteran aircraft model and have built turbines, pulsoractors etc), the compressor consumes two thirds of the total energy generated. The remaining 30% is used to propel the vehicle. It seems to me, this would be very similar.
I imagine, if you compress to 10X, the weapon will fire like a 3X ... That is the biggest problem of this system, although it is totally possible.

I don't think it would be quite so disproportionate. Look at recoil operated firearms (click for non-medieval gifv image):



The projectile is light and accelerates quickly, most of the recoil operation happens well after the projectile has left the barrel. You won't get more energy firing a bullet from a closed action than from a blowback one. Essentially you would be using energy that would otherwise have been "wasted" by making the weapon mass recoil.

A question about this system that you propose. How to clean gas burned combustion chamber?

One option could be to replicate the bore evacuator that modern tank guns use. Some of the exhaust gas flows into a chamber, when the pressure in the barrel drops the gas exits through angled ports that create a gas flow which cleans out the bore.



Following on from the idea, I wonder if it would be possible to create a "diesel" type repeater.



A spring compresses a piston which heats the mixture sufficiently to ignite the fuel, which fires the projectile and also re-cocks the spring.

I understand what you are proposing to clean the combustion chamber of burnt gases.
Personally I am inclined to consider a simpler method of designing, such as the cleaning piston that leaves the combustion chamber with zero volume. That type of system you describe, needs tight calculations to ensure that flue gas cleaning is 100% effective. Equally, it is an option to achieve this.
With what you dirty of the auto ignition, I think that, yes, this can be done, in fact it is seen in the image that you uploaded. I do not know what the minimum pressure will be in relation to the type of fuel.
A question. Has not this been done already? I mean a semi automatic hybrid weapon? If we could get a plan, to adapt and build directly, this question would be a quick and proven solution.

hectmarr wrote:A question. Has not this been done already? I mean a semi automatic hybrid weapon? If we could get a plan, to adapt and build directly, this question would be a quick and proven solution.

Not that I know of, the closest I have come to it is to use pre-loaded cartridges which have been documented in detail in this megathread: http://www.spudfiles.com/hybrid-cannons/topic19504.html

To me, this is the most practical way to do it because all the mixing apparatus is kept away from the launcher, and of course because you get to have awesome shell ejection!

[youtube][/youtube]

I never made a magazine feed for hybrids but I know it can be made to work with pneumatics:

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By the way, you might find some interesting discussion here.

I had seen this work, awesome indeed !.
In my opinion only need to put everything you built in a wood with a butt and a trigger, make about 5 cartridge and to try. The most difficult, for this idea of design that you developed, as I see this question, is realized.
I personally, I have to go for something much simpler to build, even if it is not very orthodox or standard. All the work that I have done in this field of spud, have neither lathe nor welding of any kind. This is my challenge. In the future I will send to build what is necessary for the small autonomous hybrid, but as an exception.
I have tired of searching everywhere, even on the deep web on this subject and apart from here in Spudfiles, I have found absolutely nothing. You are a pioneer, no doubt.

I have tired of searching everywhere, even on the deep web on this subject and apart from here in Spudfiles, I have found absolutely nothing. You are a pioneer, no doubt.

In this book, mention is made of the "Croker Gun", a proposed design that used a fuel/air mixture. No details are given but clearly the idea is almost as old as the internal combustion engine. Nothing came of that, but what are effectively hybrid guns are being considered as replacements for powder burning naval guns.

Here's one vaguely related, an Electro-Thermal-Chemical revolver prototype:



Nothing really to do with fuel air hybrids as we know them in terms of propulsion, but the revolver configuration would be one way of practically achieving repeating fire from a hybrid.

Full video:

[youtube][/youtube]

edit: some things you might want to look at to help with your research:

How combustion nailguns work

Tippmann C3 Combustion Paintball Marker:



gifv link

Tippmann C3 Patent

Good information all this. Watching shoot that anti-missile cannon is very inspiring. Thank you Jack.
I have been defining the dimensions of the probable hybrid semi auto. I mean calculate exactly the volume, area, and dimensions needed, and defining some aspects, in more detail.
Hopefully later in time I can do it, it would be nice to have something like that at home to play for a while I will put here what is left clean for you to consider and give me your opinion.

I was checking the numbers of the possible prototype to build.
These are the measures and values ​​that could have the experiment.
As I did the basic numbers, for each shot made, they would be spent
1.6 liters of propane in the gas phase, which is half that before.
The total volume of the larger cylinder is 411 cm3 and at 4 bar are
1.6 liters, approximately.
With a can gas type mapp with 400 gr of propane, can be realized
About 100 shots, which seems to me
acceptable.
The spring which has as its mission to return the stem has been
Considered with a force of 10 kg, fully compressed. This force
Is subtracted from that exerted by the gas pressure on the piston greater than
Is useful for compressing the explosive mixture.
78 kg less 10 kg remain 68 kg to generate compressive force.
It would have 68 kg in the axis that unites the two pistons, that applied
In the area of ​​9.6 cm2, compress the mixture to 7x, which is sufficient
To try to prove the prototype in reality.
The propane tank has a pressure regulator at the outlet
To stabilize the supply pressure at 4 bar.
It is an option, if necessary, to heat the tank to avoid
The fall of pressure by temperature drop, when the gas
While leaving the warehouse.
Where I live, near the tropics, the temperatures are high, in summer they roam
35 ° C - 40 ° C normally, and in winter, not lower than 10 ° C climax
warm.
The 200 cm3 mixture of propane and air, in the smaller compression cylinder,
Is confined in approximately 28 cm3, occupying 3 cm of length of
This smaller cylinder.
In the diagram it can be seen that the locking mechanism, for securing the rod
Which holds him firm so he does not back down during the blast,
Is between the two pistons, to save space. The overall design with
A single acting pneumatic cylinder, is more compact and saves propellant.

This is what there is ... as someone said, in mechanics there are no miracles.
To shoot with this weapon things are very simple. Fill gas tank
Load about 20mm 5.5mm ammunition and use. This is the good thing about the system.
The downside is that it tends to be bulky, at low propellant pressures.
Another disadvantage is that you have to be cautious with letting the propane expelled
In closed places. Pulling outdoors is the right thing to do. If used in enclosed spaces,
Let air and not do 50 shots in a row ...
I have observed that the temperature of the combustion chamber increases rapidly if the
Shots are followed. This issue can become a problem.
I calculate that you can shoot every 2 seconds at least, this way everything can
Warm up enough. From the tests I will have the experience and the solutions.
If functioning properly, CO2 can be used as a propellant, and propane
In very small quantity just to burn. In this way, you could compress
The stoichiometric mixture to many more "X". This is a real possibility.
It turns out that it is easier, to test, to use propane gas, mainly because
I have a lot, including the pressure regulator, and two mapp bottles to refill.
Still missing, several solutions of how to build the test machine. For the moment
I am in the task of getting the materials, arduous task indeed

Diámetro pistón menor 3,5 cm

Area pistón menor 9,6 cm2

Volumen 200 cm3

Longitud 21 cm

Presión 7 bar

Volumen de la mezcla comprimida 28,6 cm3





Diámetro pistón mayor 5cm

Area pistón mayor 19,6 cm2

Presión 4 bar

Fuerza 78 Kg

Volumen 411 cm3

Longitud 21 cm

Volumen gas expulsado por ciclo 1600 cm3

I was also analyzing how to solve the problem that the sealing valve,
Does not let out all the burned mixture when the explosion occurs, because the force of the spring closes very fast.
The valve, once opened by the pressure of the explosion, can not close again as quickly as when
Has a very hard spring, because it loses all the force when the gas escapes by "B", when moving towards the left
In the diagram, allowing the exhaust of all gases from the combustion chamber, and allowing the smaller piston, the
Which compresses the mixture, reaches the bottom of the cylinder, totally cleaning burnt gases.
"A" is the pressure inlet, which is applied in an area larger than that of the seal element, produces
The force required to firmly seal the combustion chamber.
The spring in this case is soft, only to seal the seal element smoothly.
I've seen this type of valve in some weapons I saw in the forum, and in Spud wiki. The only difference, for the specific case
Of the project, is the depressurization. I imagine it should work properly, I have to do the tests for this.