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Small autonomous hybrid

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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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Fri Nov 17, 2017 8:34 am

I'm looking and analyzing what you tell me about the pressure regulator, trying to understand.
The interesting thing about this possibility is to be able to deduce the real explosion pressure. I have been able to empirically calculate the combustion pressure, raising the pressure of the valve until when it explodes it will not open. For 2 bar compression, with a 4% mixture of pure butane, it is about 17 bar. A little more than 8 times. Of course, the combustion chamber must withstand blockage. In my case I worked, as I said before, with just 2 bars to be able to "measure" this, so the integrity of the camera was guaranteed.
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Re: Small autonomous hybrid

Unread postAuthor: jackssmirkingrevenge » Fri Nov 17, 2017 8:42 am

Interesting indeed, have you tried modelling the system in HGDT to see it the theory matches your practical results?

Regarding the regulator, you don't need to make your own, something like this is very cheap and allow you to adjust the output up to 10 bar.
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Fri Nov 17, 2017 9:21 am

Something like this...
In line "A", pressure according to the air pump. Line "B", pressure limited by the regulator.
I have a pressure regulator. I just bought it a short time ago. I'm going to try to see how it works. Thank you very much Jack.
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Re: Small autonomous hybrid

Unread postAuthor: jackssmirkingrevenge » Fri Nov 17, 2017 9:30 am

Yes exactly like that!
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hectmarr wrote:You have to make many weapons, because this field is long and short life
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Fri Nov 17, 2017 10:05 am

Tested and working :D :D
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Sun Nov 19, 2017 6:27 pm

I thought of a valve that works the same as the video, but simpler to build. I was trying this drawing, and it works well. The orange color, in the diagram, is a circle of soft silicone. It is the only mode that seals as soon as air is pumped on both sides. This allows the pilot to seal with very low force. The edges where they support are 1mm wide, the central and the outside, to increase the sealing pressure. When the explosion occurs, and the piston opens to the right, the air from the pilot section escapes through the same orifice through which the combustion gases escape. The piston is released as long as there is no pressure. All you need is an air pump that has the flow rate needed for the start of the seal. Luckily the one I'm using is enough. When the piston is open, and one begins to pump air, what comes out of the play between the piston and the casing, should be less than what enters from the air pump. Does not use any oring. Use a check valve on the air inlet that is not drawn.
I add one more drawing. For the silicone piston seal I have used sealer for high temperatures, (Fastix, red color). I'm waiting for it to dry completely, 24 hours at least, to try.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Wed Nov 22, 2017 7:43 am

I have worked on this simple design that is practically the same as a common piston valve. The tests were very good, it works as I expected and even better. The "extra" advantage that I obtained is that after the explosion the combustion chamber with a partial vacuum, which will undoubtedly favor the burst piston of burned gases, work with a spring of little force.
The pilot area remains at atmospheric pressure and the valve piston is stuck to the transfer hole that comes from the combustion chamber through this vacuum. I am currently using, to test, a combustion chamber without a plunger to simplify. It is very easy and quick to build, about 2 hours but ... what takes is the setting of the resin and the silicone ... exercise of superior patience.
I publish these results here, because they are works for this project of the small hybrid weapon.
Another modification that I made is to increase the width of the piston seat to 1.5mm because with 1 mm as I was thinking, the silicone starts to get hurt by the sealing force. I have manufactured the valve directly inside the tube of the combustion chamber, and this simplifies things even more.
The partial vacuum is due to the fact that when the combustion gases leave the exhaust at high speed, the inertia that they provoke causes it to drag part of the atmosphere remaining in the combustion chamber to atmospheric pressure, causing a suction. In fact, this is what loads the fuel mixture into the pulso-jet engines. I was looking for the explanation 8)
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Re: Small autonomous hybrid

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Re: Small autonomous hybrid

Unread postAuthor: jackssmirkingrevenge » Wed Nov 22, 2017 9:19 am

Very good, again it's impressive how you manage to make such innovative and high performing experiments with such basic materials and tooling.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Wed Nov 22, 2017 10:08 am

jackssmirkingrevenge wrote:Very good, again it's impressive how you manage to make such innovative and high performing experiments with such basic materials and tooling.

It's my damn curiosity that I'll have to muzzle a little. My mother idea was to quickly build very basic things and shoot, play, nothing more. Extremely interesting about the spud gun in all its variants.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Tue Nov 28, 2017 8:58 am

Upgrade.
After doing a lot of tests with the simple piston valve, it happened that when I went from 2X to 4X which is the maximum that I can get with this test combustion chamber, the piston does not release the air from the pilot and the valve is closed. leaving it impossible to clean the combustion chamber. The solution was to eliminate the check valve and connect as a whole feed back. It is in the drawing. It happens that after the explosion, when the pressure in the combustion chamber drops, the compressed air of the piloted section returns to the combustion chamber, being totally depressurized. This happens because the volume of the combustion chamber is 140 ml versus 8 ml of the pilot. The pressure disappears and the chamber and the pilot remain at atmospheric pressure.
On the other hand, a separate issue, you can leave the combustion chamber no clean. I have discounted the volume of the combustion chamber and I have dosed the gas for this amount of fresh air, and it explodes perfectly. Logically, less fuel is burned.
The proof is like this:
The volume of the combustion chamber is 140 cm3. When the gas needed for a clean combustion chamber is calculated, the quantity is for 2X 140 ml x 3 = 420 clean air ----- at 4% = 16.8 ml butane.
If, after exploding, the combustion chamber is not cleaned at all, it is as follows: 140 ml x 2 = 280 ml of clean air ------- 4% = 11.2 ml butane. Works correctly.
It is obvious that the more "X" has compression less the loss of fuel to burn. I mean that with 2X 1/3 of fuel is lost, but at 4X, 1/4.
This possibility is interesting because the weapon does not need a cleaning system, simplifying much the whole construction, although some energy is lost.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Tue Nov 28, 2017 10:01 pm

Some images of the piston and the seat of the test valve. In the last photo you can see how the rubber was destroyed by the sealing pressure. I have already changed this element for high temperature silicone, harder and I think if it will hold without deforming.
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Re: Small autonomous hybrid

Unread postAuthor: jackssmirkingrevenge » Wed Nov 29, 2017 5:12 am

Fantastic!

This is really some of the most advanced work I've seen done in the field of repeating hybrids in years, bravo! Even your check valve is enthusiastic about it :D

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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Wed Nov 29, 2017 7:30 am

My check valve seems optimistic and alcoholic or its cartoonist? :shock:
When I have time, I'll leave the video of how it works, to show you and talk a little about these nice things.
What I find interesting is that everything has been simplified a lot, but I have to do more tests before trying the prototype 3 that is "inflate and shoot" a step before a semiautomatic. I have worked on the pneumatic circuit, on paper only, and there are possibilities for it to work. It would be a system derived from these autonomous hybrids. I will post in the other post something about this so you can give me your opinion and your criticism.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Fri Feb 09, 2018 6:36 pm

Try this simple design, very easy to build, and I tested it at 4x. It works very well.
The idea is to integrate to simplify. In this case, the piston responsible for sweeping the burnt gases after the explosion of the mixture of the hybrid, is responsible for compressing the spring, (hard), in "A". When the pressure increase occurs due to the expansion of the hot air, the same piston moves back until it opens the output transfer that is coupled to the firing barrel, "B". Then, a small auxiliary valve opens that allows the piston to return and clean the chamber very quickly. I will upload some photos to clarify this issue.
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Re: Small autonomous hybrid

Unread postAuthor: hectmarr » Mon Feb 12, 2018 8:52 am

Images 1 and 2 are from the recent test.
Image 3 is a new one that I am building. 8)
This has double spring. One is to return the piston and clean the combustion chamber, it is the thinnest. The other, the largest, is responsible for retaining the piston in its position when compressing the air-fuel mixture. The small spring runs inside the large spring, which is very hard. When combustion occurs, the pressure peak further compresses the large spring, and the outlet orifice is opened.
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