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I am working on building a hybrid, and I want multiple shots. I was thinking of making my own separate air tank for it out of sch 80 steel pipe, but I found something that might be better: Bernzomatic pure oxygen cylinders. It looks like it's slightly larger than a propane or MAPP cylinder, but I think it contains a fairly large amount of oxygen. Does anyone know what the output pressure of these is (90 psi, like propane?), and how many shots you can get out of one in a 3-5x hybrid?
They are filled to around 400 psi. You should know the difference between oxygen and air before doing something like this. Oxygen has 5 times the oxygen content of air so things will burn much more rapidly, violently and easily. Many oils will spontaneously combust in it's presence. A google search on oxygen hazards would be a good idea first.
The bottles don't last long when using them with a torch but I'm not sure how long they last in this application. If moonbogg doesn't reply you might want to drop him a PM seen as he used these bottles in the striker.
yes, I actually emailed him about that once (easier than PM-ing him on my iPod touch), I was wondering what was in that third cylinder on the Striker. So I'm guessing that that quantities to put into the chamber would be much smaller since it's pure oxygen. Something like that would probably last quite a few shots.[/quote]
A mapp cylinder (or propane), the oxygen cylinder..the third one you're thinking of is probably the chamber .
Just make sure you do plenty of research on oxygen hazards first. Tech will probably show up and post photos of exploding regulators.
Whoops, I meant the second cylinder.
Is there a different equation for calculating how much "pure" oxygen is required in a hybrid? When you said that they have 400 psi earlier, do you mean that I will need a 400 psi-rated regulator to bring the pressure down? Also, how big (LxDia) are those things? 1.1 cubic feet sounds like alot.
The formula for figuring the "Mix" isn't difficult. The hazard is assuming the power simply expand in a linear fashion.
Many combustible gasses have a lower explosive limit (LEL) and upper explosive limit (UEL). These explosive limits are based on a mix of AIR. In an oxygen enriched atmosphere, these combustion ranges change.
In air propane has a sweet mix near 4%. In Oxygen it is a lot wider.
In regards to power, the energy of combustion is limited by the fuel. In an oxygen atmosphere, being 5 times richer in oxygen there is enough oxygen to burn 5X more fuel in the same space. If you use this partial knowledge, you can get killed. If you use oxygen in a hybrid, getting 25XI the fuel and oxygen in this chamber over a metered propane only takes 4 bar.
The lack of the rest of the air that takes some of the heat of combustion enables faster combustion and higher temperatures. This is called an explosion. Experimenting with Oxygen enriched mixes often leads to disaster. Be very careful. I do not recommend using Oxygen in a Hybrid at all and in a combustion only if it is properly manufactured out of malleable steel.
As far as the bottle, Oxygen is not in it like a liquid that boils. It is simply compressed. The 1.1 cu ft is the volume the gas would take at 0 PSI at standard room temperature at sea level. If you deliver the gas at about twice the pressure, it will occupy 1/2 the volume. Needless to say, you won't get many hybrid shots out of one of these little tanks. They are designed for small hobbyist brazing jobs and nothing else. A small 80 cu ft tank or larger is used for welding.
The small tanks are sold as they are safer for casual users as the pressure is much lower as well as the amount of oxygen in it. For serious use, this is a very expensive way to buy oxygen. It would be like buying gas for your car in 12 oz pull top cans. The tank itself is the same size as a disposable propane tank for a hand held torch.
I've already posted photos of exploding regulators.
This is a 1X mix in a party balloon. In a hybrid the pressure increases the power much like using a larger chamber, but due to the smaller space, the flame front burns the entire mix faster (shorter distance).
http://www.youtube.com/watch?v=QF5l4nl1P4U Video for educational purposes only. Do not make these.
Edit I found the photo I was looking for.
From this article;
http://www.thedenverchannel.com/news/67 ... tail.html#
Note, possible prison time for this one.
I haven't counted the shots and haven't used that cannon recently as it is undergoing ignition and gasket changes so I honestly do not know how many shots to expect as of yet. It also depends on what mix you use the cannon at. Using a lower mix might be a good compromise to prolong the usage of the O2. The O2 regulator I use came with a torch kit and nothing other than true oxygen regulators can be used with oxygen. Using any other type of regulator for oxygen can instantly explode upon fastening it to the oxygen tank. You don't have to bang it, drop it, light it on fire or anything. It can actually explode instantly from the friction of screwing it on and from the pressure of the O2 interacting with oils, greases and contaminants. If using O2 tanks proves to be an expensive operating cost I may change to good old air and replace the O2 tank with an aluminum air tank of similar size. Air is cheaper, clearly available to everyone and safer.
Like Moon said any oils in threads, valves or other equipment in the line will spontaneously combust in oxygen. This is why things for oxygen use are cleaned in mineral spirits then washed in a degreaser. All oxygen line equipment will ALWAYS note to never use oil.
Many rubbers will also decay rapidly in the presence of oxygen.
How about these? They are intended for LPA use, so a larger cylinder (or small chamber) would be required. Extremely lightweight though.
So say if I used a 2x mix with regular air-with the same amount of pure oxygen instead it would be a 10x mix? And at normal atmospheric pressures, it would be a 5x mix? Actually sounds pretty efficient to me. Where did you get your regulator? As with oils, could I still use a piston valve with silicone or another lubricant and o-rings? And don't worry, I have already read several articles on oxygen safety.
You missed the part about the FASTER combustion. This is not the same as a 10X mix. It's missing a huge chunk of nitrogen to regulate the burn rate and peak temperature.
In the safety stuff, the rubber and lubricant oils don't mix with oxygen enriched mix under pressure. Have you dealt with the DDT?
Technician is right about it combusting much faster. When I first test fired the cannon, I actually thought it had exploded and I was about to do a body parts check once I was no longer blinded from the flash. The blast was loud and, due to lack of a better word, very SHARP and SUDDEN. In other words it appears to be POWERFUL.
I got the regulator from Lowes in a torch kit package that came with mapp gas, oxygen, a mapp valve and oxygen regulator as well as the torch itself. It was about $50.00. it is the ONLY cost effective way to obtain an oxygen regulator that I myself have discovered. They are usually very expensive and with the kit, you not only get the regulator, but everything else as well.
I use oils and lubricants and rubber in the cannon and there is no problem with it. The issue is with the oils coming in contact with the extreme pressure of oxygen that is in the oxygen tank itself. The oils in the chamber won't explode being exposed to the low pressures of oxygen that is needed for low mix hybrid operation. Once in the chamber, the oxygen is SUPPOSED to "explode". Thats what a combustion chamber is for and dieseling oil isn't going to bust a strong metal chamber so long as there isn't tons of oil in there. The oil tends to burn off, requiring maintenance of the piston itself. This is at least what I have discovered in my own experience.
I have found oxygen regulators for $30 on harbor freight's site. I am thinking about making this more of a combustion than a hybrid, injecting the oxygen and fuel at atmospheric or only slightly above atmospheric pressures, but still sealing the chamber with a burst disk or piston valve.
I don't think this calculation would be right, but I'm going to ask anyway, just to be sure. If a 5x hybrid requires 200cc of air to fill the chamber, would it require 40cc (200 / 5) to fill with pure oxygen? I got the part that it burns a lot faster, but just tell me if this calculation would work at all.
edit: I actually calculated the fuel mixtures using the formulas for propane and MAPP. For propane with pure oxy, it's 20%, with MAPP it's 21.9%. This is assuming you are operating at atmospheric pressure (1x). For higher mixes, I am going to work from propane's 1:5 oxygen ratio, since it accounts only for oxygen atoms.
Sorry for double post, wouldn't let me edit - Moonbogg, where did you get the $50 torch kit you mentioned in your earlier post? I couldn't find it on Lowe's website.
I walked in the store to buy it. I did find this link to a random place that sells it though. Also, McMaster-Carr has them of course (78645A39). Its $60.00 from there though which is no surprise.
I've seen those in welding supply places, not in big box stores such as Lowes or Home Depot. I have a full size torch, so I didn't play much attention to the kit. The kits are for sale in welding supply shops that carry the disposable Oxygen for the kits. If you use a lot of Oxygen, the refillable cylinder is MUCH cheaper. The initial cost of the high pressure regulator is an investment that with care will last a lifetime. I got mine with a torch I bought second hand.
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