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New fuel meter concept.

A place to ask general spud cannon related questions.
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Unread postAuthor: Fnord » Thu Oct 18, 2007 12:30 pm

I assumed that it would be common sense to not use a large amount of gasoline in such a meter.
#1 safer
#2 less weight
#3 a few ounces will last a long time.

(And I thought you were being sarcastic in that post, btw. Were you?)

Also, for any real voltages to occur in the meter I think you'd need layer of something metalic on either side of the dielectric(pvc).
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Unread postAuthor: silverdooty » Thu Oct 18, 2007 1:27 pm

i was being a touch sarcastic, i admit. though there is a big difference between the diagram and 3-5 oz. 3-5 oz is definitely not sloshing around like a bomb.

i still stand by most of my precautions. after reading many of the posts on this site, i know there are more less-knowledgeable members than members with chemistry and physics degrees.

in my book it is safety first
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Unread postAuthor: williamfeldmann » Thu Oct 18, 2007 2:29 pm

The pic shows what I considered to be a bit more than 3-5 oz.

@All who have been saying that static is safe and pvc is pressure rated, etc.

Have any of you been filling your car's gas tank and wondered what the sticker on the pump meant when it says to shut off engines? Or to only fill containers when they are on the ground, not in the bed of a truck or on the vehicle? Those are static electricity warnings.

I am a volunteer firefighter and I have seen the aftermath of people not shutting off their cars and pumping gas. If anyone wants to try to prove that your pvc combustion gun can hold more pressure than a steel gas tank on a semi, by all means try, but I have seen craters created by gasoline fumes and the static of someone climbing back into their car on a winter day. The amount of static required to set off such an explosion is far below what your igniters create. You can get enough of a charge by rubbing your sock feet across the carpet in your room.

Play it safe, use the fuel that is already gaseous. If that accidental flame made it to fuel still in liquid form, the heat of the fire, even for the second or two it has oxygen, will easily melt plastics. It's not worth your life.
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Unread postAuthor: silverdooty » Thu Oct 18, 2007 2:44 pm

please read through these and then tell me my precaution aren't just. 17,500 results some with video
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Unread postAuthor: Fnord » Thu Oct 18, 2007 3:34 pm

Ok, I'm going to assume no one actually read my original post.

To everyone:

The fuel in the meter is absorbed into something that won't dissolve in gasoline.
This would prevent gasoline from going everywhere should something go wrong.
I did not draw/label this in the diagram because I didn't feel like it, and was confident that other people would read the notes.

If you are concerned about getting blasted with fuel if the plunger were to pop out, think for a second.
DUH. Put a cap on the end with a hole in the center, like on a bike pump.

THIS IS JUST A CONCEPT.
It probably isn't as safe as propane, but it is a new idea. If we run away from every new idea that isn't completely safe, we might as well never have left the caves.


To William feldmann:
A pvc vessel would have an advantage over a semi truck gas tank because of its size. I don't know what the standards are for truck tanks, but there is no reason a nfs-pw gun shouldn't be able to contain a blast from gasoline.


On a side note, how big did you guys think the meter was? Make it too big and the plunger would get hard to pull.
Gasoline is lighter than water, so 5 ounces might seem like a lot in terms of volume.
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Unread postAuthor: williamfeldmann » Thu Oct 18, 2007 4:07 pm

I understand that you would have some sort of filter/sponge in between where the liquid fuel is and the pump, probably around where the check valve is in your picture. Good idea, but if the check valve doesn't stop the back flow, the sponge or whatever you use won't either. If fumes can get through, fire can get through. Simple as that.

Even 5 oz of gasoline will make a quite a bit of fumes. More than 99% of the cannons out here can take, short of some hybrids. Yeah, it would be cheaper to get your fuel from a source like this, and with fuels other than gasoline it would be even easier. Fuels like alcohol, and ethanol will convert to gaseous form with little effort. I am unsure as to how each would compare to the rest for power, combustion rate, etc. But 5 oz of anything will create a good bit of fuel. You can test this by putting a 1/4 cup of gas in a gas can and set it in your car trunk. Come back the next day and your whole car reeks of gasoline, and there is still liquid fuel in the gas can.

I have seen truck tanks that have been parked in the sun for a weekend and they have almost totally converted to gaseous and read 250 degrees farenheit. Pretty impressive. Large tanks, yes, 3/8 inch thick steel machine welded, also yes. You don't want anything PVC at those pressures or temps, granted it would be extremely difficult getting there. But steel does not build static at anywhere near the ease that PVC does, either. Nor do they fail in the same way. The weakest part of the PVC is the open pipe. The weakest part of steel is the welds and the fixtures.

I know it is a concept. And it actually is a simple to build and useful idea. I applaud you in your thinking and planning. However, sometimes safety has to step in as a major factor. We make guns out of plumbing supplies. We are not necessarily safety minded. But we know better than to test some limits. I just feel this is one limit we should stay away from. Buying the fuel in gaseous form is cheaper than getting skin grafts, and a lot less painful.
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Unread postAuthor: DYI » Thu Oct 18, 2007 4:49 pm

I still don't believe that gasoline can create the pressure necessary to rupture pressure rated SCH 40 PVC. If it could, why would we be using propane, which will only reach about 100 psi combusting at atmospheric pressure?

I understand the concerns about large amounts of gasoline. If it gets exposed to a continuous air source and is ignited, it can create massive, quickly burning fires that resemble explosions closely and can cause extreme damage to anything near them. They can give off large multiples of their volume in gases, which is why the fires can be so violent and long lasting.

Although gas is dangerous to work with, in these quantities I don't think that there is much of a threat to the safety of the operator.
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Unread postAuthor: BigGrib » Thu Oct 18, 2007 5:08 pm

Me personally dont like the thought of gasoline used in pvc or abs guns so i might be a bit biased, i just dont think it's a good idea just due to the charachteristics of gas, especially if you have o rings in there after a bit will get eaten away and leak. anyway just my thoughts.
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