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New fuel meter concept.

Unread postPosted: Wed Oct 03, 2007 10:25 am
Author: Fnord
Alright, I don't know if this has been thought of before, and I don't know if it will work, but I'm posting it anyway.

This is just a simple idea I had the other day. Basically it is a fuel meter for liquid fuels such as gasoline, but you could use practically ANY flammable liquid you can find.

Here's how it works:
The tank is filled with fuel (gasoline), and the plunger is pulled back. The vacuum it creates causes the fuel to boil until gaseous octane fills the cylinder.

The plunger is pushed forward and the octane is injected into the chamber
(Boom).

You'll need to put a sponge or cotton in the tank to keep the fuel from leaking into the meter volume, but that shouldn't be a big deal.


Pros:
-Cheaper fuel. (Fill your gun up at the pump :))
-No propane leaks.
-Almost any fuel can be used, so long as it has a reasonably low boiling point i.e. not cooking oil.
-Possibly cheaper to build.
-No set meter volume.
-Works out your arms!

Cons:
-May require a bit more work to build than propane meters.
-May be affected by altitude/temp.
-Tends to start semi-pointless arguments.

I can't think of anything else negative. I'll add other things if you find any.
Edit: this design is best used on smaller guns. The meter volume would get too big if you tried to use it with a 4"x36" chamber

Unread postPosted: Wed Oct 03, 2007 10:46 am
Author: super spuder
hmm, interesting idea... wonder how effective it would be

Unread postPosted: Thu Oct 04, 2007 12:49 pm
Author: jimmy101
Very nice idea. The meter volume and plunger could be a syringe. This is a nice way to get around the need to measure a few drops of a liquid with sufficient accuracy.

There are a few minor problems. Initially the liquid fuel reservoir will have a mixture of air and evaporated fuel as the gaseous phase. This will mess up your measurement of the gas volume since the syringe will contain a mixture of air and fuel. You might want to cycle the meter a few times to purge the reservoir of air before using it to fuel a gun. (You have to do the same thing with most propane meters.)

You also need to take into account the vapor pressure of the fuel. The gas pressure in the syringe will be whatever the vapor pressure of the fuel is at the ambient temperature. I believe the vapor pressure of gasoline at 100F is about 10 PSI. For other fuels;
Acetone (finger nail polish) 3.9 PSI at 72F
Diethyl ether (ether) 8.7 PSI at 72F
Isopropanol (IPA, rubbing alcohol) 1.2 PSI at 80F
ethanol (grain alcohol) ~1 PSI at 70F
methanol (wood alcohol) ~2.5 at 70F
propane 305 PSI at 131F
water ~0.4 PSI at 70F
(most values from http://www.s-ohe.com/vp_data.html)

All of the math for calculating how much gaseous fuel is actually in the syringe will depend on the pressure of the gas (the fuels vapor pressure) and the temperature.

Unread postPosted: Thu Oct 04, 2007 12:56 pm
Author: Tom
I'f it works make the plunger move lika a pump-action handle :D .
GR.Tom

Unread postPosted: Thu Oct 04, 2007 5:02 pm
Author: silverdooty
i used to work on aircraft fuel systems in the usaf(20+ yrs.). liquid fuels in this type of scenario are dangerous. all you've done is reinvent the molotov cocktail.

if you have any type of material that can create static electricity you will die.
your plunger must not be able to create static.
all of your fittings must be grounded to each.
you should also have some type of nonexplosive foam to take up the space in the fuel cell.
your fuel cell must be able to withstand an accidental explosion.
this whole apparatus should be grounded while firing and you should be grounded to it.
pray to god your check valves work or a spark or flame from your chamber will leave a lasting impression.
drier climates are also more prone to static electricity.

static electricty + liquid fuel = death

Unread postPosted: Thu Oct 04, 2007 5:08 pm
Author: iPaintball
Uhh, hold on there. Small amounts of gasoline + static electricity, most certainly does not mean "death" The spark would have to make contact with the fuell vapor to even catch. Even if it it did somehow cathc on fire, the deflagration would in no way be powerful enough to cause death.

Unread postPosted: Thu Oct 04, 2007 5:31 pm
Author: silverdooty
and what would be the proper amount of static electricity and gasoline to promote death? i do hope your personal experience is more vast than mine.

i've had the mis-pleasure of investigating several static/fuel accidents in my life. the smallest one involved less than a gallon of pump gasoline, 12% humidity and pair of nylon socks. two airmen died from third degree burns to over 95% of their bodies.

Unread postPosted: Thu Oct 04, 2007 6:06 pm
Author: DYI
For this scenario, as long as the fuel cannot escape the metering system, there is no problem if it does ignite, and it won't burn very long inside the meter, as it will use up all available oxygen very quickly.

On the other hand, if he soaks himself with fuel, and then fills the chamber with liquid oxygen and gasoline, well...

I think that you're overeacting here. As long as proper safety precautions are followed, it is a very safe system. Unecessary and complex in most situations, but certainly not deadly.

Unread postPosted: Thu Oct 04, 2007 6:36 pm
Author: silverdooty
yea, i probably overreact. that's what happens to us old guys that use to play around with a lot of this stuff. every thing is safer now. thank god it is all new science and all the old stuff is gone. we're so much safer now.

it is still a molotov cocktail and pvc will still create static electricity.
an ounce of precaution

Unread postPosted: Thu Oct 04, 2007 6:49 pm
Author: sandman
if it does ignite will not the syringe plunger just pop out?

Unread postPosted: Thu Oct 04, 2007 6:53 pm
Author: MikeNice
I'm with silverdooty on this one. Piezo BBQ ignitors work on static and many of us fire our guns with those. I know it sounds corny but remember mom saying "Better safe than sorry." Never doubt the eternal wisdom of mom . . . . or that of a dude with 20+ years experience in fuel systems.

-Nice

Unread postPosted: Thu Oct 04, 2007 7:03 pm
Author: Fnord
If this small amount of pvc/metal/whatever did collect enough static to create a spark AND there was an explosive mixture of gas and air in the tube AND the whole thing was somehow weak enough to break apart when it ignited then yes, you might just get hit with a wad of cotton soaked in gasoline. This would, of course kill you in the most slow and painful way that it is possible to be killed by 3-5 ounces of gasoline.


If I was going to put anything on a cannon that contains a flammable substance I would use parts that can handle the pressures generated.

In short, yes, you are over-reacting.

Unread postPosted: Thu Oct 04, 2007 7:35 pm
Author: spudgunnerwryyyyy
That would be great for propane, but it would work best with ethanol as it needs a accurate way to measure fuel and this isn't as ghetto as just a syringe so i like it. Great job.

Unread postPosted: Thu Oct 18, 2007 10:29 am
Author: psycix
silverdooty wrote:if you have any type of material that can create static electricity you will die.
your plunger must not be able to create static.
all of your fittings must be grounded to each.
you should also have some type of nonexplosive foam to take up the space in the fuel cell.
your fuel cell must be able to withstand an accidental explosion.
this whole apparatus should be grounded while firing and you should be grounded to it.
pray to god your check valves work or a spark or flame from your chamber will leave a lasting impression.
drier climates are also more prone to static electricity.

static electricty + liquid fuel = death


1. 99% of all our spudguns are PVC, and we have never experienced firing because of static sparks. You are stating every PVC pipe with a gas mixture inside is dangerous.

2. If it does ignite, so what? our PVC is PRESSURE RATED, the overpressure will just flow into the chamber through the check valve and the plunger may pop out. You are stating that every PVC pipe that has a combustion insides explodes and causes death.

3. If it does ignite AND explode, it doesnt always cause death.

Your turn. :wink:

Unread postPosted: Thu Oct 18, 2007 11:32 am
Author: silverdooty
do you understand how static electricity works?
do you know what the triboelectric series is?
do you know where pvc is located in the triboelectric series?
do you understand how the plunger comes into play in static electricity?
do you understand why your generic pvc spudgun does not create static electricity?
do you understand words of caution?
do you realize that _fnord posted the 3-5 ounces after all my other posts? big difference after seeing the diagram in the original post.
and did you read all my posts?

the post you missed from dooty wrote:yea, i probably overreact. that's what happens to us old guys that use to play around with a lot of this stuff. every thing is safer now. thank god it is all new science and all the old stuff is gone. we're so much safer now.

it is still a molotov cocktail and pvc will still create static electricity.
an ounce of precaution


neat little trick for ya
in firefox>> highlight text >> right click >> select "Search Google for"