PVC Pipe Gasoline Resistance Test

Post questions and info about safe and unsafe materials that can be or should not be used to construct a launcher. Also post things about different universal accessories for your cannon (breech loader, muzzle break, etc.)

Postby benstern » Mon Jul 11, 2005 8:57 pm

The experiment was not conducted properly!

*There was only one trial conducted
Solution: Try to do 3 to 5 trials list all results and give an average
*Experiment did not take into account all variables
Solution: Consider using more variables Such as:
1)Scrubbing inside of pvc pipe with an abrasive to simulate normal wear and tear
2)Not all manufactures put the same chemicals in their pipe. Use pipe from various manufacturers.

I might list more problems as I think of them.
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Postby plasticex009 » Mon Jul 11, 2005 11:18 pm

Benstern, that is a pretty bold claim, but I am positive that if repeated the results will agree with the above information: PVC piping is highly resistant to gasoline chemical attack.

Conducting more than one trial would be excessive because the effects would have been the same. The pipe dimensions were used to illustrate that one pipe specimen had changed while the others had not. These dimensions will vary slightly, but they are not useful enough in this test to need to have exact measurements.

Scrubbing the pipe would not help this experiment because the pipe wasn't coated with anything that would resist solvent penetration. The sections were washed with warm soapy water before soaking to remove dirt and oils.

Manufacturers are required to use very similar plastic compositions for their pipes (it is called standardizing), so it makes sense that these plastics would have nearly identical chemical properties.
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Postby BewareOfDog » Tue Jul 12, 2005 12:33 am

And here I was almost ready to test-fire my first gasoline-powered combustion launcher!
benstern has saved my life, and is my hero!:):)

plasticex009, I'm suprised that this got a rise out of you. Tonight, I spent most of my time
finding links to supposedly non-existent <b>CLEAR PVC Primer and Cement, LOWE'S air pressure regulators</b> and complaining about people using GGDT to design cannons to launch magical elf-manufactured ammunition.

It's more sad than comical, because you would like to give everyone the benefit of the doubt and "assume" that they are not completely [intercourse]ing stupid. So it makes you wonder if they are just doing this to get a rise out of you, because they <b>have</b> in fact, succeeded!:evil:
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Postby BigBang » Mon Nov 28, 2005 3:28 pm

Hey Gang,

I found this thread recently. I hope this post is relevant.

I have been thinking of writing a fueling calculator for gasoline. I abandoned the project when I calculated that the peak pressures expected were essentially the same as for propane and MAPP. Here's the math...

The combustion reaction for isooctane (a common constituent of gasoline, and the most common simple model) in air is:

C8H18 + 12.5(O2 + 3.76N2) --> 8CO2 + 9H2O + 12.5(3.76)N2

Therefore the number of reactant moles is nr=60.5, and the number of product moles is np=64.0.

The best estimate of the adiabatic flame temperature for isooctane in air that I could find was 2275 degrees Kelvin.

Therefore, the peak pressure expected for a stoichiometric mix of isooctane in room temperature air is...

Pmax = (np/nr)(2275/298)(14.7) = 118.7psia = 104.01psig.

A similar calculation for propane yields a peak expected pressure of about 102psig. For MAPP gas, the result is about 104psig. Since there seems to be no performance benefit, and only a few handling hassles in using gasoline, I abandoned my project.

Does this jive with any of your observations?

Comments? Suggestons?

I hope you had a good Thanksgiving,
BigBang
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Postby BewareOfDog » Mon Nov 28, 2005 5:52 pm

A long while ago, I pissed off D_Halls with my unwarranted comments towards a GGDT version for Combustion Launchers.

If you have the ability, I would much rather see a version of this, then a fueling calculator. It would be really nice to test your data with a launcher. It would/could help me decide whether or not a 6" Chambered/ 6" barreled Combustion Launcher is more powerful than a dual 3" valved pneumatic.

Or, if a 2.5" barreled combustion is more powerful than a 1" valved pneumatic, etc.

BUt, a fueling calcuulator would kick butt as well . Liquid hydrocarbons, are messy and dangerous to use though?
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Postby BigBang » Tue Nov 29, 2005 10:46 am

Yeah, I remember the discussion of a combustion model for GGDT. I hope D_Hall will resume that project sometime. I never had much interest in pneumatics till I started goofing around with GGDT. I still prefer combustion guns since they are more fun (IMHO), so the idea of a GGDT for combustion guns got me really excited. Maybe D_Hall will resume this project as a Christmas present for us????????????

All the calculations I've done have been for peak pressures only (for safety considerations), and not overall performance. The rise of pressure as the reaction takes place, and the drop as the projectile moves down the barrel are not factors I have the skills to track. Of course, the geometry of the chamber is a factor too (I found your thread a while back on using the restrictor plate and funnel tip very interesting. I even saved a few Progresso soup cans to make one myself someday.)

BTW, the hybrid I keep threatening to build is mostly finished out in the garage. It is double walled 3" SCH 80, with a 5' golfball barrel (SDR-21 sleaved into 2" SCH80). The chamber volume is 2000ml. I'm now working on new fueling system I call "fuel pods." I'll post more on that when I'm done. The only thing holding me back on this project is that I have absolutely no place to shoot a hybrid - and so I keep getting distracted with other things, like figuring out whether or not gasoline is a worthwhile fuel.

Sorry for the kind of off topic post.

HoHoHo,
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Postby aturner » Tue Nov 29, 2005 11:46 am

Hi BigBang.
I avoid gasoline due to the handling issues. It's messy. I tend to get it on my hands even when refilling my lawn mower. And the vapors/odors from gas linger for what seems to be "forever".

But I mostly worry about ignition of excess airborne gasoline vapors....

On one extreme, I've read in the paper about someone using gasoline to saturate wood prior to starting a large bonfire, and the vapors in the air ignited and led to significant injuries for people who thought they were standing a safe distance away when the fire was first lit. I recall that the injured individuals were thought to have inhaled airborne gas vapors before the fire was lit, and the most severe injuries to these people were from the burning of these vapors inside their lungs.

I've personally used gasoline to burn out yellow jacket nests in my yard. For folks unfamiliar with yellow jackets, they are an agressive type of bee that create their hives in the ground. When I've torched the nests, I've poured a cup of gas down the main hole, retreated a good distance to light up my torch on the end of an extension pole, and then touched off the gas in the hole. I often see jets of flames from the hole which run along small valleys in the surrounding ground (thus my use of an extension pole to light), which I think must be excess gas vapors drifting and pooling in these low areas.

For spudguns, I think I would mostly worry about people spraying gas into a chamber with a cheap spray bottle--it might be safe for a while, but eventually someone stands a decent chance of getting burned. Maybe a little excess gas on someone's hand or a flannel shirt sleeve, then as the person holds the launcher they accidentally place their hand near an exposed electrode on the launcher, and with a clikc of the ignitor there is a spark and the burn begins.

Now, if a non-messy way to use gasoline in a spudgun can be devised, then that would improve safety. Maybe something like a carbuerator jet combined with a small hand pump can be used to meter gasoline with no direct human contact? It might be a fun challenge to build, but I don't see it as a mainstream way to power spudguns.

Finally non-related comments. I can't wait to see your hybrid BigBang, especially now that you've teased us with mention of a unique fueling system. As for the combustion model Hall was working on, I agree that it would be great to see it happen some day. I think most of the strife was caused by folks (like me) who argued with Hall about fueling proceedures for hybrids. This is unfortunate b/c in reality very few people have hybrids, but a lot of people could make use of a standard combustion modeling program. If Hall reads this and is inclined to re-start, I can try to produce data to validate the model.
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Postby Atlantis » Wed Jun 21, 2006 1:25 pm

Do you know of any chemicals that would slowly eat the walls of the pipe? I'm wondering if their is a chemical way to bore a 1.5" barrel a little bigger for golf balls. Could I put primer or cleaner on a rag and run it through the pipe?
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