Monsters of the Potato Gun World (video update 2/3/08)

[rcman50166]

Now The Most Replied Combustion Cannon On The Site



Hehe I'm a new member but would it be too much too ask for some feedback on my cannons? There kind big. "Go big or go home" as they say.


STATISTICS

THE "SARGE"
The barrel on the "Sarge" is 1.5 in. in diameter and the length is 5 ft. The chamber on the "Sarge" is 4 in. in diameter and about 4 in. short of 5 ft. in length. I'm thinking about using a dual gap on it in the near future.

THE OLD "GENERAL"
The "General" is a monster with two 4in. chambers at 3 ft in length with a spark gap in each chamber. The barrel on the "General" is a whopping 3 in. in diameter and about 5 ft. in length. The "General" is a variant of the cannon designed for the U.S. Department of Agriculture on Spudtech.com. It Uses a power limiter valve (that i don't often use). There is a 7-8ft distance between the sparker and the cannon itself when firing.

THE NEW "GENERAL"
The monster of Connecticut has grown even more! In it's development it has grown a 10ft barrel, 4 new spark gaps for a total of 6, 2 new chamber fans, and an ignition coil firing system.


POWER
The mathematics were done using the video recorded for youtube and it is estimated that the "Sarge" has a muzzle velocity around 250 ft/s and the "General" has a muzzle velocity of 300 ft/s. Yes, the bigger gun that uses heavier ammo is faster than the smaller one.
EDIT: The "General", since it's overhaul, has an estimated muzzle velocity of 350 ft/s.

FUEL
injected gasoline





[youtube][/youtube]


This is a new video that I didn't know was made. Found it the other day on youtube. This one is unedited and brings the image of the gun into viewable perspective.
[youtube][/youtube]

[Novacastrian]

What do you use for fuel in this monster?

[rcman50166]

wow 5 minutes after i post. Anyway, i use injected gasoline. It always seems to work the best. Even better than hairspray. Get a two dollar spray bottle and fill it with gas. It works the best if the walls are sprayed with gas and then let to run down the sides of the chamber. This increases the surface area in which the fuel has to evaporate. This loading technique doesn't only apply with gas though.

[daberno123]

WOW! you seem to already know a fair bit about spudguns. Welcome to the site and please share your knowledge with others.

Could you post some stats like chamber and barrel size?
They're both well built monsters and i hope to see more from you

[noob of noobs]

Uh...Gasoline? That sounds a bit dangerous. I've never heard of anyone using gasoline before, and I'd assume that's for a reason. Gas propellants are pretty hard to over power since they won't ignite, but liquid gas wouldn't be that hard. Plus you have the fact that gasoline is pretty reactive. Do yourself a favor and switch to propane.

[potatoflinger]

Yeah, I would switch to propane, it's much safer than gasoline, and it will work almost every time (if you build a meter).

[rcman50166]

I would love to switch but those systems are pricey. Especially when I am testing out different variations of width to length ratios and gap design. Basically what I'm saying is these are my experimental cannons and no huge upgrades are neccessary until i know exactly what I'm doing. But I'm appreciative of you're feedback.

[daberno123]

Gasoline is fine to use in reasonable amounts, he said he's only using it in a spray bottle so it should be ok.

But metered propane would be nice on the Sarge but not on the General, its tank size would go through a propane tank quickly.

Heres the link on how to make one


http://www.burntlatke.com/lp.html

and BTW the perfect chamber to barrel ratio is .8 to 1

[rcman50166]

Well thanks. I will use the ratio mentioned. The site you have provided me is very thorough. I may use the same system on future cannons. However these cannons are going to have to stay gasoline injected. I've taken precauctions with the "General" anyway. Notice the blast shield around the chambers in the video and pictures. I have the same basic awareness everyone else has.

[STHORNE]

nice cannon and welcome to spudfiles new member!

beastly looking cannon you got there

[DYI]

Interesting fuel choice. You don't have to worry about overfueling with gasoline, as it doesn't contain its own oxidiser and is thus limited by the levels of oxidiser available in the chamber. The "Sarge" would be more effective with a smaller chamber, and both could benefit from an inline design. However, the most effective (and cost effective) method of increasing a basic combustion's performance is to add a chamber fan, creating turbulence and enhancing burn rate.

And what's the ball valve on the back of the General for? I wouldn't call these things monsters, as they could easily be handheld. The 3" barrel is a rather uncommon feature on combustions, as it makes finding ammunition a bit more difficult. If you can put enough power behind it however, 3" is actually a very good barrel size.

[jrrdw]

Useing "Gasoline" in chambers this size is the same dam thing as playing with a time bomb! It is the fumes that are igniting not the raw liquid. Rule of thumb when dealing with gas fumes -- One gallon of fumes equals one stick of Dynomite! Your chamber size is at least two gallons!
The only reason you haven't been hurt or killed yet is because you haven't gotten unlucky enough to get the rite optamon mixture yet, and hopfully you wont! I also hope no one else is near you when this explodes!

Remember safty first! For the members who posted here all ready -- PULL YOUR HEADS OUT OF YOUR ASSES!

We are sapossed to help members by promoting safty first!

rcman, YOU ARE PLAYING WITH A TIME BOMB! IT IS GOING TO EXPLODE, YOU JUST DON'T NO WHEN OR HOW BADLY.

Have you ever seen a stick of Dynomite go off? I have, turst me you can't build enough protection to keep yourself safe.

Welcome to Spudfiles.

Sorry about the shouting, but some one needed to step up!

Importent Edit: Before anybody else tells me/rcman that I don't know what I'm talking about, please read 1st post of mine carefully!!!

[SpudFarm]

it is not that bad. there isn`t more powerful or reactive when it comes to blow stuff up than MAPP gas in my opinion just get to a safe distance since you are the first to do this we dosen`t know what can happened with that fuel.

[DYI]

@jrrdw: I hate to start a war, but almost everything you said in the above post is dead wrong.

Firstly, he doesn't have a gallon of fumes in there. If he had a gallon of fumes in there, his chamber would probably need to be at least 10 gallons, probably more. A gallon of fumes in a chamber that size wouldn't ignite, as there would be no oxygen to allow combustion.

Secondly, the reason a stick of dynamite is so dangerous is its energy density, along with the fact that it produces a hyper-mach detonation wave. There are several launchers on this site whose chambers contain multiple times the energy that a stick of dynamite does, but, lo and behold, they don't explode. Something with the equivalent energy of a stick of dynamite, but in hundreds of times the volume, with no detonation, isn't particularly dangerous.

Thirdly, the combustion of gasoline produces very similar pressures to the combustion of propane, quite probably less so. So by saying this, you have essentially stated that all propane combustions on this site are time bombs primed to kill us at any second.

Once again, the energy contained means nothing if the volume it is contained in is not taken into account. If his chamber was the size of a stick of dynamite, and contained the same energy, then we would have something to be worried about.

RCman, I would just like to assure you that jrrdw, despite his high post count, has very little knowledge in these matters. His post is based on incorrect information and faulty logic, and is no cause for alarm on your part. Your cannon is no more likely to explode than any other spray'n'pray combustion.

[mark.f]

JRRDW is an automotive tech. Therefore, when he says a gallon of gas fumes has the same amount of energy as a stick of dynamite, he probably means a gallon of gas:air at a 10:1 compression ratio.

One gallon equals ~3.79 liters of volume. At a 10:1 compression ratio, that is ~37.85 liters at atmopsheric pressure. Multiply that by an optimum stoichiometric ratio of 14.7% gas:air, you get ~5.56 liters of gasoline vapours. The ∆H_COMB of gasoline is around 47 MJ/kg. Here is the point we lay this myth to rest.

The ∆H<SUB>COMB</SUB> of propane is 49.9 MJ/kg. Therefore, using the same conditions with propane, you will have more energy than using the same conditions with gasoline. Mole count is constant with constant volume, (neglecting varying temperature), at constant pressure, so 5.56 liters of propane has more energy than 5.56 liters of gasoline vapours. Only thing that may differ is burn rate, and I can reasonably say that most gasoline burns slower than propane, (depending on octane rating and other factors).

Gasoline is no more dangerous than propane. There is no way to add "too much" either, as there will be no more air to combust it with. The only concern for a while was whether or not it degraded PVC or other plastics, but test showed that it did not.