Question about the propane bottles

[VirusX]

Hey,

I very often see little propane bottles attached to combustion cannons and I got 2 questions:

1) Where do you get those? Can I buy them in a buildings center or just in special shops?

2) Can I refill those propane bottles by myself or can only experts do this? (and what does the refill cost?)

The days get longer and warmer - Soon it's time to getting started with my combustion cannons. Damn I'm really looking forward springtime

[Jack_Hogg]

To refill Here you go.

You can get them at campming stores, local hardware stores and some other do-it-yourself shops. Just ask around. That's the most effective method I always use.

Do you know exactly what parts you need to build your combustion?

[VirusX]

To refill Here you go.

You can get them at campming stores, local hardware stores and some other do-it-yourself shops. Just ask around. That's the most effective method I always use.

Do you know exactly what parts you need to build your combustion?

Hi, thanks for the information!

so I do have to buy a big propane bottle to refill the little one?

Yes I know which parts I have to use, I already built one combustion cannon and one mini cannon. The combustion cannon had a cap to fill in the deodorant or hair spray.

This time I want to build one with "professional" gase injection

[jimmy101]

If you are talking about using a Bernzomatic type cylinder to fuel a standard sized combustion gun then refilling the cylinder really doesn't make much sense. A standard bottle will give you many hundreds of shots and costs less than $5. It really is not worth the hassle of trying to refill. By the time you buy a larger cylinder and all the fittings and hoses etc. you would have to fire the gun a zillion times to come anywhere near justifying the additional cost.

A standard Bernzomatic cylinder is 14.1 oz (400g) of propane. At room temp and pressure that's about 200 liters (50 gallons) of propane gas. A typical sized gun uses less than 0.1 liter of fuel per shot. So that cylinder is good for more than 2000 shots.

[iknowmy3tables]

yeah the tall skinny ones you usual see that fit inside 3" pvc are used for propane blowtorches which typically are used for sodering copper pipe so you'll find them at the hardware store.

you'll also see shorter fatter ones that fit in 4" pipe which don't fit in the hand as well because they're used for camping stoves obviously they're sold in camping and sporting goods stores.

and their interchange-able

and if you what to know how to mount one on your's check burnt lake which is pretty much the standard resource for that info

[Gippeto]

Some interesting reading on "non-refillable" cylinders.

Not worth doing IMO.

http://www.gizmology.net/dot39.htm

[Marffy]

If you're talking about the green propane tanks, you can buy them at any hardware store pretty much. I believe they would be cheap to refill too. if it were me i would buy a half-dozen green propane tanks and refill them when they are all out of propane. or, buy a couple propane tanks and get one big propane tank and refill the little tanks with the big tank. i hope my input helps.

[McCoytheGreater]

If you're talking about the green propane tanks, you can buy them at any hardware store pretty much.

Hardware store, Wal-Mart, Lowes, Home Depot...etc.

[jimmy101]

If you're talking about the green propane tanks, you can buy them at any hardware store pretty much. I believe they would be cheap to refill too. if it were me i would buy a half-dozen green propane tanks and refill them when they are all out of propane. or, buy a couple propane tanks and get one big propane tank and refill the little tanks with the big tank. i hope my input helps.

Why in the world would you do that?

Besides, it won't work like you think it will. You can't just connect a large reservoir to an empty cylinder. All that'll do is pressurize the empty cylinder with gaseous propane. To transfer liquid is more complex and is really a pretty silly thing to try to do.

Why in the world try to save money on fuel when the fuel cost per shot is already a lot less then a penny? Your ammo cost is going to be more than 100x that per shot.

[Marffy]

If you're talking about the green propane tanks, you can buy them at any hardware store pretty much. I believe they would be cheap to refill too. if it were me i would buy a half-dozen green propane tanks and refill them when they are all out of propane. or, buy a couple propane tanks and get one big propane tank and refill the little tanks with the big tank. i hope my input helps.

Why in the world would you do that?

Besides, it won't work like you think it will. You can't just connect a large reservoir to an empty cylinder. All that'll do is pressurize the empty cylinder with gaseous propane. To transfer liquid is more complex and is really a pretty silly thing to try to do.

Why in the world try to save money on fuel when the fuel cost per shot is already a lot less then a penny? Your ammo cost is going to be more than 100x that per shot.

i didnt know it was hard to refill propane cylinders. i cant buy them so i wouldnt know.

[VirusX]

Hey,

Thanks for all your input! But I can't image the size of the bottles by their volume of gas.

I thought about a propane bottle with a size like this one has: http://www.spudfiles.com/forums/my-rr6-t19769.html

How much propane fits in such a bottle and is it refillable?

(Sorry for my bad english, I'm not from an english speaking country.)

[mark.f]

That is actually butane gas, which I would not recommend using due to it's low vapor pressure. What area of the world do you live in?

Also, it would be far easier to judge how much gas is in the cylinder by measuring the mass of its contents. Weigh and empty container and then weigh a full container. Subtract the weight of the empty cylinder and you have the weight of the contents.

Then, use the molar mass of the gas to measure the contents in moles, which then can be drawn out into a volume of gas at STP.

[jimmy101]

It looks like the large size butane refill cartridge. Butane lighter refills usually come in 100mL and 300mL sizes. The one in the link looks like it is 300mL.

The density of liquid butane is about 0.6g/mL so 300mL is 180g butane. That's 3.1mol of butane (MW=58 ) and 70L gas at STP. The fueling ratio for butane in air is about 3.2% so that cartridge gives about 2100L (540 gallons) of combustion mix.

Figure typical combustion chamber of about 1.6L (100 cubic inch) means that cartridge is good for about 1400 shots. Probably costs $2 for the butane cartridge so the cost per shot for the butane is much less than a penny.

Butane works OK down to about 32F (0C) though the catridge's pressure will be pretty low when it is that cold and that may mess up the metering system. At more normal temperatures of say above 60F (16C) butane is fine. (A syringe meter will work down to 32F without any problems.)

EDIT: Fixed the stupid smiley

[VirusX]

Hey, sorry for my late answer, I didn't have much time last days...

So, he used such a butane bottle to refill normal lighters? http://www.pitopia.de/pictures/standard ... 424821.jpg

How can I connect the nozzle of the bottle with the chamber and still use it? (I still have to press the nozzle down for getting butane).

Some months ago I tried something similar with a hose, the butane got fluid and the hose freezed.

[jimmy101]

If you are properly fueling a typical combustion spud gun you are not transferring enough butane (or propane) to freeze anything.

If your hose is freezing you are using way too much fuel.

IIRC, those butane lighter refills will deliver liquid when upside down and gas when right side up. If your fuel meter system is setup correctly it won't matter if the canister is delivering liquid or gas.