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Last edited by Goody454 on Mon Jul 27, 2009 9:09 pm, edited 1 time in total.
Are you sure you want to make a combustion because you could make a pneumatic which would be bettter for smaller projectiles
C:B refers to the chamber to barrel ratio, meaning an 0.8:1 ratio gives you a chamber volume that is 80% that of your barrel.
If you're using the pipe sizes describes, assuming you have an inline configuration (barrel attached inline with chamber as opposed to inside it) this means you want around 9-10 inches of barrel for every inch of chamber.
It is actually chamber to barrel ratio. It is simply a ratio comparing the volumes of your chamber and barrel. An optimal chamber to barrel ratio, or "C:B", is around .7:1.
To go with metered propane, check out this and this.
Also, are you set on building a combustion? I started out building a pneumatic cannon, but it all depends on if you have an air compressor, or a bike pump.
Edit: Damn, Jack beat me to it.
hmm, where to start.
i would recommend a compression union for breech laoding. if you intend to only launch potatoes the go with the 1.5'' barrel, i find that few spuds fit tightly in 2''.
yo make a grip, take a 1'' tee, cut it in half and attach a 90 degree elbow and about 6 inches of pipe and put the bbq ignitor in there and just use hose clamps to attach it to the chamber, dont even try to glue it.
do you really need a 6'' chamber? that is really expencive and over all uneffective. use 4'' pipe instead.
look into a chamber fan, it will make you cannon unbeliavably more powerful.
a C:B, or chamber to barrel, ratio is the amount of volume in the pipes. most people say that 7:1 is "ideal". this is true if you want it to be fairly quit. i personally like about a 9:1 because it is louder and much more impressive when you are showing it off mainly because you can hear a much louder bang.
to figure out the C:B of your cannon, just find the volume of the barrel and the volume of the chamber and compare the two.
if you need help you can PM me.
edit- damn, jack and modderX beat me.
Last edited by hi on Tue Jun 26, 2007 10:52 pm, edited 2 times in total.
"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote
you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
er, first, your link dosen't work.
The Chamber to barel ratio is the ratio of volume in you chamber to your barrels volume. like a 2:1 ratio cannon (this is just an example, don't use this ratio) would have a chamber 2x the volume of its barrel. A good ratio for most cannons is 1.5 to one. Use the search button on how to measure this and calculate it.
Be shure that your bbq sparker is a good brand, some brands need to be replaced every 25 "clicks" or so, But I recommend a Lantern lighter, the flint kind. You can get them from Ace hardware stores and the website.
I've only just drawn up my plans for a spudgun and most of this info can be found throughout the forum.
Again, use the search feature. It's helped me alot.
My links work fine for me..
Also, an optimal C:B ratio would be <1:1 such as Jack's suggestion of .8:1 or mine of .7:1
Last edited by Goody454 on Mon Jul 27, 2009 9:10 pm, edited 1 time in total.
Mate theres only a few simple things you really need on a decent combustion; a fan, a decent sparker and some proper fueling and measurements. And possibly pvc cementing and all that too but anyway Take it in stages and calculate a decent c:b ratio, buy some decent pipes and a mini-gun styled handles rock
Raise your horns if you love metal.
Welcome to the forums, combustion is mostly out of my territory, i live in suburbia and the nieghbors complain about loud noises. not that i car but my parents seem to. but id like to pass on some knowledge.
I agree with Modder and jack <1:1 C:B ratio would be considered ideal. also if your gonna do breech loading lookup the pass through or through barre design. instead of a BBQ ignitor consider maing an ignitor out of a used disposable camera flash circuit, there is a thread around here somewhere. search for 'flash circuit igntion'. your local walmart photo center usuall gives them out if you say your looking for one for a science project. and the rest of the parts are usually cheap/free depending on what you already have. Also like Hi said look into a chamber fan.
And you should go with a propane metering system, propane will give you much better results than aerosols.
If you need anymor help you can also feel free to PM me.
FAN FAN FAN FAN FAN!!!!!!!
The better those gases are mixed the more bang for your buck you get- probly like an extra 33% No B.S.
http://www.angelfire.com/80s/sixmhz/camera.html camera ignition plans
I will second, or, maybe eighth the motion that you include a fan, flash circuit, and propane meter, and the volume of your chamber should be approximately .8 that of your barrel.
"Who ever said the pen was mightier than the sword, obviously, never encountered automatic weapons."
-General Douglass MacArthur
Read my dog's blog - Life of Kilo
Camera flash igniters suck. They require multiple seconds of charge time between attempts to fire, require a very small spark gap, and are prone to electrode erosion problems. You can dump the charge through an ignition coil, but this setup is large, bulky, and highly dangerous.
A BBQ igniter on the other hand, can be salvaged from an old grill for free, and will provide up to a 1/2" spark. Out of the 20+ igniters my friends and I have been in possession of, only one has failed. It also happened to be the only one that was purchased new.
People should not be afraid of their governments. Governments should be afraid of their people.
Goody welcome to the forum...
Research pneumatic well. It cost a bit more in parts then a basic combustion.
Kenny thanks for the link...i havent tried \a camera flash yet..
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