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Need Help - First Cannon

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Need Help - First Cannon

Unread postAuthor: tsb » Mon Oct 08, 2007 9:06 pm

Hey, i recently made my first cannon, it was 134cm long, and i first tried some hairspray, it got around 4 meters, i then tried some deodorant, it didn't even fire, i then tried some butane propane mixed gas, and i got it over my fence, so it was around 22 meters, but i had seen some really good cannons and my sis said her friends one got over 100hm so i cut down the barrel so it was small to try and focus the blast in the area where the spud was (btw im using a BBQ lighter) but i can still only get it over my fence, im holding the butane propane gas in for around 15 seconds, can someone give me plans for a simple spud gun or tell me how to improve mine and tell me what fuel i should use..

Thanks in advance

PS: Check second page, need answer!
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Last edited by tsb on Thu Oct 11, 2007 2:45 am, edited 2 times in total.
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Unread postAuthor: Novacastrian » Mon Oct 08, 2007 9:18 pm

You are probly using too much fuel, and your barrel is most definantly too short, aim for a c:b ratio (chamber to barrel) of around 1:1. So if your chamber is 1litre make your barrel 1litre too.
There is heaps of info if you use the search feature kindly provided by Spudfiles (You WILL get flamed if you don't bother to search)
You should aim for a fuel ratio of approx 4% propellant to air (4% fuel 96% air)

Welcome to Spudfiles :D Now go searchy :lol:

P.S. Pics would help us help you even better.
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Unread postAuthor: tsb » Mon Oct 08, 2007 10:04 pm

Hey nova, you said about the C:B ratio, well i held my propane ( I used straight propane this time) for around 5 seconds, and it went at least 100 m and my combustion chamber is 1 litre and the barrel is the same length 33 cm roughly and its alot smaller in diamter so it isnt 1 litre but it still went 100m..

Well i was using to much fuel so thanks for your help :D
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Unread postAuthor: Novacastrian » Tue Oct 09, 2007 9:42 pm

Glad to be of assistance :) Now stuff a longer barrel into that chamber!
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Unread postAuthor: tsb » Wed Oct 10, 2007 1:40 am

I did, now its about 1:1 ratio and i cant get it to go very far, i got it round 100m once and now i can only get to my back fence

Any ideas?

Thanks
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Unread postAuthor: jimmy101 » Wed Oct 10, 2007 12:07 pm

If you CB really is ~1:1 then check;

Too much or too little fuel. You really need to get to 4% +/- perhaps 0.5% to get good performance.

Gases don't mix very well by themselves. Install a chamber fan or invert the gun slowly several times after fueling to give the propane a chance to mix thouroughly with the air.

Make sure you air the chamber out well between shots.

You're firing tight fitting spuds? Any blow-by (gas excaping around the ammo) will drop the performance of the gun. A barrel knife (aka spud cutter) will gaurantee that you have tight fitting, air tight spuds.
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Unread postAuthor: mtronic » Wed Oct 10, 2007 5:14 pm

If its possible post a few pics, because "my cannon is 134 cm long" isnt very helpful if you do post them the guys/girl here will be able to tell you everything you need to know.

From what I've read you may be over fueling it, especially with the butane. I use a 1 second to two second spray(starter fluid-experiment with your fuels) and then mix it with the fan and get over 200m. Also try not to spray the fuel directly onto the electrodes and remember that it the fuel vapour that you want, not liquified fuel on chamber walls.

hope that helps, if not pm me and i'll help some more and search around too :)
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Unread postAuthor: tsb » Wed Oct 10, 2007 6:14 pm

Ok, just so you guys know, this is the specs of my cannon:

1. A 32mm x 94cm sch 40 PVC barrel (just under 1 litre)
2. A 90mm x 33 cm sch 40 PVC combustion chamber (1 litre)
3. I use just a BBQ lighter, I havn't found ANY lantern lighters in australia and the ones of ebay only ship to the USA :(.. And stun guns a illegal, and i do not have a clue about those spark strips and what not.
4. A messy glue job

I spray in exactly 3 seconds of LPG gas and it goes around 125 M..

I have filed the barrels end so its sharp, so the potatoes fit...
And i have used the search function and i havnt been able to find out how to install a fan, i also had a quick look on the wiki.
Can some one give me a link to a tutorial on how to install a chamber fan?

Thanks in advance, TSB
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Unread postAuthor: miskaman » Wed Oct 10, 2007 9:02 pm

Click

Try that.
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Unread postAuthor: tsb » Wed Oct 10, 2007 9:55 pm

Thanks miskaman, my dads going to go pick up a fan today from my Pa's house (he recently died from cancer) and we will hook it up tonight.
Kudos


TBS
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Unread postAuthor: Thegoodlife8806 » Wed Oct 10, 2007 11:22 pm

Acytiline is a wonderful propellant, that is, if you trust it. As long as all your connections on the cannon are glued properly, you should not have a problem. It can be picked up at any hardware store in the Bernz O Matic canisters. MethylAcytiline is what is printed on the bottle, which is yellow. You can also pick up a small tank of it at any welding supply store. Its relatively cheap, but most important, dangerous if misused. I also tend to get good results from WD-40, when held upside down and shaken. I achieved around 200m with that method. Starting fluid is another good one.

Good Luck on your ventures.
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Unread postAuthor: Pete Zaria » Thu Oct 11, 2007 12:02 am

Thegoodlife8806 wrote:Acytiline is a wonderful propellant, that is, if you trust it. As long as all your connections on the cannon are glued properly, you should not have a problem. It can be picked up at any hardware store in the Bernz O Matic canisters. MethylAcytiline is what is printed on the bottle, which is yellow. You can also pick up a small tank of it at any welding supply store. Its relatively cheap, but most important, dangerous if misused. I also tend to get good results from WD-40, when held upside down and shaken. I achieved around 200m with that method. Starting fluid is another good one.

Good Luck on your ventures.


I'm sorry, but you, sir, have absolutely NO CLUE what you're talking about, and you should NOT be giving advice to people.

The yellow canisters at hardware stores are MAPP gas, which is a mixture of propane and methylacetylene-propadiene, NOT ACETYLENE.
http://en.wikipedia.org/wiki/MAPP_gas
These are the Benzomatic cylinders you're talking about: http://www.mclendons.com/img/products/04/045120.jpg

MAPP gas is liquefied above a certian pressure (just like propane), making it safe to store pressurized in metal canisters like that.
Acetylene must be dissolved in a chemical such as acetone to be stored safely, and if compressed in gaseous form will self-ignite around 30psi. I've also never heard of a hardware store anywhere that sells acetylene, AFAIK you can only get it from welding supply stores/companies.

MAPP gas, when combusted, produces a deflagration - this is very good for spudguns.
Acetylene, when combusted, produces a detonation - this is how we get PVC fragments in our skulls and die.

Acetylene should only ever be used in metal chambers, in my opinion. There have been reports of people burning it in plastic pipe, but it's russian roulette if you ask me.

Sorry to be an asshole. But please don't give advice unless you know what you're talking about.

Peace,
Pete Zaria.
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Unread postAuthor: tsb » Thu Oct 11, 2007 12:54 am

Well my first cannon is coming along now.. Im just about to go down and install a chamber fan ( I got a few from my Pa's house, he recently died of cancer wich was a shock because no one had told me he had cancer...)

And iv been putting around 3 seconds of gas in each time, wich has been getting the spud around 100-150m, normally around 125m.

And one more question; i have a blow torch that is filled with LPG gas, can i insert it so the gas passes through the fan, because with the fan there isnt enough room for the end of the blow torch past the fan..

Thanks in Advance
TSB


EDIT:Good news! I have installed my chamber fan, and i made a switch because i couldnt find one. ( I know iv got one somewhere )
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Last edited by tsb on Thu Oct 11, 2007 1:25 am, edited 2 times in total.
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Unread postAuthor: Novacastrian » Thu Oct 11, 2007 1:05 am

Hey tsb, sorry to hear of your loss.
A fan is used for two things, to vent exhuast gases and also to mix the fuel with the air prior to firing ( you can get about 30% more power with a fan).
What you are talking about doing is injecting fuel without knowing how much you are injecting (spray and pray). There are fuel meters that can be made so you get the perfect amount of gas each time, research fuel meter before you stick that blowtorch nozzle inside your gun.

BTW, You had a problem with the end cap flying off, did you not?
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Unread postAuthor: ammosmoke » Thu Oct 11, 2007 1:10 am

Man, that really sucks that he died... I am sorry to hear that. You should always tell somebody you are sick....

@Pete
Hey, you shop at McClendons too? They are the best aren't they!
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