Need a little help

[Andrew52]

hey guys im going camping and a bunch of the older guys have some regualr run-of-the-mill abs spudguns and i have one to but i have been planning on biulding a nice one propane injection chamber fan but not stun gun not enought time (im leaving in four days) and i have some fittings but i have money again so i can but more stuff but i was wondering how long would be a good size chamber for 1.5" barrel 4"chamber and i looked on burnt latke for propane injection and i dont really know a good method for measuring my chmbaer unless you guys know for say 12" is so may ci and i dont get the last part for putting pressure into the equation. but fore the most if you had a 100ci chamber you meter should hold 4ci sory if its confusing
oh and just so you know im not a nube at this but i just need a little help on some stuff

[SpudStuff]

use the fuel tool on http://www.Burntlatke.com

[Andrew52]

thanks is a 1.66 ratio good for a propane injected combustion

[sgort87]

1.66:1? No. I mean, it will work fine, but your best power will come from a .6:1 C:B ratio.

[CS]

Gort do you mean to say most efficient or power over overall space? Lets imagine some cannons in our hea... For the first cannon we will leave the chamber at a fixed volume of 60ci. So which will shoot farther; a barrel with a volume of 60ci or 100ci? Obviously the 100ci seeing as the force from combustion has a longer period to exert force while not slowing muzzle velocity due to friction.

Now lets leave the barrel volume at a fixed volume of 100ci. Which will result in a farther shot; a 100ci or 60ci chamber? 100, although this is not in sync with the suggested .6:1 ratio. Basically if the barrel volume is left at a constant only increasing chamber volume will result in more power.

Ratios should be simply kept in mind seeing as a top heavy ratio might be less efficient, but are objective isn’t efficiency, rather power. Hopefully you "feel" what im saying. Basically seeing as far as post cannon construction we are not bound to either a fixed chamber or barrel volume, the ratio should only be kept in mind.

[Andrew52]

ok its time for an update i have most of my parts i have 2 ft of sch 40 4" and i have a 6 inch lenght of 3/8" pipe it one of thos brass ones or something and what would be a good length so i dont have to buy a regulator becuase there exspenisive

[sgort87]

Actually Tony, there is a limit. Remember my Bolt Action Golf Ball Barrel? Well I tried it on two different launchers of drastic size differences. One chamber was 1' of 4" pipe, the other (The Effin' Launcher) was 4' of 4" pipe. The 1' chamber consistently put golf balls through 3/4" plywood while the other merely caused the balls to bounce off. What hjappens is it doesn't reach the peak before the projectile is out.

[CS]

Hmmm, very intresting Gort. I would never had guessed that. Although, im struggling to comprehend with my simple logic mind how bigger can be less. (although feasible as somethings seem to dodge and counter simple logic)

Although, remeber "Basically seeing as far as post cannon construction we are not bound to either a fixed chamber or barrel volume, the ratio should only be kept in mind." ?
*laughs to self*

[sgort87]

I think your "simple mind" has tricked you into thinking you are onto something.

The ratio is what I'm talking about here. The launcher significantly loses power with anything less than .5:1 and anything greater than 1.2:1. Roughly, The ratios were 1.1:1 and 4.3:1.

Like I said, the peak pressure is not hit before the projectile is already gone in a large ratio launcher.