SpudFiles

Ok, so I'm building my first launcher and I have a couple general ideas and questions.
I'm planning on making a simple air or Co2 powerd one for my first, just to get how things work.

I saw some plans on a website linked from here (http://captainnapalm.com/pgcomp.shtml) and I was thinking of doing something like that, only smaller and I wanted to do it in-line without the curve.

I made a little diagram of what I was thinking of doing which can be seen here: http://img343.imageshack.us/my.php?image=spudgun0om.jpg
The sizes are just estimated, not what I've decided on yet. Especially for the C:B Ratio.

As for questions, I don't need alot of power (I don't really need more than 1,000 ft.), so would a .5:1 ratio be good if I'm using air or Co2?
If I hook up a tire pumping valve to it (for use with a powerd air pump), would it be safe to hook up a bike pump that you can use with 12 gram Co2 cartridges through if I wanted to try using Co2 or would it be a better idea to hook up a Co2 quick changer to it?

Thanks

-Random

A .5:1 ratio will be fine, although the GGDT indicates that at 100 psi, you may acctualy want to make the barrel a bit longer at expense of chamber - 6-8" longer, acctually. This would make the ratio more like .3:1. (the heavier the projectile, or the faster you can turn the valve, the shorter the barrel it wants.) However, 100 grams is a fairly good weight for this launcher, and 1/10th of a second is appropreit for valve opening.

Muzzle velocity is about 230 feet/sec, not really dependent on mass. Range, assuming a CD of your projectile (CD has to do with drag) is that of a sphere, will be about 750 feet.

Thanks for the help.

There was something else that I forgot to ask.
If the chamber is the same diameter as the barrel (1 ft. long, 2 in. diameter) but longer, will it react differently than if the chamber were shorter but wider(6 in. long, 4 in. diameter)?

Not very much, if the volume is the same.
A larger diameter alows you to have a larger chamber volume for certain chamber length, however. This in turn gives you more power, and means that you want an even shorter chamber... download the GGDT to learn more. It's a powerfull tool.

That's a great program!

Thanks again.

nah maybe go with a bigger barrel for distance and more narrow for accuar acy to do some destruction

There havn't been any tests on the relitive accuracy of longer barrels... but with a ball valve, it's not likely to matter. He'll be jerking the gun all around when he fires anyway.

Not true, BLB. I can hold my ball valve gun, and I almost always hit the target when I open the valve. It all depends, on the size of the gun, and how good your grasp is.

And the target is how big?

*does calculation for calculation's sake*
ah... 10 degrees per 1/10th second... barrel dwell time = 1/50th second... 2 degree deviation... 12" at 30 feet.

Maybe your definiton is different, but 12" at 30 feet counts as "all over the place" in my book.

The main reason to build this is just that it's my first gun.
I don't really care about accuracy as long as it fires consitenty and doesn't blow up in my hands or fail miserably.

Ofcourse, I won't be dissapointment if it hits soemthing.

lol thats the spirt just blow up something muhahahahaha