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Unread postPosted: Mon Jul 17, 2006 8:05 pm
Author: huse_spud
that giant spudtech cannon has a 1.6:1 C:B ratio correct?

considering this, would it be more or less powerful if it had a say... 4:1 ratio?

Unread postPosted: Mon Jul 17, 2006 8:27 pm
Author: boilingleadbath
Pneumatics, excluding lighter-than-air gasses, won't give you what you want.

You might try a steel cannon using hot steam and a burstdisk.
The GGDT can model steam-propelled projectiles... preliminary estimates show you can acheive the speed of sound using 600 psi of steam in a 7' long cannon (2' chamber, 5' barrel, both 2" diameter) using a 70g projectile (wooden sabot)

I'd build an extra-large cannon just to be sure of it.
Such a cannon could be built for under 100$.
Teflon is rated for operating at temperatures of 500*F - which is about the temperature you have to get your cannon to to generate 600 psi of steam.
I'm thinking a sheet-metal shroud around the chamber of your cannon, with a strip burner along the bottom.

I'd have to look up the derating factor for steel at such pressures, but I don't think it's too bad - and 2" pipe can almost certainly be used, as it's rated for over 1000 psi at room temp.

Just be careful, though... you can probably imagain the burns supersonic steam at 500*F would give one!

Unread postPosted: Tue Jul 18, 2006 11:22 am
Author: Darkerweb12
I just had an epiphany, if you got some sort of temperature resistant burst disk, and filled the chamber 1/3 full with water, then got a few torches under the barrel, those would boil the water and produce steam enough to burst the disk.. just an idea

Unread postPosted: Tue Jul 18, 2006 4:36 pm
Author: Mihlrad
did this "epiphany" involve you learning to read the post above? You didnt think of that.

Unread postPosted: Tue Jul 18, 2006 9:00 pm
Author: jerb
lol I was thinking the same thing but i dint want to say it.

also on a side note, I have decided (under your advice) to put off this project due to the dangers involved. Im going to make a few more pnuematics and maybe a cool combustion instead

if a mod reads this: this thread can be closed/locked

Unread postPosted: Tue Jul 18, 2006 10:57 pm
Author: Mihlrad
good to hear, we dont think you cant do it we are just looking out for your safety and keeping the good name of spudding good. Eventually you will be ready for it, but build up to it slowly. You do have a great piece of property for spudding though it seems. Good luck be sure to post what you make ^^

Unread postPosted: Thu Sep 14, 2006 7:28 pm
Author: roderunner
I hate to tell you guys but you *cannot* break the sound barrier on compressed air alone.

Due to the laws of physics, air only travels at a certain speed. This is why the speed of sound is what it is. Even with near infinite pressure, the shock wave of pressure will only travel at the speed of sound. Thus unless one superheats* the compressed air, the potato will never exceed the speed of sound no matter what the pressure/volume of the compressed air is.

*As for superheating the air, that is what a combustion cannon does, and why the above does not apply to a combustion cannon.

Unread postPosted: Thu Sep 14, 2006 9:02 pm
Author: jerb
hmph... way to necro a rather old thread.

also Im glad you chimed in, but is conisidered general knowlage that you cant break the sound barrier with compressed air, I beleive it may have been noted in this very thread (prior to your statement)