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unposted cannons

A place to ask general spud cannon related questions.
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Unread postAuthor: Ragnarok » Sat May 03, 2008 6:45 pm

spudfarm wrote:and both of you never posted those?

Well, I wasn't asked that, but Behemoth was made before I even joined this site.

EDIT: Nope, Behemoth never exceeded 200 psi. Still a good lot of power though.
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Unread postAuthor: DYI » Sat May 03, 2008 7:00 pm

Heck, I know my cannons are small fries in the world of kinetic energy, but it doesn't stop them being a truckload of fun.
I'm an advocate of energy through velocity rather than mass, partly because it allows launchers to be closer to "the real thing".


Velocity really does help when you get into the higher ranges, but you're not likely to achieve very high velocities with room temperature air. Even hybrids are limited to Mach 3 or so in general, still will below the point where the interesting effects start to appear.
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Unread postAuthor: JDP12 » Sat May 03, 2008 7:05 pm

i haven't posted any of my guns which include an advanced propane metered golf ball gun, a marble machine gun, a hybrid, and my two BBMGs. I really should post these..
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Unread postAuthor: SpudFarm » Sat May 03, 2008 7:07 pm

post them here NOW!!!!!!!!!!!!!!!

one more hybrid on the team!
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Unread postAuthor: Ragnarok » Sat May 03, 2008 7:14 pm

DYI wrote:Velocity really does help when you get into the higher ranges, but you're not likely to achieve very high velocities with room temperature air.

Indeed, the highest reading I remember getting from HEAL was about 1030 fps with a 3.4g paintball. Still fast, but far from rifle speeds.

But I'd sooner have the 500 J from a 25g object at 200m/s, than a 100g one at 100 m/s.

In reality, as efficiency lowers with higher muzzle velocities, you'd probably not get the same energy in two weights so separate, but still, even with the losses, I'd take the lighter, faster projectiles - It's just more fun to me.
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Unread postAuthor: DYI » Sat May 03, 2008 7:20 pm

But I'd sooner have the 500 J from a 25g object at 200m/s, than a 100g one at 100 m/s.


And I'd sooner have 1kg at 400m/s than 25g at 200m/s :P
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Unread postAuthor: SpudFarm » Sat May 03, 2008 7:20 pm

not if you are building a hybrid to send a 45g projectile at rifle speeds ;)

DYI nailed it..
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Unread postAuthor: JDP12 » Sat May 03, 2008 7:23 pm

i'll post them as soon as I convince my mom to take pictures of them.. or i'll see if i can use my sisters camera.
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Unread postAuthor: SpudFarm » Sat May 03, 2008 7:26 pm

can you "spec me up" on the hybrid?
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Unread postAuthor: Ragnarok » Sat May 03, 2008 7:42 pm

DYI wrote:And I'd sooner have 1kg at 400m/s than 25g at 200m/s

Yes, but can you achieve that from something even close to a practical "rifle" size? :D

Not to say I don't envy the energy levels of the SCTBDC, but I couldn't hope to get more than about 1000J from a smallish cannon like HEAL or even the step-up from that 3vo when it's done.
As I don't want my cannons to get larger than they already are (actually, I have built larger {Behemoth of course}, but shrunk the size back again for HEAL), there is something of a power ceiling to contend with.
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Unread postAuthor: DYI » Sat May 03, 2008 7:53 pm

Yes, but can you achieve that from something even close to a practical "rifle" size?


Give me $2k, and I can pack that much power into something the same size as HEAL. The problem with doing that isn't a power ceiling, it's something called "the shooter being instantly ripped in half from shear recoil energy".
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Unread postAuthor: D_Hall » Sat May 03, 2008 7:54 pm

Ragnarok wrote:there is something of a power ceiling to contend with.

Say's who? :D
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Unread postAuthor: SpudFarm » Sat May 03, 2008 7:56 pm

please not hijack
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Unread postAuthor: JDP12 » Sat May 03, 2008 8:29 pm

yea i can, its extremely similar to SB15s, same configuration(i have his permission). 1.5" steel nipple for chamber, i forget the chamber volume.. somewhere between 20 and 30 cubic inches. I had a 1" union on it, but it is being replaced with a cam lock because i'm sick of the union leaking. now i haven't fired this yet, i'm super busy with school. once school lets out (May 16), i'll be able to test it a lot more extensively.


I'm also working on two more amazing guns, (not hybrids) that i will be building this summer. they will be amazing, i promise you. hopefully you'll all be blown away
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Unread postAuthor: Ragnarok » Sat May 03, 2008 8:34 pm

Give me $2k, and I can pack that much power into something the same size as HEAL.

80 kJ from HEAL's size would need some fairly funky engineering.
Considering HEAL is the size of a Barrett M82, which only has a fifth of that muzzle energy... not impossible, but you'd need solid propellants.

There is a power ceiling of sorts, as the materials available can only withstand so much. Sure, 3000 psi helium could be used to achieve insane velocities, but if the launcher can't safely be used at those pressures, then it's not an option.
Accounting for an acceptable safety margin in the materials and with all practical limitations considered, I can't foresee more than around 1000 joules being achievable from a launcher that size under practical parameters, and I think that's already generous.

Of course, I could get thicker pipe, or steel rather than copper... but there is still a limit there, just a higher one.
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