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long range ammo MiniBoy Mark I

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: MrCrowley » Thu Jul 28, 2011 6:29 am

jackssmirkingrevenge wrote:Nice... so we have a date set for the perforation of the stratosphere?

Next opportunity is mid-semester break in August-September. The Rugby World Cup is also being hosted in NZ at the same time so i'm not sure if we'll take a trip up to the bach. After that, semester end in November :(

Though I'm sure I can convince everyone to go up for a night or something in the mid-semester beak.
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Unread postAuthor: LeMaudit » Thu Jul 28, 2011 7:09 am

Now you've just demonstrate very clearly that when a canon do "click click" and not "BOOM", one must NOT look into the barrel to check why :-D
Looking good indeed!!!

c) Yes, that is a girl who screamed

Yeah, right! Nobody believe you :D
No need for you friend to be ashamed about his high pitched voice. Some guys made their career with that... hum... feature... singing opera...


Next opportunity is mid-semester break in August-September

no rush... plenty of time to experiment some magic way to retrieve the shiny thing.
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Unread postAuthor: saefroch » Thu Jul 28, 2011 9:17 am

LeMaudit wrote:no rush... plenty of time to experiment some magic way to retrieve the shiny thing.
I highly doubt it'll still be shiny after being rammed into silica, zircon and alumina powder...
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Unread postAuthor: ramses » Thu Jul 28, 2011 7:35 pm

LeMaudit wrote:No need for you friend to be ashamed about his high pitched voice. Some guys made their career with that... hum... feature... singing opera...


You call this music?.
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Unread postAuthor: LeMaudit » Thu Jul 28, 2011 7:41 pm

I was more thinking of... that.

[YouTube]http://www.youtube.com/watch?v=NWMOmBohlTE[/YouTube]

Though the missing "feature" may be related in both cases.
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Unread postAuthor: Fnord » Fri Jul 29, 2011 12:53 pm

Hey Crowley,

I'm going to be a whiny b**ch here and ask you to please avoid holding on to the barrel like that when firing the miniboy. With a blank shot it's not really a problem, but the pressure the barrel sees will be a lot higher with such a heavy projectile. Sorry, even though it's ABS I just don't think you have enough safety factor to be doing that.
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Unread postAuthor: MrCrowley » Fri Jul 29, 2011 4:07 pm

Actually, I do share your concerns. I've never been 100% sure that I would fire it myself or remotely, it's just something that's been in the back of my mind. I'll have to think of a stand that can hold it in place, I guess.

The heaviest projectiles I have fired were about 100g in weight, MiniBoy will be 150g minimum. Considering the difference in recoil from firing a golf ball (45g) to a frozen lemon (100g), the step up to 150g is sure to be significant.

HGDT says 9,500J and 1100PSI barrel pressure for a 150g projectile compared to 1000PSI for a 100g projectile.

Edit: I'd also be worried about the end of the barrel failing after the barrel support, you can see how much it flexes just from a blank fire in the video.
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Unread postAuthor: LeMaudit » Fri Jul 29, 2011 4:33 pm

keep it safe MrCrowley... no matter what...
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Unread postAuthor: MrCrowley » Fri Jul 29, 2011 4:35 pm

What about wrapping the barrel in fibreglass? Do you think that would give me a more significant safety factor, Fnord?
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Unread postAuthor: DYI » Fri Jul 29, 2011 4:43 pm

Well Crowley, since the section your worried about the failure of is simply a cylinder, the fiberglass method is a reasonably good one. A thick, solid wrap will certainly protect your hands and reinforce the base of the barrel against rupture. You need not do the whole barrel, but adding a wrap in the area you hold would probably be worthwhile.
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Unread postAuthor: MrCrowley » Fri Jul 29, 2011 6:00 pm

I'm surprised how cheap it is. In your opinion, how thick should I wrap it?

1mx1m

10mx0.07m

Not sure if the 1mx1m sheet would be enough, the second link should be plenty but has a less convenient width.

Edit: I could always cut the 1mx1m sheet in half and wrap only the first 50cm of barrel. Thickness would probably be around 10 layers if I did that.
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Unread postAuthor: warhead052 » Fri Jul 29, 2011 9:47 pm

MrCrowley wrote:Actually, I do share your concerns. I've never been 100% sure that I would fire it myself or remotely, it's just something that's been in the back of my mind. I'll have to think of a stand that can hold it in place, I guess.

Edit: I'd also be worried about the end of the barrel failing after the barrel support, you can see how much it flexes just from a blank fire in the video.


A few garage springs, maybe 10, and a nice welded steel frame to hold it up, and your good to go. The springs will simply be recoil absorbers, so you can fire it remotely and know that nothing will get damaged badly.
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Unread postAuthor: MrCrowley » Fri Jul 29, 2011 10:32 pm

Well I figure it's easier and cheaper to go the fibreglass route, so no stand required.
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Unread postAuthor: ramses » Sat Jul 30, 2011 8:27 am

I think garage door springs are way to stiff anyway.
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Unread postAuthor: Fnord » Sat Jul 30, 2011 10:45 am

Crowley,

I'd say you'll want to add a layer at least 5mm thick near the chamber end. It probably isn't necessary to wrap the entire length of the barrel that thick, as the pressure is highest in the first couple feet. Wrapping the entire length would help reduce the flexing somewhat, though.
Depends on how much you want to spend on it.
Fiberglass, properly applied, should have a tensile strength of anywhere from 40-60 kpsi. That's in the same range as heat-treated aluminum.
Some cheap polyester resin will do as an adhesive.

edit... although I think you should at least brace the gun against something for the mini boy shot, mainly just to steady your aim and avoid the inevitable trigger flinch. I guess leaning it against your ATV would be enough.
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