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pico BBMG - 1mm calibre HPA

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 16, 2010 3:27 pm

Mr.Sandman wrote:Well then i have been misinformed, would there be any way of measuring its speed accurately without a chronograph? Or perhaps there is a special type of chronograph for smaller projectiles?


I had come up with this but energy lost breaking the contacts would likely result in a low reading. You could also have 2 discs rotating on a common axis at a known distance apart at known RPM. Shoot through the disks and by measuring the distance between the holes on the first and second disks, you know how much time has elapsed. Or a good high speed camera, but the sort of frame rate you need means that cheaper ones like the Casio I have would be useless.

I think you should order the SB07


Haha! Why not the pink ones :P :D

where do you get your 3mm steel balls for penguns


here, not cheap but beautiful quality.
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Unread postAuthor: Mr.Sandman » Tue Mar 16, 2010 3:35 pm

Hmm I need to convert pounds to dollars :D Perhaps i can find another source, if they make 3mm nail art :roll: If i can find some 1mm pipe then i will test your idea out, it sounds feasible but shall require some effort.
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Unread postAuthor: jrrdw » Tue Mar 16, 2010 3:44 pm

Mr.Sandman wrote:Hmm I need to convert pounds to dollars :D Perhaps i can find another source, if they make 3mm nail art :roll: If i can find some 1mm pipe then i will test your idea out, it sounds feasible but shall require some effort.


Paypal does that for you free of charge...

There is also a international shipping calculator, it will cost you $11.75 to ship a 5,000 pack to the USA. You can use the Paypal check out and as soon as your address is in there you will get the total in US dollars.
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 16, 2010 4:14 pm

In the US you're more likely to find 1/16" and 1/8" tubing and bearings so it might be worth looking for those dimensions.

I was thinking about getting 1/16" tubing to avoid jams but that works out at around 1.5mm, most of the BBs seem to be true 1mm diameter according to my vernier so I can't afford that sort of blow-by at this scale, it would be like using 6mm airsoft BBs in a 9mm barrel :roll:

I was thinking of conjuring up some sort of coaxial attachment I could fit into my drill to size the BBs quickly:
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Unread postAuthor: Mr.Sandman » Tue Mar 16, 2010 5:41 pm

jackssmirkingrevenge wrote:In the US you're more likely to find 1/16" and 1/8" tubing and bearings so it might be worth looking for those dimensions.

I was thinking about getting 1/16" tubing to avoid jams but that works out at around 1.5mm, most of the BBs seem to be true 1mm diameter according to my vernier so I can't afford that sort of blow-by at this scale, it would be like using 6mm airsoft BBs in a 9mm barrel :roll:

I was thinking of conjuring up some sort of coaxial attachment I could fit into my drill to size the BBs quickly:


Only problem i see there would be how to get the sized bbs out. And that would allow the perfect and the too small bbs to fit through. Although i have to admit that is a really good idea.
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Unread postAuthor: JDP12 » Tue Mar 16, 2010 6:39 pm

just thread the side of it and put a bolt in it
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Unread postAuthor: Mr.Sandman » Tue Mar 16, 2010 6:56 pm

JDP12 wrote:just thread the side of it and put a bolt in it
I guess that would work but still would take quite a bit of effort to get the bbs out, but then again they are 1mm. It reminds me of a video i saw of a guy who used a water bottle filled with airsoft bbs and soapy water to clean his bbs.
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 17, 2010 1:14 am

I could easily make a threaded cap in the main tube that also seals the inner tube, shouldn't be too much of a chore.
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Unread postAuthor: FULLMETALJACKET » Wed Mar 17, 2010 4:28 am

that wicked lil blaster has much muchness!

i think you have just found the cure for malaria in the third world!
now those roving hoards of mosquitoes and Tsetse flys dont stand a chance!

seriously that is awesome! my yards the play ground for phantom duceing cats n junkie scum. i needs sentry system!

the stealth if this has to be sweet. i imagine it hisses. no one would think twice about something that sounds benign. i want one of these for those boring bad weather days. it would make a sweet parlor gun. without having to worry about destroying my house with over spray. in this regard less is MOAR DAKKA DAKKA!
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Unread postAuthor: JDP12 » Wed Mar 17, 2010 10:19 am

JSR- have you considered making this into a CO2 inflator pistol prototype? the chamber is certainly small enough to do so and could be a potent little package.
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Unread postAuthor: Ragnarok » Wed Mar 17, 2010 11:11 am

Once again, JSR trying to prove that smaller is better.

While you've already failed to get a chrony reading, have you managed to work out the rough rate of fire? It'd be interesting to see how much size (and consequently, the square-cube law on the projectiles) affected ROF on vortex BBMGs.

~~~~~

And now, if you'll excuse me, there is something else to say...

Mr.Sandman wrote:Haha quoted and sigged.

Uh, yeah. On that note, the sig limit is 90 pixels high - about 5 lines, including blank ones (and any quote header).
You've got 8 lines there - while I'm okay with quoting in signatures, it gets very irritating if it starts to dominate reading a thread.

Getting rid of some lines so it was like this...
dewey-1 wrote:JSR; I think you should order the SB07's.
JSR & the Pico "Blue Balls"
This could be your new trademark! :D

... would be more acceptable (and within the rules).

Sure, it might be funny the first time, but after the eleventy twenteenth time someone sees it taking up more space than the post above it*, it'll just get annoying.
*Hence why I normally stay on a pretty strict limit of two lines of size 9 text for a signature.

Sorry to make my first new post in nearly two weeks a rant, but while I'm not posting much, I am reading - and that's going to make reading more work than it needs to be.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: dewey-1 » Wed Mar 17, 2010 11:51 am

Ragnarok:

I agree completely! I am tired of seeing this also.
Almost make me wish I had not made such a smart a$$ reply to JSR.
Even though he does deserve such actions!
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Unread postAuthor: ramses » Wed Mar 17, 2010 2:26 pm

IIRC, paypal charges for a currency conversion

Rag, what is the square cube law? I have a feeling the square has something to do with the area of the projectile, and the cube has something to do with the mass... Right?

Additionally, you could use a strobe light, photodiode, ruler camera, and sound card as a chrony.

Measure the duration of the strobe with the photodiode, a battery, and the sound card. take a long exposure of a burst with the camera in a dark room viewed by the same flash in front of a ruler, and measure the length of each streaked BB. you now know distance vs. time, the rest is easy enough
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 18, 2010 1:10 am

FULLMETALJACKET wrote:the stealth if this has to be sweet. i imagine it hisses. no one would think twice about something that sounds benign. i want one of these for those boring bad weather days. it would make a sweet parlor gun. without having to worry about destroying my house with over spray. in this regard less is MOAR DAKKA DAKKA!


Even at 800 psi it sounds like an ordinary shop blowgun, and the lauck of collateral damage from stray BBs is certainly a plus :)

have you considered making this into a CO2 inflator pistol prototype? the chamber is certainly small enough to do so and could be a potent little package.


Can be done, and the limited porting would certainly make the capsule last longer, though there might be freezing problems.

Measure the duration of the strobe with the photodiode, a battery, and the sound card. take a long exposure of a burst with the camera in a dark room viewed by the same flash in front of a ruler, and measure the length of each streaked BB. you now know distance vs. time, the rest is easy enough


If only I had the time to play with such setups :roll: :(
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Unread postAuthor: Ragnarok » Thu Mar 18, 2010 9:47 am

ramses wrote:Rag, what is the square cube law? I have a feeling the square has something to do with the area of the projectile, and the cube has something to do with the mass... Right?

Correct.
For a given radius, the surface area is proportional to the square of the radius, and the mass of proportional to the cube of the radius.

In this case, that means that doubling the radius of a projectile will halve its mass/area ratio.
As the force on the projectile from a pressure is proportional to its area, that means that acceleration from a given pressure is halved as well.

The square cube law is a big part of why smaller calibre launchers achieve high velocities with a shorter barrel than larger calibre cannons (quite aside from the fact that the smaller launchers can normally use higher pressures as well) - the mass/area ratio is higher, and consequently, so is the acceleration, and so therefore, they can accelerate to a higher speed in less distance.

Given that I'm more interested in kinetic energy which results from high velocity rather than high mass, that's why I personally prefer to use more modest calibres - it costs energy, but increases velocity.

In this case, I'm wondering how much the square/cube law affects BBMG rate of fire. The smaller BBs will presumably accelerate faster within the vortex block, but what does that actually mean for ROF?
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