Sentry Gun Project

[POLAND_SPUD]

well it doesn't look that bad

forget about that 1mm ammo... switch to 4.5mm or 6mm BBs...

ohh today I got those 0.3g BBs that I ordered...
and damn... you were right
heavier ammo = worse feeding

it isn't much worse but it is annoying so I have to work on this

the good news is that the power has improved quite a bit

[jackssmirkingrevenge]

forget about that 1mm ammo... switch to 4.5mm or 6mm BBs...

That was a tempting thought but there are too many advantages to using such tiny ammo, plus I have about 70,000 rounds in stock

I think for my next trick I will try a much longer barrel, screw compactness. I've also ordered some small neodymium magnets, maybe they would be useful as a detent

ohh today I got those 0.3g BBs that I ordered...
and damn... you were right
heavier ammo = worse feeding

well...

it isn't much worse but it is annoying so I have to work on this

Since you're going with 6mm, have you considered modding an airsoft magazine?

the good news is that the power has improved quite a bit

I can imagine, 0.25gBBs were certainly better than 0.12gBBs in my 6mm burst disk launcher.

[POLAND_SPUD]

airsoft magazine

yeah I'd love to but I don't know how to seal them and how to mod them for 300+ psi pressures

AFAIK there is a sort of coiled tubing housed inside them so it seems I might as well use the idea you posted earlier

[jackssmirkingrevenge]

It depends on the type of valve, if you're using a detent that needs the chamber and magazine to reach the required pressure then yes, the magazine needs to be sealed.

If you're using a pulsing valve however, as long as the magazine is feeding into a section of 6mm tubing before the breech, you don't need to seal the magazine because the BBs in the tube aided by the spring resistance will more or less seal access to the mag.

[POLAND_SPUD]

ohh that's what you meant... yeah I've been thinking about something like that for quite a long time but I'll use a DCV for that or a timer circuit... anyway that's something completely different than this

you've mentioned that you've used polyamide tubing as a magazine.. how well does it work ? well if you can't coil copper tubing then what stops you from using a length of tubing as the magazine ?

ohh I have an idea... I'll post a pic of it soon

EDIT
naaah I just realized it won't work

[jackssmirkingrevenge]

you've mentioned that you've used polyamide tubing as a magazine.. how well does it work ? well if you can't coil copper tubing then what stops you from using a length of tubing as the magazine?

2mm tubing as a magazine didn't work for the 1mm BBMG, as my recent mishap illustrated the BBs flow out well enough without the barrel at the end of the tubing, but once I put that in they jam.

On a side note, I dug around my HPLC spares drawer, found what looks like 0.75mm I/D silicon tubing looks like I'll be fitting a detent after all hehe

[POLAND_SPUD]

yeah I can understand that.. I've just realized that one of the fittings I used to build the detent has ID equal to 2 X times the bbs OD.. so it is not surprising that it causes jams... I wonder if it will improve feeding by a lot

I think that you should use tubing that's 1.5 X times the OD of the BBs... that is 1.5mm in your case

[jackssmirkingrevenge]

True, having the BBs pass through tubing that is exactly double their O/D is asking for trouble. Sadly I only have 2mm polyamide tubing available.

Still, when I get home I'll do some single shot testing with a longer barrel and the silicon detent to see what the power potential is with the setup illustrated below. Who knows, the pressure buildup might cause a big enough flow of air to shock it into working reliably

[jackssmirkingrevenge]

re-think N^o. 27,043:

It seems that even when working well, the 1mm BBMG is still fairly weak and I want a bit more ooomph from the gun element (yes, POLAND_SPUD, I guess you were right )

Conceptually the Otomatic SPAAG is a good analogy:

It is worth mentioning that modern SPAAGs are usually fitted with 20 - 40 mm guns. Such a powerful gun was selected because of it's long range. The Otomatic can engage helicopters at 6 km range, before they release their anti-tank guided weapons.

Not a huge step up but significant enough, I'm thinking 3mm calibre with a sealed adjustable detent to maximise pop-off pressure and reduce rate of fire in order to limit it to a short burst (5-10 rounds) per trigger "engagement".

[POLAND_SPUD]

3mm ? naah... go for 6mm (or at least 4.5mm...)

let's face it - at one point it will shot someone or something accidentally so make sure you can use some 0.12 or 0.2 airsoft rounds as ammo

Also with this calibre it's easier to build a gun (remember kubaT1000's gun ?). What is more if you get bored with it you can sell it to some local airsoft enthusists for a good price
....not to mention that technically it would be an airsoft turret so if you get caught with it you can say 'it's just an airsoft turret'

[jackssmirkingrevenge]

I want a projectile that can be easily missed in case it strays out of my shooting area, 1mm is perfect for this as it's practically dust, but it's too much of a compromise on power. With 3mm bearings the projectile is still pretty insignificant in terms of dimensions, but 27 times heavier that the 3mm so the jump in power is considerable.

I don't really want to go any higher than that though, I'm scared

What is more if you get bored with it you can sell it to some local airsoft enthusists for a good price
....not to mention that technically it would be an airsoft turret so if you get caught with it you can say 'it's just an airsoft turret'

Even airsoft needs a license here so I'd be screwed anyway.

Besides, I want to do *some* damage... otherwise I'd stick with the 1mm.

It shouldn't be too hard to make, small cloud type chamber for 50-100 rounds, seal and ball detent.

[Fnord]

You know, I'm pretty sure there are webcam programs out there that can recognise and track the shape of a human moving across a field of view. All you need to do is find an open-source one and ask someone to program it to give USB output signals based on the track box x-y coords (wouldn't be hard at all... a novice programmer could probably do it).

Then add one more signal when x && y =< 30 or so, and that will be the solenoid valve Muahahaha I need to stop now im getting too many crazy ideas

[POLAND_SPUD]

I still think it's a better idea to build a proper 6mm version. something tells me you won't be satisfied with the performance of 3mm ammo

At least you would have a chance to test davidvaini's idea (hopup unit). Though if I were you I'd use a solenoid valve + timing relay as the firing mechanism, not a bv

@fnord
I know I've already said it over 400 times or so but RC servos are not up to the job. I'd love to see even the simplest decent turret that uses geared down DC motors (or step motors) for controlling both axes. Then you can make it do just any kind of stuff you wish.

[Crna Legija]

re-think N^o. 27,043:

It seems that even when working well, the 1mm BBMG is still fairly weak and I want a bit more ooomph from the gun element (yes, POLAND_SPUD, I guess you were right ).

hahah reminds me of this

[jackssmirkingrevenge]

You know, I'm pretty sure there are webcam programs out there that can recognise and track the shape of a human moving across a field of view. All you need to do is find an open-source one and ask someone to program it to give USB output signals based on the track box x-y coords (wouldn't be hard at all... a novice programmer could probably do it).

I already linked to a free version of similar tracking software here

I still think it's a better idea to build a proper 6mm version. something tells me you won't be satisfied with the performance of 3mm ammo

In my experience 3mm + HPA = win

I know I've already said it over 400 times or so but RC servos are not up to the job. I'd love to see even the simplest decent turret that uses geared down DC motors (or step motors) for controlling both axes. Then you can make it do just any kind of stuff you wish.

Again, if you're making a TRAP style sniper system firing accurate single shots, or an indirect fire artillery type turret that will hit a specific GPS coordinate, by all means this would be a better idea, but for this project it's a needless complication.

-_-, I had seen that elsewhere, and it's a very good analogy for the 1mm "sandblaster"

This is what I had in mind for the launcher, nothing too innovative or complicated: