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A new sentry gun project

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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A new sentry gun project

Unread postAuthor: evilvet » Sun Oct 21, 2012 12:49 am

Evening all.

Well, I finally did it; quit my contract job and giving myself six months long service leave. I have the entire summer off, probably well into Autumn before I go back to my day job. SWMBO has a range of projects for me to do round the house in that time but I have some other plans, one of which is this:
http://projectsentrygun.rudolphlabs.com/

The last few nights have got the Arduino and servos all configured so now the question becomes "what sort of shooter"

My thoughts are leaning towards:
Semi auto
6mm plastic BB's
Large ammo chamber feeding into a single shot solenoid activated breech
10 bar from the shop compressor or maybe using a BBQ LPG cylinder with appropriate regulator.

The idea of the breech/load mechanism is something like:
Detect target
Solenoid rod retract to allow a round to drop in under gravity feed
2nd Solenoid fires to vent firing chamber
3rd Solenoid cycles to refill firing chamber from the HPA reserve

I know it sounds like overkill but I have the bits and the electronics are a bit of fun.

Love to hear some suggestions from all of you, other things I have considered are:
Cloud BBMG
Some sort of blow forward bolt job
High pressure water squirter (fun for the kids in summer)

Cheers
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Re: A new sentry gun project

Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2012 1:18 am

Sweet!

evilvet wrote:Cloud BBMG


Definitely what I would go for.

Silly rates of fire guarantee a hit, and it's what most "sentry" type weapons today go for:

[youtube]http://www.youtube.com/watch?v=eEIGKkr68HQ[/youtube]

[youtube]http://www.youtube.com/watch?v=SGrJnxdDbO8[/youtube]

[youtube]http://www.youtube.com/watch?v=fYzZ4hz2wVE[/youtube]

If you're making it airsoft to be "safe" though, remember that a high ROF can be dangerous even if individual projectile energy is low.

Some sort of blow forward bolt job


Bit of a distraction while you're working sometimes helps :)
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Unread postAuthor: evilvet » Sun Oct 21, 2012 2:26 am

I knew someone would pick up on the subliminal BJ reference and of course it was you :)

My issue with cloud BBMG is a:) picking up all the little buggers later and b:) mowing the back grass and having a snow storm of spent ammo spraying everywhere.

What about some sort of bouncy ball 0.50 BMG round ?
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Unread postAuthor: POLAND_SPUD » Sun Oct 21, 2012 6:11 am

What about some sort of bouncy ball 0.50 BMG round
not a bad idea if you really want to injure someone

plus that's going to have some serious recoil, greater mass or the entire launcher and use lots of air... the first two are a bit of a problem as all of these sentry guns rely on servos

I'd go for a servo myslef if I could cheaply get these >>
[youtube]http://www.youtube.com/watch?v=8jajnIBX2cU[/youtube]
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Unread postAuthor: al-xg » Sun Oct 21, 2012 7:35 am

.50 bouncy ball would be fine, it's just like paintball gun, I'm not sure about a .50BMG bouncy ball though :D
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2012 7:39 am

al-xg wrote:.50 bouncy ball would be fine, it's just like paintball gun, I'm not sure about a .50BMG bouncy ball though :D


Well...

http://www.thefirearmblog.com/blog/2012 ... al-50-bmg/
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Unread postAuthor: Technician1002 » Sun Oct 21, 2012 10:16 am

If you are into electronics, you can build your own superservos. The schematics, printed circuit layout, and firmware are all online.
[youtube]http://www.youtube.com/watch?v=1qpc4G3NQhk[/youtube]
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Unread postAuthor: POLAND_SPUD » Sun Oct 21, 2012 11:24 am

thx for the vid technician but I already know all of that - sparkfun even sells assembled boards with preinstalled firmware

I am somewhat surprised that there isn't an off the shelf version of it... I wouldn't mind paying 2 or 3 times more for such a servo... If this was mass produced price could be just slightly higher than for regular ones. Sure there is this hall sensor but RC servos already have a microcontroller anyway

why waste $$$ on driver boards for step motors if you could just use a servo and tell it move to position A, then position B etc.

and let's face it thousands of ppl would love to have one too... so I can't really understand WTF the manufaturers are doing - it could be a huge market for them
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Unread postAuthor: Solar » Sun Oct 21, 2012 12:42 pm

http://www.flir.com/mcs/view/?id=53488

Above link is the pan tilt we will be using along with the system linked below.

http://www.watchstander.com/

I have been working on a design with selectable magazines that maintains a good center of gravity and utilizes a rapid fire to launch 40mm impact projectiles and gas rounds.

However... there are two other designs that are being developed at the same time as proof of concepts. One of which is a cloud gun that is comprised of a 40mm aluminum barrel and a 5 gallon plastic water jug hooked into a high flow source from a reservoir. I am awaiting a few hundred 40mm mini tennis balls to test it with. Basically it is like a lotto machine on steroids. It should provide a high volume with ease of reloading and be an effective deterrent. It will be used for strafing, non-pinpoint accurate use. After proof of concept a scaled up vortex block (6x) is the next project I am interested in developing.
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2012 1:06 pm

Solar wrote:However... there are two other designs that are being developed at the same time as proof of concepts. One of which is a cloud gun that is comprised of a 40mm aluminum barrel and a 5 gallon plastic water jug hooked into a high flow source from a reservoir. I am awaiting a few hundred 40mm mini tennis balls to test it with. Basically it is like a lotto machine on steroids. It should provide a high volume with ease of reloading and be an effective deterrent. It will be used for strafing, non-pinpoint accurate use. After proof of concept a scaled up vortex block (6x) is the next project I am interested in developing.


Ooooooh....

Must be one heck of a reservoir....
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Unread postAuthor: Solar » Sun Oct 21, 2012 1:28 pm

Still trying to determine the best air source. It will be on board a ship, so we have a lot of room to work with. I am going to start by trying a direct feed from a scuba tank into a larger diameter hose to allow for more lift and agitation on the balls. I would guess that a very large air tank pressurized to around 300psi would do well. A lot depends on what duration needs to be maintained to empty most of the rounds. Not sure if a backpack blower would provide the needed pressures but we might try that as well. I know a 16 HP electric blower/vacuum can levitate a croquet ball, but doubt it has the needed pressure. Some form of turbine might do the trick as well to sustain flow. The ammo is due to arrive tomorrow so I will know more after then.
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Unread postAuthor: Solar » Sun Oct 21, 2012 1:30 pm

And yes, I will post pictures and videos and I am especially interested in using the high speed camera to record the cloud action.
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 21, 2012 1:57 pm

Solar wrote:Still trying to determine the best air source. It will be on board a ship, so we have a lot of room to work with.


Ahh... we had touched on that idea vaguely here.

I am going to start by trying a direct feed from a scuba tank into a larger diameter hose to allow for more lift and agitation on the balls. I would guess that a very large air tank pressurized to around 300psi would do well. A lot depends on what duration needs to be maintained to empty most of the rounds. Not sure if a backpack blower would provide the needed pressures but we might try that as well. I know a 16 HP electric blower/vacuum can levitate a croquet ball, but doubt it has the needed pressure. Some form of turbine might do the trick as well to sustain flow. The ammo is due to arrive tomorrow so I will know more after then.


I very much doubt you'll get more than a couple of psi from a leaf blower. Ships usually have an onboard supply of steam or compressed air which would make more sense to tap, 316 stainless all the way of course.

As opposed to a cloud chamber with a lot of dead space, you might want to be feeding air and projectiles from a tube. Alternatively, store the gas and projectiles in the same place and put the valve between that and the barrel.
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Unread postAuthor: POLAND_SPUD » Tue Nov 20, 2012 10:15 am

here is an idea I had a few months ago after seeing one of these:
[youtube]http://www.youtube.com/watch?v=4eZVGvScbqg&feature=player_detailpage[/youtube]

it's basically a mortar/launcher platform based on a similar system:

1. gun mounted on a universal joint attached to the baseplate
2. two cables attached to the barrel and the two step motors. The motors and their pulleys are anchored to the ground
3. third cable attached to a spring or a rubber band

all the cables spaced 120 deg apart - some maths&coding and you've got a system that can fire in any direction and reach elevations of at least 90 to 40 deg

Just thought I might share it here

EDIT
any idea what's the formula for driving the motors called ? or how to find it ? I found it a long time a go but now I am lost where
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 21, 2012 12:55 am

A sentry mortar?

Your greenhouse is DOOMED!!!!

hehehe

Soooo... can we expect a Polish bodged together version of this anytime soon?

[youtube]http://www.youtube.com/watch?v=v5wE1HEtSLQ[/youtube]
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