SpudFiles

The plan is to make a microgun BBMG. Think of a GE microgun, but even more micro. I've got several drawings, but I'll either have to scan them on or redraw or render them in a program.

<s>I don't really want to reveal too much as of yet, I'd rather finish designing several versions of this BBMG before asking for feedback on how feasible people think it would be.</s> But I still have several questions.
This gun will fire 4.5mm lead BB's and a high ROF is hoped for (otherwise the design is purely wasteful) as well as being more efficient with air than a standard vortex BBMG.

In the current design, the chambered BB will only be exposed to pressurized air for a fraction of a second. Of course this would decrease performance, but how short of a burst of air is acceptable for a given pressure?

With the limited amount of air entering into the barrel, a barrel that is too long would decrease performance if the air behind the BB lost too much pressure (is this correct?)
Of course, a too short barrel will reduce performance too, as with any gun.
Aside from testings many different lengths (hard to do with my design) how do I work out the sweet spot? Would 30-40cm be ok? Shorter? Longer?

How long does it take for a vortex block to spin the BB's up to where they start entering the barrel and how much air is required to do so? (I'm guessing fractions of a second and depends on BB weight)

That's all I can think of now, I'll add more if I think of them, and change my design if any of the numbers won't allow for decent performance.

3VIL G3NIUS wrote:In the current design, the chambered BB will only be exposed to pressurized air for a fraction of a second. Of course this would decrease performance, but how short of a burst of air is acceptable for a given pressure?

Downloading GGDTand making virtual models with your own data will give you much more relevant answers to this question than any speculation by a forum member.

With the limited amount of air entering into the barrel, a barrel that is too long would decrease performance if the air behind the BB lost too much pressure (is this correct?)

Yes.

Of course, a too short barrel will reduce performance too, as with any gun.

To what extent is subjective

Aside from testings many different lengths (hard to do with my design) how do I work out the sweet spot? Would 30-40cm be ok? Shorter? Longer?

Again, GGDT

How long does it take for a vortex block to spin the BB's up to where they start entering the barrel and how much air is required to do so? (I'm guessing fractions of a second and depends on BB weight)

There is almost no delay between trigger and firing.

That's all I can think of now, I'll add more if I think of them, and change my design if any of the numbers won't allow for decent performance.

You should post your design in its early stages, especially if you have no experience with BBMGs - your plans could be resting on assumptions that might be erroneous.

Thank you for all that, I'd have a play around with that program, but when I attempt to open it it says 'failed to load 'CommonDialogue' from comdlg32.ocx, you're version of comdlg32.ocx may be outdated...'
strange...
Is this a common issue?

http://www.spudfiles.com/forums/ggdt-issues-t21983.html

http://www.spudfiles.com/forums/ggdt-help-t18786.html

Tried everything in there. still get error 372 and it doesn't work. This is running from an admin account on windows XP.

D_Hall wrote the program and is a member of this forum, perhaps he can help.

Well I PMed him, hopefully I can get it sorted. I've changed the topic name since I might as well discuss it until I can use the program, gives me something to do.

Current idea (although I have other backup ones) is that I have a vortex block set behind the rotating set of barrels. Hopefully on firing a BB would end up sitting in/behind the detent until a barrel goes past, at which point it will enter it and fire out, the release of pressure out the barrel with the BB will allow another BB to be drawn into place ready for the next barrel. Of course a passing barrel with a flat end would not allow a BB to enter it because of the small size and speed at which it passes. So <s>the aluminium ring that holds the barrels will be machined out to allow the BBs to enter much more easily.</s> if I post up a diagram it will make far more sense.
I still be believe there are several issues, but I like big guns, especially the look of a minigun. But I can't stand the ones which fake it with fixed barrels (whats the point? Might as well make a shotgun) Or with only one of the barrels working (just a standard BBMG with some extra barrels for looks)

I had a similar idea, never built it though. But now that I should be investing in a lathe/mill, hmm...



LeMaudit, add another project to the pile

Aww, I don't feel original now
anyway, I have a few nice lathes, milling benches at school along with nice thick bits of aluminium bar/rod stock.

How many RPM (revolutions, not rounds) were you hoping your barrel assembly would reach and still work?
I was thinking belt drive with a Tamiya electric RC motor 18,300RPM at best efficiency. http://fast-rccars.blogspot.com/2011/01 ... eview.html
something around 1:15 ratio to allow for around 7000RPM (rounds not revolutions this time) but was wondering if the BB feed would keep up.
Powered by 1 or 2 7.2v RC batteries (all of this I already have) and a speed control with trigger.

EDIT: more reading in the other thread, you say a BB is fed every 0.02 seconds in a vortex block, thats *only* 50 rounds per second, which equals 3000 RPM. I was hoping for more, maybe some insanely ruthless design would allow for more BB's per second.

EDIT EDIT: I was thinking of a way of using leakage at 150 degrees from the firing barrel (top one) so a small amount of pressure will load the BBs at the almost opposite side just after the BB in the top barrel has fired but before the BB in the barrel about to reach firing point gets to the top. As to prevent loss of air out a second hole at the time of firing (you'd need as much as you can if you are only getting a very small fraction of a second to get pressure behind that BB.

EDIT EDIT EDIT: my machined barrel entry would hopefully prevent shearing, and allow more air to be applied to the barrel for longer.

In your thread you mention 850PSI, I'm not quite insane yet, and I want portability, otherwise I'd make a freaking huge turret, something that would be possible to create without a small nuclear reactor in a backpack. Portable like the weapon that Nemesis uses in Resident Evil Apocalypse ( http://www.imfdb.org/wiki/Resident_Evil ... 27_Minigun ), rather than the modified handheld 7.72mm Miniguns in various movies such as predator (impossible due to weight). Of course a real weapon is limited by ammunition, but with 4.5mm BBs that is less of an issue.

So what do ya think? Should I continue?
Will I be better of throwing stacks of burning cash at the target rather than using that much ammo? Haha

edit: double post

Aww, I don't feel original now

Console yourself.

anyway, I have a few nice lathes, milling benches at school along with nice thick bits of aluminium bar/rod stock.

You'll need them

more reading in the other thread, you say a BB is fed every 0.02 seconds in a vortex block, thats *only* 50 rounds per second, which equals 3000 RPM. I was hoping for more, maybe some insanely ruthless design would allow for more BB's per second.

That was what Jimmy measured but other designs can go much faster. Have a look at this one.

If what you want is rate of fire, then I don't think a gatling gun is the right choice. The mechanical element is going to limit you, you're better off making a simple clould BBMG with multiple barrels and a suitably high flow feed valve, here's one I made.

EDIT EDIT: I was thinking of a way of using leakage at 150 degrees from the firing barrel (top one) so a small amount of pressure will load the BBs at the almost opposite side just after the BB in the top barrel has fired but before the BB in the barrel about to reach firing point gets to the top. As to prevent loss of air out a second hole at the time of firing (you'd need as much as you can if you are only getting a very small fraction of a second to get pressure behind that BB.

I can see the logic but again, multiple barrels connected to a cloud chamber are going to be the best idea for insane ROF-

In your thread you mention 850PSI, I'm not quite insane yet, and I want portability, otherwise I'd make a freaking huge turret, something that would be possible to create without a small nuclear reactor in a backpack. Portable like the weapon that Nemesis uses in Resident Evil Apocalypse ( http://www.imfdb.org/wiki/Resident_Evil ... 27_Minigun ), rather than the modified handheld 7.72mm Miniguns in various movies such as predator (impossible due to weight). Of course a real weapon is limited by ammunition, but with 4.5mm BBs that is less of an issue.

850 psi from a paintball tank = portability

What sort of power are you looking for - rather, what is it you would like to shred?

Here's the difference psi makes against a similar target with the same ammunition:

100 psi

800 psi

Of course, concentrated fire compensates for individual projectile power, but normally people strive for lower rate of fire and greater individual projectile power. BBs can get very expensive very quickly.

So what do ya think? Should I continue?
Will I be better of throwing stacks of burning cash at the target rather than using that much ammo?

It depends on what you want.

If you want a gatling with spinning barrels and aren't too bothered you won't have a rate of fire of 100,000 rounds per minute, go ahead with this.

If you want 100,000 rounds per second, make a cloud with multiple barrels firing simultaneously.

Hmm, well, I guess in comparison, a minigun with a lower ROF but using significantly less air is better, and less ammo. My flaming cash-wad gun idea shouldn't really have to become a viable alternative, although someone has probably already had such an idea.
I could always attempt to make it an almost exact replica of the Nemesis' Minigun, but the barrel length would probably be to short, depending on how much room inde the body of the gun could be used for more barrel length.
That would also allow an opportunity to make a replica of the rocket launcher too, golf balls possibly, but that's for another thread.

Paintball gun tanks are an option, but in New Zealand, where would I get them refilled? Would the local paintball gun clubs/businesses do it at a cost?

As long as it makes decent Swiss cheese of most stuff I'm happy. I could always run it at lower pressures until I either got bored and wanted more power, or for just general mucking around. It would probably be best to get a Paintball tank and just regulate it if I didn't want full pressure though.
I'm not planning on pruning trees or turning the neighbours car into a convertible at the moment, just enough power to shoot through your average targets of cans and plastic panels or peoples shins. I can always add more pressure, and it should be able to fire faster with more pressure too.

The lead 4.5mm BBs that my cousin uses in his pistols are apparently $12 for 500, Gamo BBs. I have found containers of 1500 for about the same price online, but they are probably eliptical, triangular and square, rather than round.

Anyway, I guess another great thing is that with correct engineering I could get a high ROF with less power per shot, or slow the gun down and get more power but save ammo. Plus it would be fairly unique, there doesn't seem to be many BB miniguns that are actually cool and functional floating around.
There is that silver one somewhere in this sub forum, only uses the top barrel and they don't rotate, plus IMO there is too much silver.
I think I saw one that some guy made with a standard AEG that fires through rotating barrels, clever and looked good, but not capable of a high ROF.
And a few commercial ones which are stupidly big for what they do. You don't need a 1:1 scale airsoft model of a 7.62mm minigun. It's too impractically sized.

I guess I'll try and get that simulation program going and draw it up and see if I'll be able to make it. Hopefully come back and post some blueprints

PS: those 1mm BBs must be the biggest PITA to clean up, even with a magnet. Very awesome gun though, crazy small caliber. Ever though of going to the opposite end of the scale and using watermelons or pumpkins?

3VIL G3NIUS wrote:Paintball gun tanks are an option, but in New Zealand, where would I get them refilled? Would the local paintball gun clubs/businesses do it at a cost?

MrCrowley is a fellow kiwi and moderator, he will suggest a fridge compressor

As long as it makes decent Swiss cheese of most stuff I'm happy. I could always run it at lower pressures until I either got bored and wanted more power, or for just general mucking around. It would probably be best to get a Paintball tank and just regulate it if I didn't want full pressure though.
I'm not planning on pruning trees or turning the neighbours car into a convertible at the moment, just enough power to shoot through your average targets of cans and plastic panels or peoples shins. I can always add more pressure, and it should be able to fire faster with more pressure too.

Standard shop pressures of 150 psi or so will happily shred cans, CD cases and other typical "soft" targets.

The lead 4.5mm BBs that my cousin uses in his pistols are apparently $12 for 500, Gamo BBs. I have found containers of 1500 for about the same price online, but they are probably eliptical, triangular and square, rather than round.

Lead BBs aren't reusable, I would stick with steel. Also, think about it, do you really want to spend over $1.20 for every second's worth of firing?

Anyway, I guess another great thing is that with correct engineering I could get a high ROF with less power per shot, or slow the gun down and get more power but save ammo. Plus it would be fairly unique, there doesn't seem to be many BB miniguns that are actually cool and functional floating around.

Yup, while the idea is not new there aren't many working gatling BBMGs around.

those 1mm BBs must be the biggest PITA to clean up, even with a magnet. Very awesome gun though, crazy small caliber.

They're practically dust, you can just sweep them up and discard. Literally dirt cheap and yes, small but "devastating":

[youtube][/youtube]

(that's single barrel rate of fire by the way)

Ever though of going to the opposite end of the scale and using watermelons or pumpkins?

If I had the space and money, BBMG would mean BOWLING BALL MACHINE GUN

As long as you don't get the HPA refilled somewhere after having used it with a fridge compressor it is a perfectly viable solution.

But then an operating pressure of 500psi would probably be more practical if the tank was filled with 850-1000psi. I'm sure 500psi would still be enough to get a certain amount of power with 4.5mm ammo.

jackssmirkingrevenge wrote: MrCrowley is a fellow kiwi and moderator, he will suggest a fridge compressor

Standard shop pressures of 150 psi or so will happily shred cans, CD cases and other typical "soft" targets.

Lead BBs aren't reusable, I would stick with steel. Also, think about it, do you really want to spend over $1.20 for every second's worth of firing?

Yup, while the idea is not new there aren't many working gatling BBMGs around.

They're practically dust, you can just sweep them up and discard. Literally dirt cheap and yes, small but "devastating":

[youtube][/youtube]

(that's single barrel rate of fire by the way)

If I had the space and money, BBMG would mean BOWLING BALL MACHINE GUN

Is there a thread on how to convert a fridge compressor into a suitable can refilling station? I'm assuming you just add in a few fittings and gauges to the right air hoses.
I think I'll try and go with dual paintball tanks, depending on how much they cost, I might have to do 1.
Hopefully have it all self contained inside the gun for maximum portability.
I'd want to model the aesthetics of it on Nemesis' Minigun, just because I like the look of it.

I was thinking of having the trigger control both the motor (on a variable speed) and an electric valve. I believe this would make it more efficient as a ball valve looks tacky for something like this, and a blowgun would restrict air too much and not handle 800psi.

If I am to spend so much time on making the firing mechanism, I might as well make it look nice and professional. I wouldn't care if it took me 6 months to make, as long as it is cool.

I love that video, and the barrel gun is cool too I think firing a 1mm tube would be more lethal than the BBs themselves. Haha

Would it still be considered a machine gun? The ROF from that would be very low, but it would make up for it with power. It would most definitely have to use combustion though, unless you can get a massive amount of stored air.