View Full Version : Centrifugal Gun
08-16-2001, 12:08 AM
Anybody know about the legality of these things? The Poor Man's James Bond by Kurt Saxon (Yes, I do have a copy. No, I do not live in Montana, or wear a black trench coat [well, I haven't worn it since Columbine].) has plans for building one. Basically, it spins a BB around and then slings it out the barrel at high velocity. Saxon wonders what the ATF would think about this since its silent and doesn't involve gun powder.
I know that if some wacko used one of these things to start offing people laws against them would be passed immediately, but are there any laws prohibiting them currently? Or can they be covered under current laws (i.e. those dealing with a concealed weapon) for the most part?
08-16-2001, 12:48 AM
Off the top of my head, I suspect they would be treated like airguns. After all, adult air rifles can easily break the skin with their pellets; the big ones are used in small game hunting and are especially popular where noise is a no-no (e.g., you're purging your toolshed of four-legged squatters but you don't want the neighbors to think there is a war going on). Bows (and airguns which launch arrows) can obviously kill people, as can pellet guns with a bit of bad luck. Yet none of these are ATF regulated.
On the other hand, they are commonly regulated at lower levels of government. You can't walk around the mall with Browning compound bow in your hand; a flamethrower is a big no-no (although it's not legally a firearm, etymologically perhaps); airguns are subject to city ordinances. For the ATF not to regulate a weapon is really a matter of bureaucratic division-of-labor; local laws tend to be pretty restrictive of the sorts of weapons which scare people (butcher knives are fine while switchblades are not; ballpeen hammers are fine while blackjacks are not).
08-16-2001, 01:41 PM
Heh, tell Saxon to get a load of this puppy (http://www.resonanceresearch.com/prod06.htm).
There's many ways to fire a projectile, including a bow and arrow. IANAL, but there's gotta be laws that cover projectile weapon in general.
08-16-2001, 02:37 PM
Here's a link to a letter from the ATF about "Potato
Launchers" which basically says "context counts".
08-16-2001, 03:05 PM
I'm having a bit of trouble envisioning this device working. First, having a chamber spinning fast enough to launch a pellet is definitely going to make noise. I don't remember all the rotational kinematics I was taught in physics 101, but I'm pretty sure that you'd need a fairly large disc spinning pretty fast. Not easier to make in your garage, probably impossible to keep quiet. Second, it's going to exert a constant pull on you, ruining any chance of aiming. Don't even consider the accuracy if you could aim, because it's going to be a low-velocity shot, with a lot of energy wasted getting the thing into the barrel. Third, it's going to take time to spin up to a reasonable speed, on the order of seconds or minutes. It's going to make noise in the process of spinning up. It's going to make noise spinning down, or even more noise if you try to brake it. Don't even get me in to what it will look like, carrying around the batteries, the motors, and the disc, then setting it up. Good luck making the thing even marginally man portable. Last, but not least, consider this. A bullet, from an air rifle or a gun, is under acceleration from breech to the muzzle. This gun gets all its acceleration at once, much of which it will lose getting the barrel and into the rifling. I could go on in this vein for days.
The physics are bad, the logistics are worse, and the chances of killing someone are slim. If a wacko, as you put, builds one of these good enough to off people silently, he's going to be snatched up by weapons designers ASAP, a la Project Paperclip.
In short, it seems to me that the ATF doesn't regulate them for the same reason they don't try to regulate Venusian Death Beams: Good luck finding one to regulate. There have got to be literally thousands of ways to kill people silently that do not involve improvising a poor substitute for an air rifle, which is both louder and larger by at least an order of magnitude. Of these ways, I'd guess most could be found in the span of hours anyplace in the world, and most would probably be much, much more effective.
Then again, you could buy some cord and a leather patch and make yourself a sling (a solution proven effective over many thousands of years). But I don't think that's what Mr. Saxon had in mind.
08-16-2001, 05:37 PM
You have described a bad version of the sling of David and Goliath fame. Accurate and deadly, but only with lots of practice. Good range too. Still used by Palestinians.
08-16-2001, 06:57 PM
In Ca. there is a penal code section 12020p.c. which is basically a catch-all type section that covers weapons or devices that are not list seperatly under sections. I would guess that most states have similar section on their books.
08-16-2001, 07:10 PM
Trucido, a man portable version might be difficult. I'm posting from a friend's house, so I don't have the book beside to give a more accurate description of the device, but a version was built which was capable of hurling a good sized ball a distance of several hundred yards and at that distance it penetrated a heafty piece of wood. I'll post the specific details later when I get home and can look them up.
Certainly, the device won't be silent, but I doubt that it would be as quite as loud as a gun shot. Additionally, one could rather easily encase the thing with insulation to muffle the sound.
As for lugging batteries around, one could theoretically build it so that the gun ran off the cans of CO2 that they use for paintball guns. This would probably cut the efficiency way down, but might make a more practical version.
Thanks to google, I found a site (http://cdl.library.cornell.edu/cgi-bin/moa/pageviewer?coll=moa&root=/moa/manu/manu0021/&tif=00011.TIF&view=50&frames=1) which has a piece on a slightly different version than what Saxon was talking about, but the principle's the same.
08-17-2001, 12:18 AM
Okay, back home. Here's the sentence describing the "high powered" one I mentioned above:
[A] gun which shot two-inch balls 150 yards through three one-inch pine planks and landed from three to four hundred yards beyond, powered by human muscle.
And here's a quote from an article which appears to be from Scientific American that Saxon reprints, describing some of the physics of a man-portable version (emphasis in the original):
This may set you thinking of the potential of a centrifugal gun whirled by a gas turbine at, say, 20,000 RPM. With an effective swing radius of about 6 in., you'd get a muzzle velocity of over 5000 fps -- better than a high powered rifle!
Judging by the link Larry Mudd provided, I'd say that if you got arrested while having one of these things in your possession (even if you didn't use it) would get you in a serious bit of trouble, once the authorities figured out what it was that you had.
08-17-2001, 01:08 AM
Have any of you seen any of the videos starring Saxon and his "science"? It's hillarious and scary at the same time. He'll have you believing everything ([b]EVERYTHING![/b}:eek: ) in your kitchen is explosive! You'll be afraid to make a tossed salad fearing the dressing ingredients will blow up!
08-17-2001, 02:23 AM
Tuckerfan, I keep doing the math, and I'm not getting 5,000 feet per second. The outer edge of that 6" spinning disc will be traveling at 1,048 fps. How will it accelerate a projectile faster than that? Additionally, that is not a MUZZLE velocity, it is a BREECH velocity. All of the energy has been imparted to the slug before it leaves the barrel, and a great deal of this energy will be absorbed by the slug as it interacts with the rifling and the barrel. I would be surpised if it retained even 30% of its kinetic energy initially imparted, even less from something as long as a rifle barrel. You have even more problems, in that you must transfer the slug from the spinning disc to the barrel, if you intend to do that. In a traditional firearm, the bullet is already in the barrel when fired. The barrel for this gun must withstand the full stress of the bullet striking it, and a slight misalignment will likely rip your barrel off. Okay, you say you can deal with all this. All right, bust out the 20,000 RPM gas turbine. Good luck paying for it, good luck muffling the turbine scream, and better luck finding a heavy truck to cart it from place to place. Don't even get me started on the fact the time and lakes of fuel you'll waste spinning the thing up. You'll likely need a secondary starter turbine, and/or starter motors. This is not a plausible thing to build.
This is all beside the point, though, and I must apologize for hijacking. Anything you use as a weapon will be treated as such by the law. If you build it and play with it where nobody can get hurt, like as not you won't be bothered. Start pointing it at people, and you'll have legal trouble, guaranteed.
08-17-2001, 06:36 PM
Trucido, I don't mind the hijack one bit as I'm curious about the physics of the whole thing as well. I haven't been able to find a good link which shows a detailed pic of the design of the thing, but from the illustration in TPMJB, it looks like the ball is slung into the barrel just after the top of its arc. As for the 20,000 RPM turbine, there's air powered tools which run at 40,000 RPM (or some other absurdly high number) which can be hand held (admittedly, the compressor can't).
How exactly are you doing the math? I'm not saying that you dropped a decimal or anything, but its been a while since I played with those kinds of numbers and I forget the formulas.
08-17-2001, 08:33 PM
I started with finding the circumference of the swing radius- a point on the outside of the radius, which I will assume is the projectile, is traveling that circumference for every rotation. Therefore, for every rotation this point/projectile will travel pi*12", or 37.74". 20,000 rotations per minute multiplied by 37.74" per rotation equals 754,800 inches per minute. Dividing by 60 gives us 12,580 inches per second. Dividing by 12" per foot gives us my figure of 1,048 and 1/3 feet per second. So we have our projectile along the rim of the swing radius. As soon as it is released, it begins to slow down. That's why I can't see how one could get 5,000 fps out of one of these projectiles.
If I can bring myself to do it, I'll dig out my copy of Brassey's Guide to Military Small Arms. I think it might have an equation for the energy that will be lost interacting with the barrel, though I can't quite imagine how you're going to get the projectile into the barrel.
I would be very careful hooking something six inches long to an air tool traveling 40,000 RPM. Even micro die grinders (Which'll go over 50,000) will NOT give that RPM if you burden them with a swing and projectile. For that sort of application, I couldn't find much better than 5-6K RPM. The whole system will be dangerously unbalanced, and, as I said before, it's going to pull you along with a mind of its own.
08-19-2001, 05:24 PM
The model in Saxon's book has a counter weight to try and counter act any instablity the gun might have. I don't doubt some of your conclusions as to the physics behind the whole matter, I've had some questions myself (that's one of the reasons why I've posted them here). Still, a relatively small model should be safe to build, I think.
08-19-2001, 09:14 PM
A counterweight won't do much, might make matters worse. You need a counterrotating disc of equal weight for stability. A small model will likely be safe, as long as everything is firmly attached and shielded.
08-19-2001, 10:49 PM
A bearing locks up and no one should be anywhere near one of these. Like an inertia starter from old radial engines, they get real messy when they do that.
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