My EE friend thinks the entire thing is laughably simple to do and fit for junior high kids to design.  I'll probably just put the resistor for 5s on it for now.  

I'm a bit busy today, but think I can get the boards ordered and a Form 1 filed tomorrow.  I don't need a F1 for the fuze, but I am going to blow something up with this.  

Now we need a digital countdown timer labeled,"The Holy Hand Grenade".  And it needs two modes, visible light & IR.  

Mechanical/burning fuzes were 3-5 sec, historically, I believe.  You could add an impact disabler, so if the grenade is dropped on the floor or bounces off a tree immediately after the fuze is activated, it shuts down.

IIRC, the 2nd WW Japanese grenades were activated by banging them on a rock after the safety pin was pulled, making it the first use in history of,"A rock or something."

I don't believe that's a smart plan, with respect to me, on their part for a bunch of reasons, some of which you know.  

The classic T97? They were. Assuming the firing pin was screwed down and the grenade was being carried armed that's all you really did. Although to be fair the usual procedure was to yank the cord - not ring - attached to the safety pin and then smack the head on your helmet not usually "a rock". That would crush the thin brass cover and move the striker assembly which of course would set off the primer and start the delay train. Exceptionally simple and nearly foolproof.



More details at Inert-Ord.net.

My grandfather who was at Buna had a story about those:  The natives figured out explosive fishing with Japanese grenades they picked up after battles.  Pull pin, slam grenade on the side of you canoe, drop into the water.  A couple of them killed themselves with U.S. and/or Australian grenades, by pulling the pin, lettting the spoon fly, then beating it on canoe waiting for the pop/sparks/smoke they expected from the japanese ones.

This is exciting stuff.

Shame I’ll never get an explosives license at my home address.

I have a solution a few hours away for the future though.

Poor bastards!

Now I'm picturing a flounder yelling "Grenade!" and throwing himself on it to save his buddies.

Now I'm considering putting "killing asian carp and zebra mussels" on the F1s box i.

ETA: I have F1s for other stuff where I put "impressing women", "robot terminator defense" and "dinosaur hunting".

internet goofy replies aside...

1. A poster above is correct. Unless it’s solely for smoke, this is pointless without a fairly safe binary primary explosive that can be mixed relatively easily and quickly. If the whole point is to have a legal fuse... then the point is to travel with it. LOTS of stuff is legal if it’s for personal use and you don’t travel with it or store it... I mean, like LOTS. You can synthesize C4, RDX, PETN, lots legally, and detonate it. So.... If the goal is a legal fuse, you would probably need have a legal boom method. When you have that - and let me know if you find a binary primary that could create blasting cap force - then you’ll know what kind of fuse you need. Without a legal primary, you would need an illegal primary... well.... at that point you might as well have an illegal fuse too.

2. Unless it is ONLY for smoke... you are about to fuck up if you use some bullshit ATMEGA chip and aren’t an expert programmer. I am. I have seen lots of issues with micros doing unexpected things that you miss. In this case, your DETONATE NOW gpio commands may run when you don’t want them to. With smoke, no issue, with anything else, goodbye hands or face or whatever. This IS NOT a job for a single normal micro. This is a job for a safety micro, a single chip that has two CPUs that run either separately or the same code at the same time in “lockstep”. Or, two completely separate micros that run coordinating code. One set of code will check conditions and make a determination to “fire” and trigger a mosfet, the other will check all those  conditions (EDIT) on separate circuits in the same way and after a slightly longer delay will “fire” by shorting your lithium battery into the wire or electronic match or whatever through that mosfet. Both micros had to separately determine the right conditions then coordinate on a firing where both have to agree. You still need good code. You still need good circuits. You still need a trigger and fire method that makes sense for your primary, but you get a little redundancy from EMI or static or just some shitty chip that momentary runs code it’s not supposed to while a clock is stabilizing or because of some sleep or wake interrupt code.  

I’m sure it’s not enough, but some components like tantalum explode (you would have to shave the case down, and even then probably deflagrate) when the fail. And iirc there is someone with a device that simulates a pistol shrimp’s claw that actually creates a small explosion from separating hydrogen from oxygen and creates an ultra tiny plasma effect. I do wonder if there is a clever detonation source that has been overlooked. But again.... it’s pretty moot at point 1. No sense in doing it legal for travel unless it’s smoke because as far as I know, simple flash power might be the best you could get and I don’t know if that would do much except a “legal until the ATF sees it” flash bang. And simple flash powder doesn’t detonate so much as it does burn really fast, under a hammer this might be enough for a secondary but alone, uncompressed, I’m not sure it would do much. And I’m also not sure a flash powder ball would do anything but sound loud. If you want to sound loud there are civilian firecrackers in flash bang shape for air soft ready to go with grendade fuse-like pulls.


EDIT: Thinking about it for a second more... unless you were doing something trick and REALY needed the logic of a micro, I would avoid that. This is a hardware circuit problem and needs a hardware circuit solution. I would only use a micro if there was some extra logic signal like an accelerometer or something like that. Otherwise, all you are doing is adding a catastrophic failure point for no reason (your shitty code in a shitty micro). The spoon or button or switch or whatever would be critical to shunt the circuit, you would need some short protection so that there is no way it can go off unless all these other things line up correctly, etc. If the only thing the micro is for is to be a counter... ffs, use a capacitor circuit or a timer IC or IDK anything else. I’d even consider making the firing portion isolated from the trigger portion with an optocoupler or something....... but then again..... that Japanese design is beautiful in its simplicity and safety assuming you can’t crush that striking tower with the pin still in it.

"Battery/SPST/electric bulb in a hollow shell - here's my $200 and F1 for a landmine."

It'd be interesting to see how they try to justify the inevitable denial.

I'll sleep on it. Might be worth doing.

On my long list of projects, is smoke and illum rounds for a 60mm mortar.  I believe electronic fuzing is the way forward.

I imagined a unit that initiated a timer on setback, and functioned on apogee, or even functioned after a few milliseconds of delay (I want a smoke round that traces the entire trajectory).  Alternately, setback then impact.

I have also applied this line of thinking to 40mm.

Why do you want smoke to trace back to the mortar?

You're a bad person for putting that in my head again.

Did you know that there are existing federal laws regarding SAMs? 18 U.S. Code §?2332g.

When I did submit a F1 for exactly such an arm, the ATF instantly denied it and sent a couple of FBI agents to come interview me. That was 2005 IIRC.

I didn't like their explanation - and I still say that an approved F1 would count as "under the authority of the United States or any department or agency thereof or of a State or any department or agency thereof".

What about a TOW?

Because it would be fun, and look cool, and I could visualize the entire flight path of the mortar. I could fire projos with charge one, two, and three in rapid succession with different colors and paint rainbows in the sky.  Because if I can't blow stuff up, I still want to have fun. Because I have a motherfuckin' mortar.

No reason, really.

Smoke tracers for 40mm grenade launchers is on my to-do list as well. DangerousBob told me how he does it with the 40mm before rounds and bigger stuff. I need to see if it will work with low velocity rounds.

I see the primary explosive issue.  I have some ideas there I'm not quite ready to discuss, but I will point you towards the patent literature on non-toxic priming compounds as a start.  

There's still some interesting possibilities of purely replicating what can be done with an igniting fuze or practice grenade fuze.  

With respect to a microprocessor and issues, all jokes about using a raspberry pi, I wouldn't depend on any hobbyist micro for a safety critical function you're holding in your hand.  I could pretty easily see that with an industrial PLC or medical device controller board, which would have redundant watchdogs, and multiple safety functions.

For this round, I am using a pure double timer timing circuit, and I can run all of the EMC testing against it.

I am leaving through holes in the PCB to connect the output end to a controller, be it simple or not.

I've got boards ordered, and F1s ready to go in today or tomorrow.  Two of them are close, abet with much bigger boom, to the landmine idea, one is a grenade.

That's sort of the basic plan on the grenade.  On the other F1s, I have explosive mixtures of fuel and air that a hot wire will easily ignite.

I do think there's potential for a binary primary explosive, and that's a path worth going down at some point.

Somewhere, an EE just got the wildest look in his eyes...and is drawing squiggly lines on the back of a receipt from his pocket...while google searching various electrical components and reaching for his visa card...

I'm glad you plan on using black powder - at least at first. FAE and similar are a bit more iffy to deal with around electronics. At the very least please thoroughly pot everything in resin after conformal coating. I shudder to think what the tiniest little screwup leading to a spark would do as both liquid and gaseous fuel tends to be unforgiving in the extreme.

An odd thought occurred to me just now. I've noticed that for both LBDD and EXDD black powder is very commonly overlooked. I wonder why? It's relatively cheap and available and it's certainly easy to make. Along with that it's legal to store some monstrous amount with no permit or particular magazine legally required. I think 50lbs is the cutoff for "sporting/cultural" uses.

ETA: It is.

Agreed - Americans are ornery like that. A nation full of contrarians!

The law doesn't say "you can't do it" - it only says "you can't do it this way".

You and I both know that however long that takes they will lose.

I just wish they weren't making your life so very interesting in the meantime. I swear you must have stepped on someone's toes back in the day and now they work for the ATF.

I'm not that afraid of sparks on a low voltage circuit with minimal components, which, as you said, can be potted.  I would be, as discussed above, much more worried about flashover from a pyrotechnic fuse train.  

It's not rocket surgery, plenty of medical stuff is designed this way for use in explosive environments (anesthetic gases or sterilants) and I can go belts and suspenders approach and fill any remaining space in the fuze with silicone so only the hot wire is exposed.  In terms of the risk of blowing MYSELF up, at least one of the FAE ideas is easily remotely filled with gas mixture.

I disagree with the ATF on Ben's fuze, but they will have a harder, or at least different argument with a device that is filled with small arms propellant BP immediately prior to use, and an even harder one if the BP is made on site, which isn't a big deal to do.  

OST

we need can cannon timed triggers

We built a kinda nasty mod for night scenario paintball games

we modded cardboard disposable film cameras into strobes that were built to make night vision users avoid locations

i was kinda funny to have them go off from a tripwire at 1am

you could see the woods light up

there is a lot of power in a simple camera flash

You plan on milling and corning BP on-site? Or just going in dry (fine powder dry mix)?

Right? That's a little silly. You can buy/store/transport black powder legally right up until you load it into the grenade. At that point it no longer falls under any exemption.

Are you thinking increment charges?

Sounds like non-fixed ammunition to me.

I've milled and corned BP before, on the site that I would probably blow up a grenade, so its an option.  

I don't think that's necessary, but its an option, and probably one that would scare the ATF more than just using commercial propellant.  Think about what the ATF does with AP pistol ammunition and pistol brace regulations, where things that were designed for one purpose are "redesigned" if an end user uses it for something else.  

I get it now. I really like that idea - what possible legal argument can they have against it? Make them basically say "well we just don't want you to do this though" plainly. Outstanding!

This will go a lot easier when you assume I'm doing parts of this purely to make their arguments as laughable as possible in front of a judge in about a year.  Otherwise you're going to think I'm mildly retarded.

Two thoughts- what is it about consumer fireworks that exempt them from this binary requirement? We are allowed to store them as non-binary without an FEL, both fused and kinetic types. Could this fuze be accomplished while staying under the requisite explosive weight limits, and still adhering to whatever federal regulations allow those?

Secondly- Im picturing some kind of quick-attach fuze- that uses maybe neodymium magnets or perhaps some kind of ratcheting device like the dead air silencers use (but cheaper and more basic)- to attach the fuze to the grenade body. Something that takes a fraction of a second to attach together and will hold even if it the whole thing hits a wall literally. Machined in such a way that once the thing is attached it is very difficult or impossible to separate again.

1. The ATF just lost their bump stock case at 6th circuit.  The relevant part, at least to simpletons like me is that they got smacked down arguing Chevron deference.  M228 and bump stocks have a bit in common as far as regulatory flip-flopping and deviating from actual U.S. code though someone like nolo would have a better guess there.

2. My guess is that if I were to F1 a pressure cooker and say I'd fill it with commercial fireworks, our friends would argue that when I bought fireworks to fill it, the fireworks lost their exempt status when I had the state of mine to "design" them into an explosive DD.  It is bad sophistry from the DMV of the federal government.

3. Thanks for all the advice and discussion.  If Ben hadn't stuck his neck and persec out a little I probably wouldn't either.  

Ummm - hand grenades were used in the US Civil War.  They are small arms.  You're designing a fuze for an antique small arm, which is a particular American cultural celebration of freeing the black slaves from their Democratic Party oppressors.

Why redesign the fuze head to grenade body attachment? It takes but 2 seconds if that to screw on the fuze to the grenade body. What I think needs to be re designed is the primary & secondary explosive in the detonator cap that attaches to the fuze head stem via a quick attachment (crimping). The explosive in the det cap ideally would be a binary that is capable of detonating ammonal or ANNMAL that is the filler for the grenade. Having a binary in the det cap should exempt it from magazine storage and FEL requirements just like how anyone can buy tannerite and store it anywhere they like as long as it isn't mixed.


Edit: Scratch the second part, crimping the det cap would just be easier.

I'm struggling to follow that edit. Crimp what?

I think an electronic match (and right this is a job for a PLC, but even then seem my big post, you don't want to write firmware for a micro or hardware config for a FPGA/PLC unless you HAVE TO) is the easiest part. Getting to anything "legal fun" would be hard and the issue revolves around the train.

But agreed it would be dump to redesign the coarse thread in favor of an ungodly complex mating assembly.

I was trying to see if installation of the detonator cap would be easier with another method of threading in place, but it's not. I over complicated it.

So ideally you have your fuze head with the delay and primer installed but without the detonator so as to keep this fuze as disassembled and not needing magazine storage or an FEL. Then when you're ready to use the grenade, you mix a binary explosive on site, fill the det cap, install it over the fuze head stem, and crimp it in place. Then you fill your grenade with binary filler as well, and boom.  

The binary explosive that is to be used in the det cap is what needs to be looked into. It needs to be insensitive enough so friction doesn't set it off, but strong enough to set off AMMONAL or ANNMAL. That is if you want to create a fuze that doesn't need to be stored in a magazine or need an FEL.