Blank Cartridges to Pop a Small Parachute

Sounds dangerous and liability heavy....maybe CO2 would be better.....?

"Usually we would use FFFFG black powder, and an altimeter to fire off the E-Matches that would pop off the body tube and deploy. I'm thinking that flying a UAV with an explosive charge would be a red flag situation. SO... CO2 ejection systems would probably be a better route for the hobby. Rouse-Tech makes one, the CD3, and it is mainly used for extremely high altitude flights where there isn't enough oxygen to burn the black powder and create enough gas to pop off the nose cone or booster section.

http://www.rouse-tech.com/recovery.htm

To activate it I guess you could use the servo switch the diydrones store has, hell you could probably write some code in the devboard or ardupilot to activate it in a no power situation or something..."

http://diydrones.com/forum/topics/how-to-make-recovery-parachute

https://fruitychutes.com/uav_rpv_drone_recovery_parachutes.htm

Parachute recovery system design manual....

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA247666&Location=U2&doc=GetTRDoc.pdf

Why don't you contact your local model rocketry club? Most model rocket engines include a small charge that pops the parachute out once the main engine has flamed out. Someone in the local rocketry club could probably give you some good advice on that, for what you need.

Model rocket ejection charges are black powder on top of the smoke charge of the engines themselves. So, That is not quite a solution. I don't really want black powder but the primer only type cartridges for theater use seem much better. I thought of using CO2 but that is expensive and heavy and prone to leaks an failure.

Spring loading is also an option and it may be the way I have to go. But I want to explore the blanks as an option because of the speed at which the cap on the chute tube can be deployed.

Yup. I say GA.

Another source would be sporting good store - ask for blanks used in starting pistols, or those used to train bird dogs.

making it official. ga

@Brave Sir Robin - I know, that's why I'm interested in them. Cheap and available, and reliable. But how much power do they have? I have no clue what to relate their ratings to, and I don't need much in a sealed tube to pop a cap and pull a chute out. It ain't like driving a nail! So, I looked for theater prop and racing type blanks, which have much less power but I still don't know how their ratings relate to what I'm doing. I've seen nailer blanks used to fire pelet gun pellets at supersonic velocities and that is a bit much for my needs.

My best example is the ejection charge in a model rocket engine. That is exactly what it is for and it works, But I don't need the rest of the rocket engine! I just need the charge. So, I'm back to theatre type blanks. Would these be sufficient without launching the cap so fast it rips the chute?

"My best example is the ejection charge in a model rocket engine. That is exactly what it is for and it works, But I don't need the rest of the rocket engine! I just need the charge."

This goes back to the model rocketry clubs. Talk to them, tell them what you're going to do, and they'll be able to help you. Odds are someone in the club builds their own engines, and can design a 'eject-only engine.'

You may also find they're a fun bunch to hand around with. If you've got parts from 'former RC copters' they might even help you make them into a custom rocket, so the copter can fly again, or even (if their rocketry field allows it, few do) they could design it so you could give your 'dead' copters a fitting send off buy building them into a rocket that uses the 'confetti' 'non-recovery' system.

I was a model rocketry man in college, but, you certainly have a better idea than a model rocket engine - GA for sure.

Agree with Usbport.

Rimfire blanks require a percussion blow to initiate the detonation of the lead styphnate primer material.

There may be a way to do this with an electric spark, but I use a hammer and firing pin.

Is that charge only in the rim or can I whack it anywhere on the base to fire it?

Only in the rim. A drop of liquid is dripped into the case and then the case is spun to deposit it on the rim.

Centerfire primers might also be an option, but I don't know how much power you need.

Ask the rocket guys.

I don't need much power, just a quick expansion of gas to pop the cap and drive the chute out of the tube, reliably! I need a quick reload and easy reset and shelf-life, and that is why a cartridge is a very good solution. I just don't know what the various "power" ratings on cartridges means in practical terms. I do know that the cartridges of nail guns is over the top for what I need, but I don't know anyone who has experience with the theater loads for stage guns. I have found primer only loads for use on indoor stage productions, but I don't know if they could pop a beer bottle cap or just a medicine bottle cap, and the youtube guys only test the nail driving cartridges!

OH! Your sayin' all I need is the primer! BINGO! Thank's Old Man! Perfect. I didn't know I could get just those! I could add a little powder to that if the primer alone is not enough and still have off-the-shelf materials.

GA from me Lyn! By the looks of it, all I need to load it is a hole in a breach. That makes assembly real simple. I know a few gun nutz and can get my hands on some of these for testing. Heck, I'll buy some myself.

I imagine each of these fits a different bore when loading into a shell? Wow, great selection of charges. The design could be adjusted for larger chutes and larger loads but with the same firing mech.

I'm thinking if I can insert a piece of coax into the opening at the front, then I can use a flyback circuit to set it off and eliminate servos and solenoids. Just send a high voltage jolt down the center conductor to the back of the primer from inside the primer cap, which is grounded.

Another GA for the list of primers brother!

The large and small primers are different diameters and shotgun shell primers are different again.

I've never reloaded shot shells.

Jesus Lyn you are on a roll. Shotgun shells are a perfect size for a small chute. If I just use the primer as the propellant, then I can pack the shell with a chute and a trigger wire to set it off. Nothing could be simpler or easier for anybody to obtain!

It looks like you're on a roll! Good luck with this.

Check out a marine flare pistol from WalMart or the big box sporting good stores. Costs about $50 USD, no permit required to buy if you are over 21, Must be manually cocked and fired by trigger put but battery powered servos could handle it. Made of plastic and fully self contained. Pull the flare and substitute a cork or balsa wood plug to eject the parachute. Rushes flares several hudred feet up so shouldn't be too much power for parachute ejection.

You could load the primers in a shotgun shell and stuff the parachute in the shell, it might work....

Primed hulls....

http://www.ballisticproducts.com/Hulls-all-gauges/departments/74/

https://www.quora.com/What-will-happen-if-you-fire-a-shotgun-shell-with-a-flare-gun

http://www.sportsmansguide.com/productlist/military-surplus/military-shooting/flare-guns-accessories?d=122&c=167&s=224

http://www.ballisticproducts.com/Rio-209-Shotshell-Primers-1000_box/productinfo/RIO209/

http://www.ballisticproducts.com/Universal-Primer-Pocket-Conditioner-10ga-410/productinfo/0740010/

I had the same idea chatting with Lyn. I'm liking this approach. Real damn simple and convenient. Shells and primers are everywhere. This is a really good maker type of solution, and that is what I'm looking to do. The circuit for electric firing can be just a toroid fly-back, a MOSFET and a resistor connected to an output on the flight controller. There is already a beeper output for emergency landings so you can find the damn thing. That same circuit and software can fire a chute too.

I like the shell idea because it is nearly completely pre-manufactured! You can pack a bunch of them and zip-tie them on and connect the wires whenever you need too. And you should be able to rely on them! You can use more than one for larger craft and get the same reliable results. Pack em' up and go fly. I love it!

It just occurred to me that I could use the recoil of the firing of the chute to disconnect the main battery and kill the motors. That would be very useful.

I just ordered some 12guage hulls from your first link. 50 for 13 bucks!!! I'll repost here when I have tested them and/or worked out a solution.

I want to thank everyone especially Lyn and SolarEagle for brainstorming with me on this. I really like this solution and I think I can make this work.

Don't shoot your eye out!

Just like Christmas morning....Oh boy!

The nail gun rimfire blanks from Hilti and the like can drive a 2 inch nail into concrete.

The loads vary per application.

Hit the back button on the link to see the different loads for Hilti.

Shotgun primers are the strongest. It will take a pretty strong spring or a long movement to fire the primers. A loaded shot shell will have far too much force and the primer may as well. In my miss spent youth we drilled out Empty 44 mag casings to take a shotgun primer and shoved them down into paraffin wax blocks to make a wax load. The idea was to use them pre paint ball to hunt each other with. They failed totally. A pair of jeans were laying over the padded back of a kitchen chair was the impromptu test target. The wax wad penetrated 4 layers of denim, the back of the chair, and 2 more layers of denim before splattering on the log home wall. Not sure the size of your chute but you will need to do some testing for sure. Looks like my iPad removes my spacing:-(

So you could not figure out how to use the rotational energy (or loss of it) to push out the parachute? The amount of force you need can be had from a simple spring made from guitar string. One would load the parachute over the spring, apply a blocking pin, and also provide some mechanism for loss of rotation of the motors to pull the blocking pin. How easy is that? I don't know, I have not tried it.

Something like a speed governor rotor? If the motors are all electric, which I presume they are, why not use a solenoid (parasite part of the motor current), to hold the last pin in place, and have a second solenoid act as a safety to prevent removal of the pin while the craft is on the ground and idle. The second solenoid would remove the safety block when the motors spin up (make this part irreversible to each sortie), then the second solenoid is actively holding the pin in place until current is lost.

The flight controller already has a "lost model" beeper output that can be used to "fire" the chute. What you don't want is a misfire during flight. An added benefit of the shells is the recoil. That can be used to cut the main battery from ESCs and force the motors to power down if they aren't stopped already by the software.

I think that you might be quite surprised at how much "POP" there is in such blanks, they have been known to kill while film making for example.

There are also special tools that use quite powerful "Blanks" to shoot steel bolts into walls and even into solid steel beams.....Someone here will know the names of such products in your area....I have forgotten!!

Keep us updated...

A friend of mine was once into "Quick draw" shooting. She used a .38 hand gun, with a smooth bore. Her ammo was primer only, with a wax bullet made by melting crayons in a bullet mold. She mentioned to me that if she shot herself, it was still quite painful... so even with primer only and a wax bullet, it had quite a bit of energy.

Bill

Thank you Sciesis2 for that story. That is the kind of info I need to relate. I have settled on the shotgun Hulls as the means. I can get them easily, and I can fit a chute into one, and there are a whole lot of wadding options as well.

I looked up the lead styphnate Lyn told me is used in the primers and found that it is pressure AND electrostatic sensitive, so I intend to use a flyback to fire it. For that, I have robbed the igniter from my grill! (I never use it because the battery was always dead.)

There are button igniters that are Piezo and need no battery.....they used to be easily found in US DIY stores the last time I was there....maybe eventually they could do the job as well?

They are found in grills here, but seldom as spares except from the OEM at higher cost than in the US!!

If there is a non battery way to do something, I tend to pick that.

I have one of the battery types, and it is lighter than a piezo and a solenoid and gear motor to press it. I have to have it work from a battery any way. It is not much more than a coil and core. My rough guess at the full weight of the chute and firing mech will be about 100g or less. A bit much for a 250 class quad, but nothing for a 450 or bigger. I'll be using it on a 650 class X8. This machine is about twice the size of DJI Phantom 3.

Let's just make this a whole lot easier:

Ask yourself what happens when ammunition ends up in a fire? It "cooks off" and goes off in all directions, right? Which part of the ammunition do you think actually is the least thermally stable? Look up autoignition and detonation temperatures of normal lead styphnate: Decomposition Temperature: Explodes at 270°C (518°F), autoignition point - no data.

SDS for Normal lead styphnate from Olin-Winchester:

http://www.winchester.com/SiteCollectionDocuments/pdf/msds/msds_w80.pdf

Here's my suggestion/solution: (1) provide a small rod of copper or brass to be in thermal contact with the rocket motor, and the primer button of the shotgun shell (nitrocellulose propellant granules, shot and wadding removed), (2) place a small amount of fire retardant cotton (treated) in the shell casing to reduce any potential for starting fires from cinders falling, (3) place the small packed parachute in close proximity to the shell (in its own close fitting tube, maybe even with a plastic disc for a plunger).

As the rocket engine burns through its charge, supposedly one could "thief" heat away from the last part of the burn by close coupling of the brass with the chemical reaction, the heated brass transfers this heat to the primer charge which ignites at the correct time (something like a fused delay), produces gas pressure, and releases the parachute.

Will this be consistent with your plans?

Alternative idea #2: heat pipe instead of solid brass rod, where the liquid medium of the heat pipe is a very high boiling liquid (has to be higher than the detonation temperature of the primer to work).

Alternative idea #3: devise a small thermopile (grouped thermocouples) with the hot end coupled to some of the heat from the rocket exhaust, but indirectly enough to have its own heat transfer time delay (i.e. - how long will the motor burn, and how long until the thermopile gets hot enough to generate sufficient voltage to pass detonation current through the primer?) This would require some careful (extremely careful experiments getting the burn time, transfer time, and electric current correct.

This is an emergency chute for a 300 to 800mm electric drone, not a rocket. I just need to limit damage to the lithium batteries in case of a failure and a long fall. The FAA limits my altitude to 400ft, but even a small 250 can weigh in at 500g and that is a big hit when it comes down. So I'm working on a simple electrically fired parachute deployment system that anybody can make.

So far the parts list starts with a cut-down battery operated grill ignition coil (fly-back) and shotgun hull for the primer and casing to hold the chute. I can energise the fly-back with an existing emergency signal from the flight controller, and ignite the primer with a discharge wire stuck into the open end of the primer inside the hull with the brass grounded to the other side of the fly-back and the negative of the battery system.

Good enough, I suppose somewhere I forget what the thread was really all about, and got back into "model rocketry days" mode of thinking. My humble apology for "droning" on about it endlessly.

And that is a small pistol primer.

Well put.

While visiting Gibraltar in 1968 on an HM ship, we all bought plastic (looking like a) 6 shooter (12 chambers and 12 caps), revolvers, took out the barrel plug and found that the cylinder chambers were unbelievably a reasonable fit for .22 air-gun pellets.....(a size common to the UK, but I have never seen them in countries NOT in some way connected with the UK!)

I do not remember how we found that out!!

Even just using the plastic caps, 12 in a ring shaped piece of plastic, they were quite dangerous, especially as none of us wore glasses (then!), or even owned or had safety goggles.....any of us could have lost an eye.

But the gun battles on the mess-deck were great, the ammo shot at you was easily re-usable, time after time and a quick change of the caps was really easy!!! In some ways, a bit TOO realistic, if one hit you on unprotected skin, it was a similar "pain" as paintball bullets I estimate.

You knew you had been hit.....

And that was even with this TINY amount of fulminate(?) in such munition, they still had a "spiteful" range of about 30 feet!!!

So I would expect that a shotgun primer to be really "over doing" it........ .22 blanks would be where I would start, and probably still too powerful.....

I looked on a website and found that airgun pellets in .22" format appear to weigh about a gram on average, if thats any help.....a small chute might not weigh much more if carefully made......even if it weighed 3 grams, it would still be shot out maybe 10 feet (forgetting wind resistance for the moment....)

As .22 blanks are rimfire, you have at least two choices, impact or heat.....or both for safety maybe?

Or better still, maybe an aluminium tube, with a good sealing plastic/nylon piston/sabot, could use a spring, as in an air rifle (but FAR smaller and far lighter), to "blow" the parachute out. No explosives at all, easily re "loadable" in the field....Just a thought!

Regarding using shotgun shells, you might want to put the shell in a chamber like a short piece of metal pipe... otherwise when the primer ignites, it might send pieces of shot gun shell in all directions rather than pushing the energy against the wad and parachute. Pipe size would depend on size of the shell, and should be a snug fit. Plus the base of the shell should be secured to the chamber to keep from blowing the shell out of the chamber.

Bill

I was thinking about that especially since the forum is providing caution as to the power of the primer alone. I think this is the soluton, but I also know I will need to do some tests of the pressures being produced and whether or not they need further containment. Perhaps a carbon fibre tube would be enough.

I'm hoping the shell itself, with an open end, will be enough. That would be optimum. However, I realize that this might not be achievable without some kind of barrel.

I might be able to get away with wrapping the open hull in tape. Anybody can do that, and perhaps achieve the goal, with the right tape...

I can get carbon fibre tape for 10 bucks at the hardware store that I already use to create frame parts. I Know from using it that it can wrapped around a hull to make a chute mortar. Or at least one worth testing. Heck, I can wrap it around a mold and create all kinds of chambers and shapes for chute tubes and such. Just wet it, wrap it and in 15 min you have a carbon fibre form with an acrylic epoxy base. You do not plan to fire too many chutes on your craft.

A little follow up on the internet research I've been doing. I found this video of a shotgun primer being fired under about 6" of water and filmed at 600FPS. In one frame it forms a bubble about 6" in diameter in just one frame. That is a lot of gas to come out of one little cap.

https://www.youtube.com/watch?v=13jdDCauKkU

Second, those of you who reminded me of model rockets gave me an idea to use a rocket engine igniter. My very first circuit ever was a rocket launch circuit with an "Armed" indicator light. It occurred to me that this may be preferable to the flyback method I was thinking of. The flyback coil is heavy, but I can fire a little igniter with just a mosfet and a signal and I can have an LED in series when it is armed to know if the igniter is "live" and ready to pop the chute when/if the time comes.

The MOSFET can sit parallel to the LED and when on will short the LED and fire the igniter.

I have hulls on the way, and I will see when I do my tests what it will take to contain the pressure and pop a chute without blowing up the copter!

Video/pictures please.

There is a link in the post.

This sounds like a good option, by using the ignitor wire, you will get thermal firing of the primer (you must make good contact, and also keep thermal mass low at the point of contact to the primer (metal if on outside). I do not think you will have casing coming apart as in the flare video, since this should not be taking place under water (water is non-compressible, and thus causes the exploding gas to develop far higher pressures than in an air contacting situation.

I found a video showing someone making their own primer and there was a paper cap over the grains of primer material. If the hulls I get have this paper cap then the igniter might not work.

But, I also saw a video where a guy uses an empty hull as a trip wire alarm, and he used a spring and a BB with the BB on the primer. Spring hits BB and BB sets off the primer. I could do something similar and so I'm sketching up some ideas on how to do that in a small space and with as few parts as possible. I'm thinking Neodimium magnets might be able to provide enough force. We'll see when the hulls get here!

The igniter wire whether placed outside or inside the shotgun shell (empty) with paper over the primer or without will work. Those wires have an additive on them that burns when the wire gets hot, and will set stuff of fire quickly.

I know, and back in the day when I did rockets they would sometimes fail to ignite the black powder inside the nozzle of the engine.

The problem is in the placement. I really don't like the idea of staring down the business end of the primer and shell and shoving something into it when the primer material is pressure sensitive. My thinking is coming back to hitting it on the correct side as it was designed for.

That is not a bad idea at all. Have you figured out how much impulse is required, applied to what size area yet? Obviously, trial and error on that might not be a bad approach either. I think it would be hard to produce "too much" impulse on the primer cap.

I agree. And I already know a couple of neos can snap really hard in the last mm of travel. That can make the mech short and lightweight. I can trigger it with a servo like the water rocket guys do with their rubberband chute deployment rigs.

I have 50 hulls on the way and a big collection of neos and a few servos. Should be fun this weekend if the hulls show up today!

You will need to protect the chute from the hot gasses produced by the ejection charge. You could try a shotshell wad or maybe a chunk of pink fiberglass.

I forgot to mention that safety glasses and heavy duty face shield are a must. The shield should be long enough to cover your neck. Don't want to be seeing this one on the news.

I used to do model rockets so I got the packing and wadding down pat. I also will test at a distance and with a full face shield.