OK, looks like we have a new way to entertain the kids and wreak havoc in the neighborhood, if this spark-shooting ferrocerium cannon is as easy to build as it looks.
This one comes to us by well-known purveyor of eyebrow-singing projects [NightHawkInLight], whose propane torch never seems to get a break. The idea here is a large scale version of an apparently popular trick where the “flints” from lighters, which are actually rods of ferrocerium, an aptly named alloy of iron and cerium, are heated to a nearly molten state and dropped onto a hard surface. The molten alloy thence explodes in a shower of sparks, to the mirth and merriment of those in attendance.
[NightHawkInLight]’s version of the trick scales everything up. Rather than lighter flints, he uses ferrocerium rods from firestarters of the type used for camping. The rod is stuffed into a barrel formed from steel brake line which is connected to the output of a PVC air chamber. His ominpresent propane torch is attached in such a way as the flame plays upon the loaded pyrophoric plug, heating it to a molten state before the air is released from the chamber. The massive display of sparks seen in the video below is pretty impressive, but we’re getting tired of gender reveal parties and forest fires. We just hope he had fire extinguishers on hand.
Seriously, be careful with stuff like this. [NightHawkInLight] has a lot of experience working with these kinds of projects, from his plasma-propelled soda bottles to making synthetic rubies with an arc welder. We’re sure he wouldn’t want to see anyone get hurt.
Stop using pvc for air chambers.
Sounds like you don’t have the best day today
Can I use it for potato canons?
“Stop using pvc for air chambers.”
But if you do, rest it against your crotch…
What are your preferred alternatives?
ABS. It doesn’t shatter if it explodes, it just tends to “split open”.
Something other. It may be weaker, but you could wrap it in some cloth (doesn’t need to be glass cloth) and apply epoxy. It will make part more strong and when it does break, you don’t have shrapnel.
Any pressure vessel is a bomb. One of my best Mechanical Engineering professors always said that. So much that is burned in me. Totally agree. Certain materials are bad choices. If one cannot calculate the hoop wall stresses or be bothered to learn, one has no business designing anything with a pressure vessel. Explosions are why the ASME was founded. While the chances here maybe aren’t worth worrying about, complacency can kill you.
You sound exactly like someone else I know named CW, who insists that noone around him really knows anything, because they don’t have his grand pedigree of design mastery.
He is one of the most obnoxious and insufferable people calling themselves a maker I’ve ever been forced to listen to.
Now here as you- obviously pressure vessels are dangerous. PVC though has been used in this fashion because there are, just like with other materials, known ratings for it. It’s best to use welded steel, but PVC can safely be used if there is a relief valve placed in as an intentional failure point if overpressurized.
I don’t like it either- but a few generations of backwoods makers who grew up doing something even more dangerous, and using PVC as a combustion chamber, have proved it can be done safely if careful.
pipe outside diameter = 2.375in
pipe wall thickness = 0.154in
pipe max working pressure = 280psi
From the video, he’s filling it to 50psi.
Seems fine to me. Maybe I missed something? He cycling the tank a couple thousand times or something?
PVC has pressure ratings for water. Are you saying it can’t handle air? And water hammer can really abuse it which is why the burst pressure is 4 to 5 times higher than the working pressure. 2000psi for 1″ schedule 80. This isn’t rocket surgery. https://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html
Quite cool!
But I would try to get rid of the open flame. It might be feasible to heat the ferrocerium through induction?
It spews the molten metal used to start camp fires everywhere…I think the horse has left the barn on fire safety here.
In other news, once he figures out how to dope the ferro to color the sparks, the gender reveal party people will love this.
That is a fair point. ;)
Although there is of course a difference between an open flame and a bunch of sparks. For one, the sparks are temporary and are shot away from you. While the open flame is close and can burn you instead of the others.
But in any case, using induction would allow for the use of an Arduino for building a trigger mechanism, so that would be a plus too. :D
I was thinking the exact same thing and just dug out my good’ole 1000w zvs induction PCB, 8mm id x 10mm id quartz tube and put in an order for 8 5/16″ x 3.1″ ferrocerium rods from amazlut lol
Ah, the innocence of today. This was my favorite book in the Junior High school library. Page 447 and call your therapist. http://www.sciencemadness.org/library/books/projects_for_the_amateur_scientist.pdf
My copy of this book has been a treasured possession since high school, appreciate the link to digital version I can add to my library.
It seems a little irresponsible to do this in a grassy and wooded area given that *fire starter* is literally in the name of the product it’s made from. The material is still actively reacting when it lands in the grass. That could get less than entertaining very fast.
Next to pine tree no less. Let’s hope it rained recently there.
I do have to agree. This thing is better suited for Great Britain, where there are only a few days per year that it doesn’t rain.
California Wildfire in a can!
ABS not PVC. Shattering happens. Dragon’s Breath also happens.
Without safety goggles
hmmm
WARNING! Gory special effects description follows.
I’ve seen it used by a special fx crew to simulate a gunshot wound in a zombie film. A painted and made-up plaster cast of the actor’s head and shoulders, with weaknesses built in to the skull, connected to PVC pipes coming up the throat with (IIRC) epoxy resin sealing it. There were blood bags behind both weak points – one small one for the entry wound, and a large one at the back of the head for the exit wound.
Two cameras at the front for the entry wound, one wide shot and one closeup, and one closeup pointing to the rear exit wound.
Lots of warning calls, and “clear” from the various operators, cameras running, pressurise the chamber, “action”, and the effect almost worked. The weakness in the rear was meant to blow right out, produce a big hole, and spew a cloud of blood and goo towards the camera, but it didn’t work properly, and only blew off what looked like a flap of (fake) skin.
Boy was the Director pissed off! The FX crew had assured him it would work, so they only made one model, and they spent an hour trying to patch it up for a second attempt – which, of course didn’t work very well at all.
But the PVC didn’t fail, it was improper preparation of the head.
“But the PVC didn’t fail, it was improper preparation of the head.”
You mean in the minds of the FX crew?
B^)