Like the ball mill, this is another project I've been working on for some time. After being inspired by a friend, I decided that I absolutely had to have one of these delightful toys. In principle, a coilgun works by using a coil (duh!) to create a strong magnetic field which pulls a ferrous projectile forward. As the projectile enters the center of the coil windings, the coil turns off, releasing the projectile on its deadly flight.
To store the energy for the intense magnetic field, I used 17 disposable camera capacitors arranged in parallel. These capacitors are charged by four identical camera capacitor charger circuits whose outputs are wired in parallel to the capacitor bank. The inputs to the chargers are wired in parallel to a normal-duty switch, which connects the charger inputs to four AA batteries, also in parallel. All this parallel-ness makes the capacitors charge faster and lets them dump more power all at once into the coil.
The "trigger" for this coilgun is a heavy-duty (20 amp/250VAC) switch wired between the coil and the capacitor bank. While this setup works decently well, I have noticed that the switch contacts occasionally weld themselves together from the massive (possibly lethal) amounts of electricity being flung across them. I may fix this at a later date with a better solution.
To make the coil, I took ~90 feet of 30AWG wire from a microwave oven transformer secondary/high voltage winding. I cut this in half and twisted the ends together to make two strands in parallel. I then wound this around a pen tube with two acrylic end stops 30mm apart from each other. I did 10 layers this way before sealing the wires tightly in place with hot glue. The coil began 30mm from the frontmost part of the end cap of the pen.
The projectiles I am using are 30mm sections of 1/4-20 bolts and 30mm sections of 6mm steel rod. They work really well and are cheap. I placed some of them in a copper sulfate bath (after a brief cleaning dip in 25% H2SO4 and then in aqueous NaOH) and then polished them to give them a shiny copper plating, which adds to the "authentic bullet look."
As you can see from the video, it's a pretty fun toy! To wrap up the project, I did a test measuring the projectile drop in altitude versus the distance of the shot to calculate the muzzle velocity. As it turns out, this gun has a 12 m/s muzzle velocity with a 7g steel bullet. The bullet then has a kinetic energy of 0.5 joule. *Sigh* Ah - it's still fun even if it's weaker than a BB gun.
After years of anticipation, I finally succeeded in making iron thermite, the king of infernos! I used the aluminum powder from Experiment 35: Ball Mill & Aluminum Powder for Thermiteand the iron (III) oxide from Experiment 37: Making Iron (III) Oxide for Thermitemixed intimately in a 1:3 mass ratio. The resulting mixture was a somewhat golden color and had the consistency of flour. I placed the powder in a depression dug in a pan of sand and lit it with a 2" magnesium ribbon. The reaction exceeded my wildest expectations - it was an utterly brilliant ball of orange flame, totally engulfing the pan with its furious power. Check out the video below for footage of the event:
Also, I have now started a Summer of Thermite playlist on YouTube, so be sure to subscribe to my blog by email or to my channel via YouTube to keep up with these firey experiments. I plan on doing many more reactions similar to this one.
After the slag cooled, I removed it from the sand and broke it into fine pieces using a hammer. For the most part, it was bubble-filled glassy alumina that easily fractured. In some pieces, I found small blobs of iron produced by the reaction. I cleaned the black oxide off the pieces of iron using vinegar and then swished them around with sand to abrade off other surface contaminants. After weight the resulting product, I was absolutely astonished to find out that I had only recovered 16 grams of iron from the reaction! Without even calculating anything, that is a terrible yield, considering I converted over 200 grams of iron in my iron (III) oxid
e producttion. But since I like chemistry, I did some simple stoichiometry to reveal that starting with 322 grams iron (III) oxide, the theoretical yield would be 225 grams iron metal, so I got a 7% yield. I believe most of my iron flew up during the reaction and rained down to earth as tiny iron droplets. Honestly, though, the yield is of little concern to me considering how exciting the reaction was. :)
In the last experiment, I made fine aluminum powder, with the intention of doing the thermite reaction. The most common type of thermite is the iron thermite, and its second ingredient is iron oxide. Both red and black iron oxide will work, but I used red (iron (III) oxide), because it was the most common and I saw good instructions on making it. Basically, the process involves running electricity through iron electrodes in a brine electrolyte until one electrode is completely eroded away. This produces rust from the iron. I switched the polarity (+12V and ground) of my electrodes every 12 hours to even out the erosion and make the cell last longer. After 36 hours, I drained the excess water and baked the sludge at 400°F for an hour. I then ball milled the product to a fine powder. I also made a video showing the system I developed of making red iron oxide in large amounts (it works quite well):
Although blowing up hydroxy-filled bags and creating shotgun-level bangs was fun, the end result of the last experiment was that I burnt out my lab power supply. To remedy this situation, I acquired another ATX PSU from a friend and converted it, this time with some added flair.
Previously, I used two packs of overpriced binding posts from RadioShack. Each pack had one red and one black, which meant that for three positive voltages I either had to buy even three packs or just use a black post where a red one should have gone. I opted to use a black binding post where a red one should have gone in the +5V terminal. That didn't look good, so this time around I found an online supplier and exactly what I needed.
I had also previously broken a blade of the fan on my lab power supply. The fan was on top as there was no space left inside the unit. However, I didn't have extra screws for the fan cover, so I left it off, and a fan blade got broken. For my second lab power supply, I reused four screws from the broken unit to attach the fan cover, which gave the supply a nice shiny finish.
Lessons learned from destroying and rebuilding my lab PSU:
Don't try to trick the overcurrent protection on an ATX PSU - it's there for a reason.
Source parts online - it's cheaper (sometimes free) and has better selection that RadioShack.
Using social connections to obtain unwanted (but useful) parts can pay off handsomely - the PSU I previously bought for $20 was free the second time around.
A very, very long time ago, I found a cool YouTube video (this is how everything starts, right?) showing a hydroxy torch melting stuff. Hydroxy torches are pretty neat, because they burn H2 and O2 gas cleanly, only producing water and a whole lot of heat. The heart of the hydroxy torch is a hydroxy generator, which electrolyzes water to split it into its constituent gases. I tried making one with hot glue and some scrap metal, and it failed about as badly as the word "hot glue" signifies. Hot glue is an inferior building material.
Years later, I was inspired to work on the project again when I saw a friend's hydroxy generator that he bought off eBay. I used the same scrap metal from the first generator design, but this time I used some proper plastic rods with spacers to assemble my electrolysis plates. This time, the design worked beautifully! I demonstrated that the generator worked by filling various containers with the explosive hydroxy gas and igniting them with a remote match. The video below has a compilation of some of the best explosions:
Regrettably, I seem to have burnt out my lab power supply (Experiment 7: ATX Computer Power Supply Conversion), so I'll have to make a new one and be more careful with my current consumption. Perhaps after that, I will use the hydroxy gas for a torch, but as of now, I am extremely happy with my newfound source of earth-shattering explosions. :)
Years and years ago, I decided I wanted to make thermite, so I tried to make a ball mill for producing aluminum powder, a key ingredient of most thermites. A ball mill powderizes materials by crushing them with the continual falling action of hard milling balls (in my case steel ball bearings). My first attempts to build a ball mill failed horribly. They were slow, finnicky, and didn't work at all. A couple months and a few YouTube videos later, I built one using a corded drill and some castor wheels, along with a metal container. The attachment of the drill to the container lid was so stressful that I ripped a perfect circle out of the container lid. I then switched to a plastic container with small bars on the inside to lift the balls up and send them crashing down on the aluminum foil inside. This worked... until the drill melted. No joke, the plastic on the drill melted and that was the end of the drill. Oops.
A few more months went by, and then I got a free dryer off Craigslist. The motor worked well, even though the first attempts to use it didn't. One time the motor spun so fast the ball mill container flew off toward the ceiling! I finally figured out a way to harness the speed of the motor with some belts and wheels to tame its ferocity. However, the ball mill still had the small bars on the inside. Most ball mills don't have these, for good reasons - they are loud and hard to clean (especially when attached with duct tape!). So, I took them off, and the balls in the mill proceeded to slide, rather than tumble. After a few more months of apathetically looking at the years-long failed project, I finally got the motivation to finish it and found a container that I hoped was the right size - the balls filled it approximately halfway up. To my extreme surprise, the ball mill worked! After years of dissapointment and failed prototypes, the mill jar finally opened to reveal ultra-fine aluminum powder! This is how many things in the inventing/experimenting business go. They take perseverance and dedication to finish and might not be immediately rewarding, but they will pay off if you finish strong and pull through until the end.
This has been the too-long story of how I built the ball mill to finally fulfill my dream of thermite. It takes about a week for it to turn foil shreds into fine powder. The aluminum powder produced has been confirmed to work in thermite. To sum up the mill's actual operation, I made the above video explaining how it works for milling aluminum... or anything else highly flammable. :)
“I have not failed. I've just found 10,000 ways that won't work.”
― Thomas A. Edison
A while ago, I found myself wanting a good way to make metal stamps for stamping element symbols into the various pieces of metal I have, in order to identify them when the time came to melt them into new and interesting objects. To accomplish this, I used a steel bolt and the electro-etching process to make a neat little stamp for hammering into metal. I first sanded the head of a bolt so it was flat and almost mirror-like in finish. Then, I applied masking tape and used a box cutter (along with a strong light) to painstakingly cut away the design, flipped in reverse. Since it's reversed, it will stamp out in the right direction. I then attached the bolt to my power supply's +12V and hooked another wire up to the ground terminal. I then placed the ground wire in the bottom of a dish with about 1/2" of strong salt water and put a cotton ball on top of it's exposed metal strands. I pressed the bolt head onto this lightly and waited about 10 minutes. What happens is the electricity erodes the exposed areas of the positive anode, producing iron oxide. This darkens the brine solution. After about 10 minutes of etching, I rinsed off the bolt and peeled off the tape. The places under the tape were still shiny, but the exposed areas had eroded away considerably and were deeper than the lettering, as seen above.
Finally, although it might not have been necessary, I hardened and tempered the stamp. This will prevent undue wear of the stamp, since it will undergo a lot of force throughout its life. I used a propane torch to heat the stamp head bright orange and then quickly dropped it in room-temperature water. To relieve the stresses built up by the sudden change in temperature, I tempered the stamp by heating its entirety to a blue color and then letting it cool in air. After testing on a strip of metal, I was quite pleased with the result. Honestly, I didn't think it would turn out this well.
This is what happens when I get bored on a summer afternoon. After being inspired by a recent Instructables project showing how to make a coin sorting machine, I built my own, changing a few things (for example, this sorts U.S. currency instead of Phillipine currency) and adding a silly name laser-engraved into the front.
The machine uses gravity and a slight backward tilt of the front window assembly to sort coins using specially-sized windows cut into the cardboard. The coins want to fall backwards, so when they get to the right window, they drop off the ramp, thus ensuring that they don't fall into a larger window farther down on the ramp.
I also engraved the name "Moolah Masta 3000" and some icons into the front of the sorter using my laser cutter. I have a category of posts related to building the laser cutter and fixing the issues that sprang up with its scavenged parts.
So far, the soin sorter hasn't every mis-sorted coins or gotten them awkwardly stuck. For having no moving parts, it works surprisingly well!
This was an especially fun experiment. After all, who can resist hand-staining chemicals that give off dense clouds of purple gas? Iodine is a fun chemical to have around, so I isolated some from sodium iodide.
To do this, I mixed the sodium iodide with just enough water to dissolve it all. I then dripped sulfuric acid (98%) in until it stopped reacting. Then, I mixed it well and let it sit for about 10 minutes. The iodine then precipitated out. Though I don't entirely understand the chemistry behind this, it relies mainly on the fact that sulfuric acid is both an acid and an oxidizing agent. Thus, the reaction also works with HCl and H2O2. NurdRage has good demonstrations of both the H2SO4 and HCl/H2O2 methods of isolating elemental iodine from alkali metal iodides.
I finished the experiment by setting the filtered iodine in a beaker and placing an Erlenmeyer flask filled with ice water on top of it. The Erlenmeyer flask fit snugly over the beaker, sealing it off. I placed the assembly on my hot plate and set it to high heat. The iodine sublimed and then condensed into really neat crystals which I stored in one of the ampules created in Experiment 28: DIY scientific ampoules. The ampule sealed up very nicely and will store the volatile chemical safely.
It was quite fun adding another element to my collection, and such an interesting, colorful one at that!
For a while, I've had the idea of building an arc furnace. When I saw The King of Random's video on building one using microwave parts, I knew it was time to act. Together, a friend and I successfully built an electric arc furnace.
This project has been fairly difficult and expensive, to be honest. At first, we got the wrong type of 8AWG wire (it was car audio wire instead of "normal" 8AWG stranded copper wire). It had very thick insulation and so I couldn't get as many turns into the transformer as the TKOR used. Thus, the furnace didn't really work. After that, we got some of the right wire and wound the transformers. This was an extremely difficult and unpleasant step. We could only fit 15 turns (rather than 18), and even at that, it was an awful experience putting the coil into the transformer. Fifteen turns seems to work fine, though.
After that was done, I had trouble getting lantern batteries for carbon electrodes. Though I will refrain from using foul language, I can only say that the recycling center I tried to get old lantern batteries from was uncooperative. My friend finally got some from a recycling center near him. We found that when extracting carbon rods from batteries, it is much easier if they are new. The manganese dioxide in old batteries becomes hard as a rock, making it difficult to get the rods out safely.
Another friend graciously gave me some alumina firebricks, which were easy to carve into the furnace. Rather than cutting two furnaces out of the brick like TKOR did, We cut the brick in half and cut the 2" hole in the middle of one half, effectively making a furnace with thicker walls. We used the other half as the lid. The idea was that once one part wears out, the roles can be switched. Another 2" hole can be cut in the lid to use as a furnace, and the bottom of the old furnace can be used as the new lid.
Having assembled all the arc furnace parts, we tested it on first zinc, then aluminum, then copper, and finally iron. The zinc melted but it also burned. This is typical of zinc. The aluminum melted nicely... too nicely. As I poured it into my aluminum muffin tin, it promptly melted right out onto the patio. I suppose I should have used steel to contain the brightly glowing aluminum.
In the video below, I used the furnace to melt copper scrap. This worked quite well. I found that the time it takes to melt the metal is longer than what TKOR says in his video (this is probably because I used larger amounts). When molten, the copper had an amazingly shiny glowing orange surface. It looked absolutely terrific. I used my foundry sand and a new, shorter casting flask to cast a neat little Cu tile for my element collection. After some cleaning up, it turned out very well.
Regrettably, after the copper melt, the furnace broke in half! There was only one crack, but it ran down the full furnace height, making it unsafe for use. I quickly turned the lid into a furnace and then used the broken furnace as the new lid. Once the swap was complete, I melted some iron/steel. It took about six minutes, and I should have gone longer, but the vice grip electrode holders were becoming too hot to hold, even with fireproof gloves. I tried to pour the molten iron into my Fe tile mold, but as I picked up the furnace, the radiant heat promptly burned me through the fireproof leather gloves! I only managed to get a tiny bit of iron into the mold, but I undoubtedly cast iron! For me, it was quite an achievement, given that I have only cast aluminum and copper until now. The rest of the iron froze in the furnace, so I will have to remelt it to get it out.
I am quite pleased with the results (Cu tile, achievement of casting iron), except for the broken furnace and the failed iron pour. I learned a few good lessons from the experience:
Cast in they daylight - the extreme light difference between the glowing iron and the evening darkness made it hard to see what I was doing when casting the iron.
Friends are always helpful in building complicated projects
Make some sort of handle for the electrode holders and the furnace - the heat that these parts radiate when casting iron is too much to safely handle, even with gloves
Don't try to scrape leftover metal out of the furnace. This could have been the reason the furnace broke (or it could have been thermal shock).
Though it was difficult at times, I have enjoyed this project immensely. There are few things as satisfying as casting glowing orange streams of molten iron. :)
