Lane's .308 Lightning Build (log)

[Lane]

Found this video by accident. It's not really a rail gun, it is in fact what appears to be a multi-stage reluctance launcher. 

The only place I could find discussion of the mystery polish video in the first post of this thread was here: https://4hv.org/e107_plugins/forum/forum_viewtopic.php?id=151070 Nobody there seemed to have any idea what was going on either; or how it could function.

So; I ran some more tests with the early parts I had on hand. So far; nothing groundbreaking. Though; the trigatron fires reliably, and drains the capacitor bank almost completely. Still experimenting with projectile insertion distance. It can make a huge difference in a single stage setup. There is again some metal spray on the glass tube after operation; and it might even show glass cracking after multiple uses. Think it might be wise to order thicker wall tubing for the next set of parts. Changing electrode material (to stainless steel maybe?) might also make that better. I'm not seeing any spray from the small wires on the HV trigger. Can't tell if the solder is helpful or not. Maybe it melts instead of sprays? I can make more of these at will with parts on hand; so it's not an issue to experiment further.

Next up is to mess with other projectile materials. Aluminum isn't even special; interestingly GMX projectiles made of gilding metal have almost the same electrical resistance as aluminum. Nothing close to pure copper, but worth testing as an analog to the aluminum projectile used in the "unknown" video.

Just upgraded the test capacitors from 2Series4Parallel setup at 600V (shown in the picture), to 3Series3Parallel at 900V. From here on out; it's going to be a fun game chasing safe working voltages. The next bank will probably be around 2kV. Then 4kV; and whatever I feel comfortable with beyond that. At some point; it becomes difficult to keep things from randomly arcing over in air, or to the end user. These capacitors are actually rated at 330V; but I have trouble charging up that last little bit, so I'm derating them in use for the time being. I can actually go a bit further derating max voltage and get much faster charging times as well.

Shouldn't take too long to solder up a bunch of larger capacitor banks. Anticipate breaking the 2kV and 4kV barriers in the next few days. At some point I'll be able to start looking at projectile speed as well, and begin to consider specific limitations. So far so good though; and it's really neat to watch the "pop" inside the glass tube. I have been thinking about doping the inside of the glass with corona dope, which is a purple color. The portable build is going to require light shielding as an option for sure. It's blindingly bright with an air filled tube. Not yet sure how that changes if I switch to pure argon. 

[jtallen83]

18 hours ago, Lane said:

Found this video by accident.

Just getting ready to post that, Kentucky took one on the low setting 

I'm not gonna pretend to understand any of this but I'm paying attention for sure.

[DNP]

15 hours ago, jtallen83 said:

 

I'm not gonna pretend to understand any of this but I'm paying attention for sure.

Right there with you….this is awesome. 

[Lane]

Killed my first trigatron tube with about 20 shots. It appears the metal spray on the glass is a problem, but after doing a little bit of searching I found a material that might be better than copper. Tungsten copper is apparently used in spark switch electrodes, and isn't terribly expense in 1/4" rods. 

Soldered up a lot of capacitors and found a potential error in my earlier line of thinking. I was doing napkin math and kept getting strange numbers; only once I "fixed" that problem did I realize I might have an efficiency issue or worse.

That lead to me refactoring for a second day of soldering capacitors together. This time they are left to right backwards. That will give me the ability to bend if I need to make dramatic changes to my build here... Not a big deal; and I'm glad I caught it early on. 

I had the opportunity to speak with someone about my endeavors in this project. Discussing the original polish video briefly lead me to a potential "discovery" about that setup. It remains to be tested experimentally; but the above changes to the capacitor banks (left to right backwards) are a result of that conversation. 

The only other thing I have on my mind at this point is blowing up the cheap trigatron tubes. Literally. I'm worried about shattered glass or worse on a first firing when I upgrade to these larger capacitor banks. I also need a faster way to charge them; but for the time being I'm still covered if I take time between tests. From here on out experimental shots will happen outdoors. Might even wear some leather and a welding mask if it is looking risky. The flash inside the tube was already bright enough to make a dark shade useful.

I'll check back in within a week. It's going to be fun testing these out; but I'm getting more nervous now. Just one swipe of bare skin on bare wires could be a problem. Every move around this needs to be calculated and methodical. Don't trip and fall face first into a charged capacitor bank.

[Lane]

New 12ga wire coil wound on a carbon fiber barrel; just for testing. It's cheap, and using parts on hand. I was able to move the red coil to an acrylic barrel to see if there is any issue with eddy currents in CF. Might as well wind a few more coils if I'm going to start leveling up the power. Since the projectile is a set length; I can wind a 15ga coil from magnet wire I have; that will take some time.

Those spark pictures are actually difficult to capture. I don't have a system for it; just keep trying. That particular installation makes a lot of ozone, and a sucking sound; but it's an early prototype of stainless steel screw electrodes.

On the road to other materials if need be. AA battery holders are going to be garbage in terms of actual electrical contacts. Will need a slim nut, and a ring terminal on the screws to make that functional in real world testing. It's quite loose in a AA battery holder too which might be resolved with thicker glass tubing; or maybe larger I.D. too. Perhaps even better inside something much larger, like a 35mm film can sized container. They could last a lot longer if they didn't spackle the inside of the glass tube with metal particles. 

This particular tigatron model is up for testing with a shorter glass tube; among others.

Quite frankly the old style with copper electrodes worked GREAT for the first 5 firings or so. They are really cheap, and quick to make. Just hoping for something a bit longer lasting as I step up the power. The next set of tests I will paint on some corona dope inside both ends of the glass tube leaving an inspection window in the middle. I'd rather not dope the whole thing if I don't need to.

Can't lie. The sound of those huge ignition sparks (~20mm gap) really do get me going. The simple design will also allow it to just run the ignition HV generator on trigger pull. So with an empty capacitor bank, or a filled bank out of circuit; one can set off the loud lightning sounds "to make sure the gun is working". The spark picture in the middle is just that... An ignition spark. The full load flash that follows the ignition lightning is blindingly bright.

[jtallen83]

On 9/5/2021 at 3:17 AM, Lane said:

Tried to break some glass tubes to make trigatron test units. But so far I've not done well at scoring the tubes

PM an address, I actually ran across both inside and outside glass tubing cutters I knew I had, just need set screws in depth stops. Somebody that may use them needs these before I lose track of them again, you are the first person I ever heard of that had a use!

[Lane]

Wow; that's a super generous offer! It is funny; I just sat down to mess with this project again. Figured I could knock out another bag of capacitors while awaiting tungsten copper electrodes to show up in the mail tomorrow. Very curious how that material is going to machine. Almost dead set on drilling out the center of one electrode in each unit for the trigger wire... And of course the shape of the electrode "tip" should be rounded as well. 

I have setup my laser to cut borosilicate glass tubing, and need to get back to that at least to see how much I can improve on the process. I was doing six pretty slow rotations before, and it almost fell apart. I think if I do about 8 rotations it should cut the glass clean through. That doesn't mean it was the best method; but it sure did turn some heads in the laser cutting community when I mentioned it worked at all. 

That said; the tubing is actually kind of garbage in uniformity to begin with. Running it on the rotary has never allowed me to spin it on axis. The laser cuts as such, end up looking like garbage (sort of wide, and they might always look really bad). I expected the laser to simply score it, and was blown away when it actually fell apart at the cut line. I'm planning to run another batch quick before the electrodes arrive so I have something to play with. The only thing I'm concerned about still is the I.D. of the glass tubing. I may be well served to use the electrode diameter with a multiplier to build a better trigger tube (perhaps glass tubing with an I.D. 3 or 4x the electrode diameter). 

All of that remains to be seen once I test this new tungsten copper material. It's supposed to be ideal for spark gap switching. So... Mildly excited to see how much less it sprays all over the glass when the gas ionizes in the tube. Mmmm; plasma. 

Sadly. I misplaced my test projectile and haven't had the heart to make another one. That's because I already know it's not an ideal projectile in any way except one. The one being; it matches the weight of a 7.62x39 projectile; 123 grains, which is a useful benchmark. I'll find it, or grudgingly make a new one. 

@jtallen83I'll probably still take you up on your offer. But I do want to see how tomorrow's testing works out as a matter of proof. I do expect to be making a lot of replacement glass tubes if they continue to get spattered on with repeated firings. Even copper electrodes seem to last just fine; but the glass getting dirty was causing malfunction over time.

Images: prepping the leads, and laying out piles of 7 for more strings/blocks to be soldered together again.

[Lane]

Short update... They sent me pure tungsten rods instead of the copper-tungsten I had ordered. Double checked; I ordered the correct item. And yet the packing slip said drawn tungsten instead.

It was pretty clear to see before I even looked at the packing slip. They are grey metal colored, without any hint of pink. Also weighed them; not even close to what they should be (too heavy). I've made contact about the issue, but have yet to hear back. 

*** Heard back today; they are sending me the copper-tungsten I ordered, and apparently don't want the pure tungsten back. Not really sure what to do with it off hand, but maybe something will come up down the road. I will probably try to do some cold working on a piece, but from what I gather that might be slow going at best. It has a melting point similar to platinum, so it shouldn't be impossible to weld. 

Finished soldering together another bank of capacitors, and started re-working the previous blocks. I simply wanted to add 1 more capacitor to each of those parallel strips. The hardest part of that was removing the conservative amount of hot glue I had used to keep them together. Might have actually been easier if I had used an excess of hot glue instead.

[Lane]

Tungsten-copper rods showed up for the spark gap electrodes. They look a little strange, but it isn't a material I work with regularly; so I can't say if it is normal or not. The centers are pink enough, and I suspect they will work just fine for my needs (unless they need to be larger in diameter). Looking for my hacksaw at the moment.

Finished soldering up all but ten of the total quantity of capacitors I purchased for this project. Very much time to get serious with a few baseline tests; and then move forward with a larger testing system. 

Charged up a test bank to 2kV twice now; and let it bleed off slowly. Since I'm already in the middle of it; measuring the charge, as well as bleed-down time will give me some decent jumping off numbers. Once I get the whole thing wired up on terminal blocks, I'll be able to move things around and run ever increasing tests a lot faster. 

Still didn't get around to cutting more glass tube. The computer that runs that machine fell off the network apparently, and I have not yanked out the plug to reboot it yet (it is headless; no display). I'd feel better about a way to access it without just yanking the plug out... That said; I still don't have a repeatable process to do those jobs either. The first time I set one up, it was flying by the seat of my pants. I aimed it, and told it to draw a line 6x the circumference of the glass, and let it rip. 

Did hammer on some pure drawn tungsten rod... Should have trusted my gut. Never made a dent in the rod, and it shattered once I started getting into it. That was fun for a whole minute or two.

Feel like I might have done my homework on this one; as nothing has started on fire yet. A few steps later now, and I'm recharging a battery on an electric flyswatter that I used to charge my test capacitor bank. I used a good amount of that battery charge. Just need to scale up battery size, and the charging circuit (for speed); according to those metrics. 

There is just one more thing I didn't fully seat until now... I could in fact use all the SCRs to try and speed up the projectile pooped out by the trigatron accelerator. The fun part here would be making sure a timed approach could apply; and using the lower voltage DC battery power to make it happen. Maybe a stacked H-bridge, or something banging an induction drive would work. But that's all still a bit too far out... Only to say; I'm thinking about it, and getting ready to start looking at the other end of this problem. The stage two. Pictures incoming when I feel like setting up for all that. (still in the frazzled wiring stage at the moment).

[Lane]

Image update:

Series/Parallel capacitor bank charging up to 2,000V off a lithium battery powered electric flyswatter. Charge to just 2/3rds takes about 20 minutes, and kills the battery flat. Could get more speed with two; removing the bleed resistor would help as well.

ESR of the Series/Parallel capacitor bank.

ESR of the fully Parallel capacitor bank.

Fully parallel capacitor bank wired up. 

The full stack of 490 capacitors in small flat rate boxes. They don't quite fill them up; but that air gap at that top helps me feel better that they won't arc over. 

New parallel capacitor bank charger.

Showing 9V out of the set 12V... I'm drawing more current than I want to play with on my desk; but it can charge to 1/3rd voltage in just a few seconds (VERY fast). With unbound current supply, it could go a lot faster still. Simply trying not to start a fire yet.

Have tested the charging and bleed down of both capacitor banks. Just need to set them up side-by-side on the same coil and see which way works better in the real world. I can theorize all day long; but testing is what matters. Just about to clear off the laser for glass cutting. Last image is a drawing of the latest re-design of the trigatron tube. I found a fuse holder that looks like it will give me the best contact area on 1/4" tungsten copper rods. Even allows for a third electrode drilled into the end. The glass will be fatter than a standard fuse between clips; but the contacts will fit the clamp-in holders, and give me the best electrical contact I can find off hand for this scale of device. If the need to get larger; I'll refactor again as needed. Each short piece of tungsten copper will make 3 electrodes. Another reason for the evolution is that I haven't regularly exceeded about 10mm for the total spark gap. Shorter gaps (to a point) will make the triggering happen faster anyway.

[DNP]

I’m trying to absorb what I can. Electricity is an amazing thing and I wish I understood it better. Entertaining as hell to watch. Loving the progression of your project. 

[98Z5V]

On 11/2/2021 at 4:57 PM, Lane said:

 *** Heard back today; they are sending me the copper-tungsten I ordered, and apparently don't want the pure tungsten back. Not really sure what to do with it off hand, but maybe something will come up down the road.

 

If it was 1/2" diameter, that's buffer weights, right there.  If you could build a steel sleeve to accept that 1/4" up to 1/2", it's still buffer weights. 

[Lane]

On 11/9/2021 at 9:51 AM, DNP said:

Electricity is an amazing thing and I wish I understood it better.

Same here. That's why I'm doing this. Same reason I was doing this years ago when I was in school... Only; I understand a hair more now. 

At this point I'm able to start looking for points of friction in the system. One of the fist clues (and one I was guessing about a while back); is the reading on the series/parallel capacitor bank. I did my best to overcome all that from the start; but even still... I'm looking at a 93.633803% power on the series/parallel bank; compared to the full parallel set. I'm not willing to poop away 6.5% of my power just to be High Voltage. 

Again; there might be a good reason to do so; that's why I'm going to try it anyway.

Thought some people might like to see real progress. So here is a picture of tungsten-copper electrodes I cut with a hacksaw. Some of them a slightly filed clean; but I can't find a nice file. The closest "cut" is shown factory cut facing up. There's a weird "ring" on those; where it looks like tungsten migrated (heat related?).

Two more from a similar project. Cutting FR4 for the first time in a laser. The next few weren't nearly as rotten and burned. Figured out I had to start the cut with pulsed power, and then dig in once the cut line was made. Later cuts didn't look very much burned at all. I suspect these custom made circuit boards might turn up in this project at some point (FR4 is the back side of a single sided PCB (printed circuit board), or the center part of a double sided board. The fiberglass resin that acts as an insulator and makes the board's structure).

 

 

[Lane]

Why is this place so quiet lately? I hate to post progress when the news cycle is so slow... Maybe I should post more though. Hard to find primers and all that.

Had to clear this off my desk for a while. But just finished ordering all the rest of the parts give or take a few screws and whatnot. Needed a battery to supply huge currents. Check. More HV power supplies; Check two. 

Someone just ordered up a ring made of Element 75 (on the Periodic Table) the other day. No idea if I can make that happen. I will try though.

Once the packages arrive; it's game on again. Just programing up the lab radar, again (that's so annoying; someone should fix that firmware.... Please?).

[98Z5V]

38 minutes ago, Lane said:

Why is this place so quiet lately?

Busy, man, busy.  Always on the go, but check in everyday, and post what I can.  I read this thread everytime there's a new post.  

Next weekend is another shoot, locally.  The one last weekend, pistol heavy, was great.  Just always on the go, or reloading ammo...  

[sketch]

Always a lull during the end of year and holidays. We are here bro. 

[jtallen83]

On 12/4/2021 at 7:10 PM, Lane said:

Element 75

I caught something in the reading about it making a good electrical contact, third highest melting point of all the stable elements and the highest boiling temp. Looks like now's the time to play with that stuff, prices are down to $250 a troy ounce, measure twice  

[Lane]

On 12/7/2021 at 8:39 PM, jtallen83 said:

Looks like now's the time to play with that stuff

I've decided to dive in to that project for a bit. I really have no idea how it is going to work out; there are a lot of problems with trying to work with a molten metal at that temperature. It is not even entirely related to this project. But since I'm already trying; it might be a candidate for a test electrode moving forward.

More power supply modules, and a large battery showed up. I just need to start wiring up terminal blocks so I can mess with this in open form experimentally. 

One thing I had almost forgotten about here was a high voltage probe for a multimeter; probably oscilloscope too... I just ordered one the other night; so that should be here soon. With a 40kV max limit, I should be able to check the things that matter. These days I'm most worried about heat of the wires during discharge. Generally though; that does allow for higher electrical current flow, to a point... So it might be a blessing in disguise if I don't break any rules (i.e. start a wire fire).

[98Z5V]

21 hours ago, Lane said:

With a 40kV max limit,

DAMN!!!   

[Lane]

High voltage probe showed up. I measured a whole bunch of stuff I had laying around that I wasn't fully up to speed with yet. One of the lithium powered electric flyswatters tops out at 4,700V on a full charge; it sags as the battery voltage drops down to around 3,500V before it cuts off the power. The other one like it only peaks at 4,000V (ordered a 2-pack) which might be due to a manufacturing defect (I have already opened it up and found a pinched battery cable; a wire resistor). Those are working just fine for charging capacitor banks to a reasonably high voltage for testing. Might need another pair; but that's really cheap at this point. And they kill bugs. No reason not to get a few more.

The ignition modules in particular are going to need a bit more effort in that department. Those devices seem to start above 25kV. They "sing" and quickly start dropping in output voltage due to the resistance of the HV probe and probably wiring too; settling around 15kV. Still have another half dozen of them to test; and ideally try to get some handle on what the peak output voltage really is.... This is a big part of why I needed an HV probe; I knew the voltage was up there... I assume they can also be wired in series or parallel; but I haven't messed with that at all. Reality is they start WAY above even 40kV.... The only reason I see that low number is because of the resistance in the probe (and wires).

I still need to get back into the math to design a few second stage coils. Since I already purchased a bunch of silicon switches (SCRs) to dump capacitors. I might as well work out those details. Early on I bought a bunch of 10mm gapped IR triggers to work with sight holes, or acrylic barrel sections. If I don't blow anything up in the process, I could have a seven stage secondary that can run independent of the arc triggered initial acceleration. 

While I'm thinking about it; I might as well dig into a CAD drawing of the major elements. I've already drawn some of the difficult components. So it's just a matter of fleshing out the new details. Coil size is relatively static at this point; and none of them will change much in length or thickness.

Prototyping is hard. I got lost in the CAD drawing for a bit; and I'm still not back on track. Happens. Really should be using another 3D application once I make these parts. 

[Lane]

Sad to knock up my thread that had 69 replies; but... There's a new demolition ranch video. I really should dig out the build that I've had stashed away for a while. Everything is here to finish it; but I haven't started playing Tetris with the parts yet. 

Interesting that they call out the bull-pup design a bit after 5:30 in the video. My build started out as a slight one-up of the GR1 specs. Nice to see that in action here. But I also never planned to fire 50 cal projectiles (or full auto)... The new ArcFlash Labs offering is only 22 Cal. The EMG-01B which run $1,350 - https://arcflashlabs.com/product/emg-01b/

I'll be back sometime soon with a real update. But I welcome any thoughts that come from watching this Demolition Ranch video; or whatever else comes to mind. I could use a little kick to get this going again... Lots of new tech in the shop here; which will come to light as I get moving again. Mostly; metal cutting with a laser, but a bunch of new test equipment too; which I hope helps keep me on the safer side of this project. 

[Lane]

Hard to see in these images (use your imagination; the fins are in the tail); but a fin stabilized projectile could work well in a smooth barrel, and spin. I've had my eye on this since I put this project away the last time. A laser could easily make these directly; without the hassle of casting from 3d printed objects. 

Though; casting from 3d prints is fine just the same. Nothing to lose either way.

I watched the video again for myself. And this is the thing that stuck out the most in terms of things that need to be "fixed".

 

Edited May 21, 2022 by Lane

[Lane]

This has been distilling for a while. Something hit me while I was thinking about efficiency issues. What if you could fill the barrel with pure hydrogen? It's possible that the projectile could exit the barrel at 2x the speed in that case.

That's a bit difficult since hydrogen won't stay in the barrel for any length of time. But then I tried to calculate the volume of a barrel. A 0.308" barrel is only 0.0018 CF in volume (at 24"). It should be EASY to have that much H2 on hand very quickly if you can split some water. Already have electricity in the device.

Then; it begs the question... Can't you just ignite the H2 (and the otherwise useless O2) after the projectile is already going fast in a low friction gas filled barrel? Probably....

I bought a few barrels and all the extra parts for this build. I didn't realize it was going to go so deep. But; I already posted some of the H2O gas can videos. These should stick around... They do a slow-motion / high speed camera thing; listen for the "can" to fall in the end of the audio. 

Edited September 14, 2022 by Lane
audio 1

[Lane]

Been a while. I've be "slacking off" on this project; and some others. I do have some minor progress though. A CNC Unimat lathe is kicking out 5.56 monolithic copper 101 projectiles in twenty one minutes, twenty one seconds each. Not even highly optimized. 

Still having some issues with backlash and tool purity. But there is progress none the less.

I want to try my hand at some 308-ish; and maybe some others.... I'd love to model the 911 grain projectile sometime; but it will be a bit before I get my feeds and speeds right to get a good finish. No rush there. 

Finally of course; I will soon be making steel and aluminum projectiles for the electric project. 

[willbird]

I have never tried it yet but have always thought that a spring, or an air cylinder might work to help keep backlash in all one direction for light cuts anyway.