SpudFiles

I've done a lot of work on this launcher over the break, on seals, burst disks, sabot catching, and the vacuum system for the barrel (which now works perfectly). The first shot of the break was fired today, using an optimized UHMWPE sabot weighing 3.66g to carry a 1/4" hardened steel ball (the mass of the total assembly was 4.72g).


The round is sitting on the burst disk used for this shot, 0.024" thick 7068 aluminum.

The predicted muzzle speed was 1700m/s, and based on previous results with WARTL, I didn't expect it to come close to penetrating the 3/8" steel plate. You can imagine my surprise when this happened:





The round in the hole in the second picture is for size comparison, the small crater on the bottom right is from a WARTL shot in 2011 with the same projectile.

The sabot catcher wasn't very well thought out, and all that UHMW spraying out to the sides destroyed part of the barrel vacuum assembly:





That groove wasn't there before, and the sealing face used to be perpendicular to the axis of the threads. On the plus side, only a few milligram scale fragments of the sabot escaped the catcher, and only two of the parts I accidentally destroyed will take long to replace. My estimate of ten shots this break may have been somewhat optimistic

Oh, and for anyone who's counting, that's the fastest shot fired by a hybrid on Spudfiles by a margin of about 700m/s

DYI wrote:The predicted muzzle speed was 1700m/s, and based on previous results with WARTL, I didn't expect it to come close to penetrating. You can imagine my surprise when this happened:

Do you think the new sabot had something to do with it or that you just underestimated its penetrative capabilities?

I remember a couple of shots with a hybrid a few years ago where one round failed to penetrate and then a second, identical, round with a slightly different sabot penetrated the target, my backstop, and my garage door

Do you think the new sabot had something to do with it or that you just underestimated its penetrative capabilities?

The WARTL shot I was basing my estimate on must have been slower than I initially thought. It wasn't measured directly (it also, obviously, didn't need a sabot, as WARTL is 1/4" bore). The sabot can't affect the ability of the round to penetrate when none of it comes in contact with the target. What you saw on the hybrid shot you mentioned was the penetrator "falling" through the sabot on the first shot, and thus going slower than it would have if the sabot had worked properly. I had this happen with a sabot round I fired back in 2013. That was when I started doing stress analysis of my sabot designs.

It's also worth mentioning that the prediction for this shot was done using GALE, so while it can be somewhat inaccurate due to chemical kinetics and 2D effects in the tapered section, it can't be very far off. WARTL is *much* more difficult to model, so I can't offer any comparison on that front yet.

Very impressive work..

what is the target made of?
Looks like concrete but that would shatter...

what is the target made of?

The target is 3/8" steel plate.

Oh...aha..Riiiight.......


I thought it was -like- something really impressive..

but it's just..a....3/8...steel plate...

Cough..gasp....ughhhhhh...choke...

Excuse my lack of knowledge but how does this compare to conventional weapons as far as penetration? For example if an Ak47 or US equivalent was fired at the steel plate what would the result be? Or what weapon does this sort of penetration compare to?

By the way awesome launcher you have made!!!

Excuse my lack of knowledge but how does this compare to conventional weapons as far as penetration? For example if an Ak47 or US equivalent was fired at the steel plate what would the result be? Or what weapon does this sort of penetration compare to?

This plate was mild steel, and thus not directly comparable on most armor penetration numbers (it's much weaker than, say, AR500 armor plate). The penetration capability of this 1/4" steel bearing ball would be similar to that of .308 FMJ. However, that's just this one shot, which was aiming to test the high speed and barrel vacuum capabilities moreso than achieve high penetration. The ball only carried 20% of the kinetic energy of the shot, the rest being in the sabot, which was deliberately stopped.

An AK-47 with AP rounds could shoot through this plate (with a projectile about ten times heavier but 850m/s slower), with FMJ rounds it would probably be close.

Thanks, that's impressive especially considering you say only 20% of the energy was in the ball. Its in a completely different league to my pneumatic which I thought was fun! Well done it is superb. Don't think I would be safe with it, although my neighbors aernt close I would worry about sending a round though their house or something worse!

Here's the video for the first shot, where I fired a 1/4" bearing ball through a 3/8" mild steel plate:



I decided to do a better job on the barrel end assembly after breaking the first one, and came up with this:





The sabot catcher now has a 1" deep, 1" diameter hole to prevent the side spray from damaging the vacuum assembly, and looks like this when inserted:



There was a second shot after repairing the damage from the first, using a magnesium sabot carrying a 3/8" steel bearing ball, with the total assembly having a mass of 7.5g for a predicted speed of 1440m/s. The target (a 1" thick steel section) was positioned 2m from the muzzle, and I missed More accurately, I mostly missed.



The ball sat in a 3/8" diameter central hole in the sabot. When the sabot hit the catcher it would necessarily do so (slightly) unevenly. This caused deflection of the projectile as it left the sabot, which was sufficient to cause it to graze the inside wall of the 7/16" hole through the catcher, resulting in the ball breaking up and impacting over an area about 4" across, which only partially overlapped the target. The fragments that did hit the target were at the edge of the spread, and caused damage to about 1/4" deep. The rest impacted the concrete backstop (4" thick solid block), knocking off a spray of fragments and detaching a 10kg chunk from one corner. The video isn't worth watching. The impact of the magnesium sabot with the catcher at 1400m/s melts or boils around 10% of the sabot's mass, and converts another half or so into a spray of hot dust, all of which ignites in the air as it leaves the catcher through the central hole. The result is 14 frames of total whiteout, preventing anything interesting from being recorded. Modifying the sabot design to prevent this projectile breakup from happening again is a simple matter, and will be done for the next shot. I'm also working on methods to (partially) contain the muzzle flash, resulting in better video and allowing me to chrony the shots. The Chrony should work up to 2000m/s, a performance claim I hope to put to the test this May

Sweet fancy Moses

Fork, when i thought i was about to reach the mighty DYI on muzzle speed with an electrothermal accelerator i find this, something that put a big grin on my face, seeing DYI still with his crazy projects is something really pleasing, i wrote on my first message how noticed lack of important advancements on this years i was out of this community but i am glad to be wrong. My "horse spudgun project" consisted of a 30mm 180cm long barrel 1.2L chamber volume at 30X fueled with methane helium-oxygen mix but looks like it will need a complete revamp on the scale to be able to share the laurels of spuding gods, i remember when i asked with my old account if it was possible to build a "meteorite" gun using the aforementioned gas mix at 200X on a bigger launcher, i got some replies that kindly modeled my gun on HGDT.

Keep the good work DYI! some day i will try to beat your records if life doesn't get in the middle like happened before, also i couldn't help but notice the lack of any restraint mechanism on those tanks be careful!.

Hey Equus. It's good to see someone else involved in the high speed side of things. I'd be interested in seeing the gun used to make the crater in your profile picture, especially given my soft spot for ETGs. My crazy projects continue apace, but they don't fall within the scope of this forum at the moment. I was originally planning to spend a few weeks this summer better characterizing the performance of Stage1 and implementing some ease of use improvements, but something more interesting came up. I did at least manage to get the tanks tied down a bit better

Also, I don't think I ever saw the methane-helium-oxygen cannon you mentioned. Did you post it here? I was originally planning something similar, but hydrogen was considerably easier for me to acquire than methane (and I couldn't acquire helium at all, due to the shortage). Two tanks also simplifies the plumbing. Still, the spectre of pumping and transferring hydrogen at 9000psi is daunting to say the least.

Thanks, I really appreciate that you have interest in my ETG *fangirls*, i made a post about it http://www.spudfiles.com/hybrid-cannons ... ml#p379639 . It is very ghetto so it will be nothing compared to what you make. Yes its true i've also seen very few people is interested in building launchers capable of surpassing 1000m/s routinely. also is good to see you are still with your projects even if they are stagnant, i wonder what could be

Considering hypervelocity guns and the problems you had with the sabot catcher, i found a paper mentioning the use of a tapered sabot catcher which use the deformation of the sabot to augment the speed of the gun, i think you could try to see if it works for you, regarding this i am thinking in using a small steel block with a 6mm cavity filled with water with a taper at the end with a small hole to see if i can launch really small projectiles at extreme velocities or at least a jet of water.

Here is my post i mentioned i did some time ago with another account http://www.spudfiles.com/spud-cannon-re ... 24357.html i was offered the oportunity of requesting custom gas mixes so i could ask for a Oxigen-Helium mix in a tank, i thought of using that mix as i was still believing in the horror stories of hydrogen being "hghly explosivw" but i think using Hydrogen-Oxygen is relatively safe and not only more convenient but offers more performance.


When i open a high pressure thank i get nervous (2500psi), dealing with 9000psi! wow that isn't something to take lightly it would suck if a hose or a fitting breaks, you want to get more nervous? stick a thermocouple to the hose and see the temperature rise when you open the thank. . You mentioned pumping i only seen gas tanks reaching 4500psi i am curious to know what kind of pump do you have to reach 9000psi.

Edit: Link to post about my ETG added.
Cheers in the name of hypervelocity!

...i found a paper mentioning the use of a tapered sabot catcher which use the deformation of the sabot to augment the speed of the gun...

I found it too. The trouble I'm having is actually measuring the speed to start with The fuel mix is rich enough that the exhaust gas becomes a 2m diameter fireball when it exits the barrel. I either need to hide the flash to successfully use a shooting Chrony, or build my own wire-break system using an Arduino or similar (this is a much easier problem than measuring speed for electric guns). I just might get around to doing the first one this summer, as it will only require perhaps two days of construction, and a minimal budget.

...i was still believing in the horror stories of hydrogen being "hghly explosivw"...

Well, in fairness, hydrogen/oxygen mixes are extremely sensitive primary explosives with short DDT runup distances. DDT avoidance is paramount in any gun using oxygen-enriched mixes, and hydrogen mixes are some of the worst in that regard.

You mentioned pumping i only seen gas tanks reaching 4500psi i am curious to know what kind of pump do you have to reach 9000psi.

A gas booster, like this one. They're compressed air drive pumps that take pressurized gas at the inlet and increase the pressure by a factor of up to 20 (for single stage boosters).