SpudFiles

that was most definitely not an ETG. Unless DYI changed his bank since i saw it on 4hv, 400 joules input will not do that.
I say ETC....or C.

You underestimate my ETG, rp181. I used 450J input, which gives me around 100J output. Just because most amateur ETGs are useless doesn't mean they all are.

I dont think you can even shoot through a dime with a .22lr, so i dont think you could do it with an airsoft gun.

.22 LR rounds range from 140J to 280J. This was roughly 100J. Double the speed, and it would have a very good chance of making a hole.

Ragnarok is right, a heavier BB would help. I suggest a .20g or .25g BB (I think .25g is the highest they go but you'd have to order it online most likely).

Dimes are so thin that even if you shot it with a 30.06, you would just bend it. I dont have factual information, but thats my guess.

You would have to have something that supported all around it, basically a custom vise that is made specifically for holding a dime. if you did that, then yes, i would bet you could do it. other wise, my guess is you are just going to bend it and have some really nice dings, but no penetration.


read the 4th post on this forum- http://www.firearmstalk.com/forums/f48/ ... oins-2273/

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SpudBlaster15 wrote:

hi wrote:You would have to have something that supported all around it, basically a custom vise that is made specifically for holding a dime.

I have something like that in mind, and a >1.5km/s 0.2g airsoft round should have a fairly good chance of achieving some penetration.

your talking about something that shoots almost a mile per second... I am a pretty big gun nut and i can honestly say that i dont know of a single commercially available rifle out there that shoots at 5000 fps... im not saying that it can't be done, but if solid propellants have trouble with that, then i haven't a clue what you are going to do.

its an awesome goal and i say go for it, but i don't think that you can do it without solid propellants. whatever you do, be safe and don't kill yourself, or anyone else for that matter.

pm gippeto remeber he made the near speed of sound coaxil that shot airsoft bbs jack take out your high velocity burst disk launcher but use your hpa tank instead of 400psi with a pump

twizi wrote:pm gippeto remeber he made the near speed of sound coaxil that shot airsoft bbs jack take out your high velocity burst disk launcher but use your hpa tank instead of 400psi with a pump

You do understand what dyi fired this from don't you? Something that can reach significantly higher velocity than any pneumatic here. They won't make it.

I do have a 1 km/s design on the drawing boards which uses "legit" spudgun fuels, or a more powerful one that doesn't.

DYI: I was overestimating, I was assuming 200 joules output
But then again, i am not very good at matching energy up to damage.
I forget, are you using electrolytic capacitors, or a pulse capacitor? what is the voltage?

inonickname wrote:You do understand what dyi fired this from don't you? Something that can reach significantly higher velocity than any pneumatic here. They won't make it..

Nope. Even with the improvements...even if I tried helium...at dangerous pressures...still wouldn't be in the running.

That IS impressive damage for a plastic bb .... period.

Good job DYI.

Ragnarok wrote:

DYI wrote:Predictably, it didn't go through.

Well then, it clearly wasn't going fast enough.

(Actually, I think the problem is more lack of mass and excess of velocity. Heavier BBs would likely help)

+1 , try 0.36 grams BBs...

hi wrote:I'm not saying that it can't be done, but if solid propellants have trouble with that, then I haven't a clue what you are going to do.

Solid propellants are limited - they can only contain so much energy for their mass, and can therefore only get so hot, limiting their speed of sound (and thus potential maximum velocity) to values in the range of 1200 to 1500 m/s.
Propellants for APFSDS rounds tend to be better, but still limited under 2000 m/s.

The problem is, what solid propellants produce on burning is a heavy and relatively cool gas, so it hasn't got much specific energy.

DYI is using a plasma, with a much higher specific energy, and thus with a much higher speed of sound. Plasmas can have temperatures of millions of degrees C (indeed, temperatures of billions of C have been achieved) - but for practical purposes here, we're talking about a few tens of thousands degrees C.
This places it as about an order of magnitude hotter than propane flames, and thus with a speed of sound into multiple kilometres a second.

So, I'd stress that the 5000 fps you think is "trouble" is actually nowhere near any kind of limit.

Light gas guns are good for 10 km/s (~33,000 fps) and if that's not enough, electromagnetic means have been used for up to 42 km/s (~138,000 fps).
Admittedly, neither by amateurs, but solid propellants are nowhere near the king of the velocity world.

hi wrote:You would have to have something that supported all around it, basically a custom vise that is made specifically for holding a dime. if you did that, then yes, i would bet you could do it. other wise, my guess is you are just going to bend it and have some really nice dings, but no penetration.

The description on one of the photobucket pictures details how I did it. For higher impact energies, that assembly could have been made with a thicker washer and clamped in a vise. With higher impact speeds, I expect that the hole would be made before the dime could deform very much.

hi wrote: your talking about something that shoots almost a mile per second... I am a pretty big gun nut and i can honestly say that i dont know of a single commercially available rifle out there that shoots at 5000 fps... im not saying that it can't be done, but if solid propellants have trouble with that, then i haven't a clue what you are going to do.

Direct your attention toward the Rheinmetall 120mm L/55. Smaller rifles shoot much heavier projectiles in relation to their bore, cutting down the muzzle speeds they achieve. We see that in spudding as well - cast lead rounds are much more common for plinkers than they are for 3" bore pneumatics. Also, there are alternative methods of using chemical energy for propulsion...
Speaking of which, one new rule: the airsoft round must be shot at the dime, not the other way around

A 0.20g BB at 1.5km/s would have a very good chance at making a hole.

The capacitor used for my shot was 16uF, charged to 7.5kV.

Edit:

Ragnarok wrote:DYI is using a plasma, with a much higher specific energy, and thus with a much higher speed of sound. Plasmas can have temperatures of millions of degrees C (indeed, temperatures of billions of C have been achieved) - but for practical purposes here, we're talking about a few tens of thousands degrees C.
This places it as about an order of magnitude hotter than propane flames, and thus with a speed of sound into multiple kilometres a second.

That's not quite correct - I'm using plasma to vaporise a propellant (water, in this case). The resulting propellant gas (a mixture containing mostly steam, dihydrogen, and dioxygen) is much cooler than the initial plasma. The best estimate I have of the SOS in the chamber is between 1600m/s (worst case - mostly steam, 4000K) and 4000m/s (complete dissociation into atomic species, 8000K, definitely not happening here), probably closer to 1600. It is, of course, much easier to vary the SOS in an ETG than it is in any other gas expansion based launcher - use less propellant, and it gets hotter.

julktyl wrote:Ragnarok is right, a heavier BB would help. I suggest a .20g or .25g BB (I think .25g is the highest they go but you'd have to order it online most likely).

Incorrect, they go from .12 to the metal .8's. But you will typically see .12, .2,.23,.25,.27 bioval,.29 sgm,.3,.33,.36,.40, and .43

julktyl wrote:Ragnarok is right, a heavier BB would help. I suggest a .20g or .25g BB (I think .25g is the highest they go but you'd have to order it online most likely).

Sandman is right.
I've got .34 BB's (plastic, biodegradable) and .89 BB's (steel).

I think that hitting the coin in the center is very important, aswell as the backstop.
There should be a 8mm hole in a steel backstop right behind the coin, so that a circle can get punched out easier. (If you want to go through)

psycix wrote: I've got .34 BB's (plastic, biodegradable) and .89 BB's (steel).

I think that hitting the coin in the center is very important, aswell as the backstop.
There should be a 8mm hole in a steel backstop right behind the coin, so that a circle can get punched out easier. (If you want to go through)

First, allow me to remind you that this challenge requires you to use plastic BBs. Playing airsoft with steel BBs would be interesting, but you'd need some rather overpowered guns to launch such heavy rounds...

I was sure I'd explained on the Photobucket page how I'd held the coin, but I can't seem to find it. I used a 1/2" washer to sit the dime on, backed by a magnetron magnet (disk shaped with hole through middle) to hold it all together and add some mass. Clamping the magnet in a vise is possible, but likely unnecessary, as the impacting round has very little momentum compared to the mass of the target. For those with non-ferromagnetic coins, it wouldn't be too hard to make something similar to a pipe flange as a clamp.