Crazy 10kJ coilgun in youtube
Wizzup, Sun Feb 24 2013, 04:52PMI found this video in youtube:
In the end of the video I understand that it says that it has 4% effiency, 4% out of 10kJ is 400J of kinetic energy! It also seems like it is just one coil and it mentions aluminum in the text so I would guess that this is induction based, but in the schematic in the video the coil looks very much like "normal" coil so what do you think? Is there any people here from Poland that could translate the texts for us who dont speak Polish? I would like to know more about the coil's structure and what kind of capacitors they use. There is also some footage of it firing, it goes through those wooden plates like its nothing.
EDIT: I just noticed that if you look at the coil before the shooting you can actually see the projectile there, so it is for sure inductance based. Would be interesting to know the velocity of the projectile and how much it weights.
Re: Crazy 10kJ coilgun in youtube
Maxwell, Tue Feb 26 2013, 02:25AM
I noticed they're using what looks to be a thyratron - which I believe is regulated (in the U.S.) much as nuclear weapons are - as they can be used to detonate nuclear explosions.
Maxwell, Tue Feb 26 2013, 02:25AM
I noticed they're using what looks to be a thyratron - which I believe is regulated (in the U.S.) much as nuclear weapons are - as they can be used to detonate nuclear explosions.
Re: Crazy 10kJ coilgun in youtube
Electroholic, Tue Feb 26 2013, 04:39AM
That's a trigatron, a triggered sparkgap in other words. Pressurized with argon I think he mentioned.
Quite impressive I must say.
Electroholic, Tue Feb 26 2013, 04:39AM
That's a trigatron, a triggered sparkgap in other words. Pressurized with argon I think he mentioned.
Quite impressive I must say.
Re: Crazy 10kJ coilgun in youtube
..., Tue Feb 26 2013, 04:42AM
It looks like a trigatron (which admittedly is very similar to a thyratron), most likely built in house by the looks of it.
I think you are right that it is induction based, although the coil geometry seems odd for a normal induction launcher, but I do not think there would be any way to get that class of performance from a single stage 'normal' coilgun.
..., Tue Feb 26 2013, 04:42AM
It looks like a trigatron (which admittedly is very similar to a thyratron), most likely built in house by the looks of it.
I think you are right that it is induction based, although the coil geometry seems odd for a normal induction launcher, but I do not think there would be any way to get that class of performance from a single stage 'normal' coilgun.
Re: Crazy 10kJ coilgun in youtube
DerAlbi, Tue Feb 26 2013, 02:14PM
May i ask what you think is the limiting factor?
and... Maxwell... seriously...
DerAlbi, Tue Feb 26 2013, 02:14PM
May i ask what you think is the limiting factor?
and... Maxwell... seriously...
Re: Crazy 10kJ coilgun in youtube
Adrenaline, Tue Feb 26 2013, 04:05PM
I believe you are thinking of the Krytron.
The coil 'geometry' is odd, I wonder if it is just showing the position of the projectile WRT the center of the solenoid coil. The coil just being a regular solenoid.
Adrenaline, Tue Feb 26 2013, 04:05PM
Maxwell wrote ...
I noticed they're using what looks to be a thyratron - which I believe is regulated (in the U.S.) much as nuclear weapons are - as they can be used to detonate nuclear explosions.
I noticed they're using what looks to be a thyratron - which I believe is regulated (in the U.S.) much as nuclear weapons are - as they can be used to detonate nuclear explosions.
I believe you are thinking of the Krytron.
The coil 'geometry' is odd, I wonder if it is just showing the position of the projectile WRT the center of the solenoid coil. The coil just being a regular solenoid.
Re: Crazy 10kJ coilgun in youtube
..., Tue Feb 26 2013, 05:18PM
Assume a 100g projectile, means it is accelerated to 100m/s (projectile probably weighs less than that)
Acceleration length looks to be about .02 meters, assuming constant acceleration the projectile is in the coil for 400us.
This means that all 10kj of energy needs to be dissipated in well under 1ms, which is in agreement with their claim of a having on the order of 10^6 amps of current.
Assume the caps are 10kv, 200uf (wild guess, but I see some maxwell pulse caps under the table), the series inductance of the whole mess has to on the order of 10uH, which would be consistent with an air core coil about the size of theirs, but if you put a lump of metal in it the inductance is going to go up significantly, making it hard to keep the pulse width short enough while still generating a large B-field in the coil. This is why there are few successful single stage coil guns with more than a few KJ of energy.
So- I conclude that either they are purposefully running the projectile in the 'very' saturated regime to keep the inductance down (which is hard to believe given their decent 4% efficiency), or they are using a non-ferrous projectile which they are accelerating purely using induction.
..., Tue Feb 26 2013, 05:18PM
DerAlbi wrote ...
May i ask what you think is the limiting factor?
May i ask what you think is the limiting factor?
Assume a 100g projectile, means it is accelerated to 100m/s (projectile probably weighs less than that)
Acceleration length looks to be about .02 meters, assuming constant acceleration the projectile is in the coil for 400us.
This means that all 10kj of energy needs to be dissipated in well under 1ms, which is in agreement with their claim of a having on the order of 10^6 amps of current.
Assume the caps are 10kv, 200uf (wild guess, but I see some maxwell pulse caps under the table), the series inductance of the whole mess has to on the order of 10uH, which would be consistent with an air core coil about the size of theirs, but if you put a lump of metal in it the inductance is going to go up significantly, making it hard to keep the pulse width short enough while still generating a large B-field in the coil. This is why there are few successful single stage coil guns with more than a few KJ of energy.
So- I conclude that either they are purposefully running the projectile in the 'very' saturated regime to keep the inductance down (which is hard to believe given their decent 4% efficiency), or they are using a non-ferrous projectile which they are accelerating purely using induction.
Re: Crazy 10kJ coilgun in youtube
MrFlatox, Tue Feb 26 2013, 10:37PM
You can use non-ferrous material in a coilgun ??
MrFlatox, Tue Feb 26 2013, 10:37PM
You can use non-ferrous material in a coilgun ??
Re: Crazy 10kJ coilgun in youtube
DerAlbi, Wed Feb 27 2013, 12:03AM
... May i ask why smaller coil guns work then? they suffer from the same effects - these scale with the projectile size.
Or can you explain why the mentioned things dont effect smaller guns?
Current rise time can be influenced by voltage - not only by inductance - and Amps*turns matter sooo... decreasing inductance is not the best thing.
Where would you set the theoretical limits and why? Sry, i realy dont see your point
DerAlbi, Wed Feb 27 2013, 12:03AM
... May i ask why smaller coil guns work then? they suffer from the same effects - these scale with the projectile size.
Or can you explain why the mentioned things dont effect smaller guns?
Current rise time can be influenced by voltage - not only by inductance - and Amps*turns matter sooo... decreasing inductance is not the best thing.
Where would you set the theoretical limits and why? Sry, i realy dont see your point
Re: Crazy 10kJ coilgun in youtube
Yandersen, Wed Feb 27 2013, 12:06AM
Surely it is an induction launcher - regular coilguns are not for such energies (at least single staged ones) and that's why thyrasmg is used - no semiconductor exists that can handle megaamps.
The efficiency of regular coilgun drops after saturation, but induction launcher increases efficiency with power. The explanation is following: before saturation force is proportional to the square of the current (for both coilgun types) - the same as heat losses. So increasing energy lowers the time it takes for projectile to leave the coil, so the higher the energy, the less the pulse time, so efficiency rises. But regular coilgun experiences saturation after some energy limit and force becomes proportional to the current almost linearly (while induction launcher always has force proportional to the square of the current), and as result efficiency starts to lower with increase of energy. At some point low initial efficiency of induction launcher becomes larger than a regular coilgun's efficiency. In addition, with very short pulse times repulsion from eddy currents in a regular coilgun with solid iron projectile may decrease the force dramatically.
I was thinking about making an induction launcher shooting pennys - two flat spiral coils on top of each other and a penny in the gap between those coils, slightly pushed out of center of those coils. But so far my experiments with induction give me the way too low initial efficiencies, and I'm not a fan of high power.
Yandersen, Wed Feb 27 2013, 12:06AM
Surely it is an induction launcher - regular coilguns are not for such energies (at least single staged ones) and that's why thyrasmg is used - no semiconductor exists that can handle megaamps.
The efficiency of regular coilgun drops after saturation, but induction launcher increases efficiency with power. The explanation is following: before saturation force is proportional to the square of the current (for both coilgun types) - the same as heat losses. So increasing energy lowers the time it takes for projectile to leave the coil, so the higher the energy, the less the pulse time, so efficiency rises. But regular coilgun experiences saturation after some energy limit and force becomes proportional to the current almost linearly (while induction launcher always has force proportional to the square of the current), and as result efficiency starts to lower with increase of energy. At some point low initial efficiency of induction launcher becomes larger than a regular coilgun's efficiency. In addition, with very short pulse times repulsion from eddy currents in a regular coilgun with solid iron projectile may decrease the force dramatically.
I was thinking about making an induction launcher shooting pennys - two flat spiral coils on top of each other and a penny in the gap between those coils, slightly pushed out of center of those coils. But so far my experiments with induction give me the way too low initial efficiencies, and I'm not a fan of high power.
Re: Crazy 10kJ coilgun in youtube
Maxwell, Wed Feb 27 2013, 04:19AM
Yep. That's what I was recalling. They all sound the same, anyways.
Maxwell, Wed Feb 27 2013, 04:19AM
Adrenaline wrote ...
I believe you are thinking of the Krytron.
I believe you are thinking of the Krytron.
Yep. That's what I was recalling. They all sound the same, anyways.
Print this page