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Coilgun Rifle finished

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LAN_403

TheMerovingian

Mon Oct 30 2006, 08:39PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

This is my second coilgun. I work on it from 3 years ago (including concepting, designing, prototyping etc)

Specifications:
model: EMR0260S03HBP1TA
ammo model: 5,5x40SS
Stages: 3 (plus injector stage)
Type: Diagonal halfbridge of IGBT's and Ultrafast diodes, optically controlled with regulated pulse width
Type of loading: manual reloading with lever , 8 rounds magazine size
5mw laser pointer
charge time: (cold start 8 seconds, warm start 4 seconds)
power source 12V, 2,2AH ultracompact Sealed Lead-Acid battery
Extra functions:
1)Indication of projectile presence in the injector and prevents dryfires
2)Indication of charger state
3)three-function 10 led bargraph displaying cut-off voltage, actual average voltage, charging activated

Total energy: 260J @ 300V
Used energy per shot: 114V @ 300V
Exit kinetic energy: 6,5J
Exit speed: 41,5 m/s
Projectile mass: 7,4g
Projectile diameter: 5,5 mm
Overall efficiency: 5,8% (1,98% preacceleration injector stage, 7,07% first HB stage, 10,9% second, 10,4% third)
Kx = 14,60
Ko (taylor stopping power) = 0,256
1/14 th of the 9mm parabellum stopping power (3,5 points taylor)

As you can see the halfbridge has high efficiencies in the latter stages (also it can be tuned for velocity or efficiency, i searched a compromise on the pulse width)

All this using a conducting barrel and projectile and with no external iron.
I think that using the halfbridge topology together with controlled pulsetime, non-conducting barrel, external iron will rise the overall efficiency to higher values, at the cost of complexity though

...

Tue Oct 31 2006, 01:33AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Impressive!

Seems like you could beef up the charger a little? That gell cel should put at least 5A for short periods of time, 300J should not take more than 3-5 seconds (depending on if charger is constant power or constant current)

It is a shame more pople aren't into coilguns, some really nice work has been made by the few people that are willing to put time into it.

TheMerovingian

Tue Oct 31 2006, 02:05PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

At 5A the battery voltage will drop, possibly causing undervoltage lockout on the driver board.

this way it is safe and works well (the charger can be left turned on during firing)

Tue Oct 31 2006, 04:31PM

Registered Member #85 Joined: Thu Feb 09 2006, 01:22PM
Location:
Posts: 21

Indeed very impressive. Respect, i like it very much. It has the efficiency of my big unportable CG and looks like my portable CG. (i need to post them on this forum in near future.)
I love the halfbridge topology, it has only cost me 6 igbts untill now. R.I.P
I hope you have not suffered lots of igbt failures. BTW, how high is the peak current that you make those igbts switch off?

TheMerovingian

Tue Oct 31 2006, 08:39PM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

I had a lot of igbt and driver ic failtures. Just make sure that the igbt are properly driven, good gate drive design, and current limited in the 250-300A range (i used 0,7 mm wire to wind coils).

The igbt where the smallest problem, the worst was the lack of the driver ic's (IR2110) expensive and hard to find.

FastMHz

Tue Oct 31 2006, 09:11PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Very nice - I especially like the enclosure...

phil

Fri Nov 03 2006, 04:21AM

Registered Member #314 Joined: Mon Mar 13 2006, 03:12AM
Location:
Posts: 52

Wow, verry nice work. I like your warning labels

Quantum Singularity

Sun Nov 12 2006, 05:22AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

Nice!

But isnt it more like a Coilgun Pistol? Not really a rifle depending on your definition I suppose. Good work.

Simon

Sun Nov 12 2006, 09:28PM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Quantum Singularity wrote ...

But isnt it more like a Coilgun Pistol? Not really a rifle depending on your definition I suppose.

To be a true rifle it would need a rifled (threaded) barrel. I'm not sure if anyone's done this - it would be very complicated in DIY.

TheMerovingian

Thu Nov 16 2006, 10:13AM

Registered Member #14 Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383

I'm not going to waste my precious joules for a rifled barrel

. At this power levels the accuracy is affected most by the gravity

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