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Idea for a coil gun

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Ash Small

Fri Apr 10 2015, 11:28AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I assume there may be some losses from stray capacitance and leakage inductance, but this can be minimized through the usual procedures.

Gregary Boyles

Fri Apr 10 2015, 12:31PM

Registered Member #9039 Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117

Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.

I believe that not magnetic metals are fired from a coil gun by induction.

It is very well done.

DerAlbi

Fri Apr 10 2015, 12:40PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

i would use a rubber band instead. that could shoot 10 coins at once with more power

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Fri Apr 10 2015, 01:14PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

DerAlbi wrote ...

You get Iron-powder from ebay in various particle sizes. Just make sure its not iron-oxide. I am sure the supply will be even better using ebay.COM, instead of ebay.DE (in my case).. But yeah.. it doesnt hurt to try of course, but it hurts to be disapointed and waste time for something that has no chance of success.

I just felt like i could share my results...
success would be.. dependable on what you actually want

for me Âµr=4 (and for coilgun applications in general) is pretty useless.

Yes, "It doesn't hurt to try" I agree with you there. AND, as you say: to be disappointed may hurt, but that's how the learning and experience process works--Don't let it beat you just because you stumbled and it hurt a tiny bit. One NEEDS this if he is serious about learning, feeling, and creating new/unique methods in the application! Believe me, they are right there. {voice of experience

} However you are dead-wrong calling this a waste of time and stating that there is no chance of success. If nothing else, other worthwhile discoveries will emerge--most likely new EPA-forum related processes that can grow exponentially for your process. For now put aside that "ur=4" bump, DON'T give up, and MOVE on. If you are are really serious and have the drive, it is amazing what will emerge! You CAN and SHOULD share your results--they are most welcome and will not go overlooked.

DerAlbi

Fri Apr 10 2015, 02:10PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

Hmmh. But when you learn from failure that physics dictates the failure then there cant emerge much from anyone else, since the pricipal is prooven wrong;-) I see no one who got better than Âµr = 10 and even this result is extremely doubtfull. (since the measurement is not that easy)
If it was so easy with resing and ironpowder, then more people would do it. And industry would for sure not rely on a technique which involves extremely expensive casts that withstand the pressures and forces involved in makeing iron-powder-cores.
In the end.. if these experiments take away your time and money which you could have spent to build maybe an IGBT-halfbridge... i just strongly advise against following dead ends.

Ash Small

Fri Apr 10 2015, 02:54PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

You could use commercial iron powder cores and grind them to shape, you can even stick them together with epoxy (araldite).

Gregary Boyles

Fri Apr 10 2015, 05:00PM

Registered Member #9039 Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117

DerAlbi wrote ...

i would use a rubber band instead. that could shoot 10 coins at once with more power

Well it is cool if your only about having a bit of fun with the concept rather than to trying to produce a device that can penetrate plate steel or what ever.

BigBad

Sat Apr 11 2015, 07:54PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Gregary Boyles wrote ...

I was reading about how air core coils are very inefficient at transferring energy from the current to the projectile.

They're inefficient at low speeds, but at high speeds they become very efficient. Most people never get anywhere near fast enough.

Edit: even if you get this to work, the projectile if it is ferrous it is magnetised by the acceleration process and will be attracted laterally to the magnetic bore, and your projectile pretty much definitely will jam.

edit2:

Gregary Boyles wrote ...

Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.

I believe that not magnetic metals are fired from a coil gun by induction.

It is very well done.

Gregary Boyles

Sun Apr 12 2015, 02:30AM

Registered Member #9039 Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117

What would you guys consider is the minimum voltage for one of these?

I have been considering one that charges at 30-40V using 50V electrolytic capacitors which are easy to come by in discarded hifiis etc

Or one that charges at 100V or so using the 400V capacitors from tv circuit boards.

Or are these types of capacitors unsuited for a coil gun?

DerAlbi

Sun Apr 12 2015, 09:39AM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

That really depends on what you want.. if you try

having a bit of fun with the concept rather than to trying to produce a device that can penetrate plate steel or what ever

then a batterypack and a mosfet will do fine.

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