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starting a 6000J coilgun need a little help

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Metal Magic

Sun Dec 16 2007, 01:31AM

Registered Member #1177 Joined: Sat Dec 15 2007, 08:19AM
Location: A state bigger then texas
Posts: 3

here is ware i stand i have

(12) 6300mfd 400 volt 500 Joules 3X6 caps

(1) 750 AMP 600 VOLT SCR's Igt:150ma Vgt: 3.0V Vf (on): 1.5V-HOCKEY PUCK 1.65"

(2) 750 AMP 1600 VOLT SCR {stats same as SCR above}

(1) 800V 0.1amp power supply

(2) 1/4 POUND 12 GAUGE MAGNET WIRE

(1) 1/2 POUND 12 GAUGE MAGNET WIRE

and some basic electronic stuff

i plan to use 4 caps per stage and to rig the caps up in series 2 to each
to give me 800V per 2 caps any ideas if the SCR's can take the abuse
also whats all this stuff about safety diodes
i plan to make this gun portable also i would be happy whith at least
3% efficiency any coilgun vets wana help me out a little i will be glad
to put your name on the gun

something quick i whiped up in paint finished it should look more like a rocket launcher
made out of duct metal

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TheMerovingian

Sun Dec 16 2007, 11:33PM

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

First you need to ball park some basic calculations dependind on a chosen projectile such as pulse lenght versus speed and then decide R and L of the coils: this is very important since you decide to build a free running coilgun (no turning off). You have also to decide the wire gauge, barrel material and barrel diameter. If you are interested you can play with my simple simulator just to ballpark the values, make sure that you have visual basic runtime libraries
]1197848009_14_FT36028_coilgun_simulator_eng3- 00.zip[/file]

Metal Magic

Sun Dec 16 2007, 11:49PM

Registered Member #1177 Joined: Sat Dec 15 2007, 08:19AM
Location: A state bigger then texas
Posts: 3

Thanks i was looking for a calculator like that

anyone know if those SCR's can handle the abuse
also will a simple trigger coil work to trigger the SCR's

Slava

Sat Jan 12 2008, 03:00AM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

Try evacuating the barrel with a pump, and placing a thin cover slip from a microscope at the tip... it will give you much better efficiency.

Logan Kennedy

Sat Jan 12 2008, 04:11AM

Registered Member #1103 Joined: Mon Nov 05 2007, 06:02PM
Location: Houston
Posts: 80

What an interesting idea Slava. I've been looking for ways to increase the efficiency of coilguns. Do you have any more ideas?

Metal Magic: It's tough to tell if the SCR's will be able to handle the abuse. First you need to know the approximate resistance of the coils, and then you can calculate peak current. There are many variables, and without some basic measurements it's tough to deduce much of anything.

I will say that at glance the SCR's look a little weak if you plan on using four capacitors per stage. That's 2KJ per stage man! At roughly 800A if you plan on using 1ohm coils.

Another issue is the portability of this thing. How much does each capacitor weight? That's 12 capacitors at roughly 350 grams (just a guess) - that equals over 8 pounds for just the capacitors. Not to mention you also need an appropriate battery to charge the capacitors. Look into the LIPOLY technology, it's expensive, but you might be able to save some weight.

Jasonr

Sat Jan 12 2008, 03:38PM

Registered Member #167 Joined: Mon Feb 13 2006, 06:41PM
Location: Waterloo, WI
Posts: 54

Do you have better specs on the SCRs? Such as what is the I2T spec for the scr over 10mS this is really how much the scr can handle peak current.
also if you only have a few of these SCR I would make sure to protect them with flyback diodes across the SCR and across the coil. diodes are cheap compared to SCR's

this is a good place to look around
http://www.anothercoilgunsite.com/nf-portable-news.htm

looks like a fun project, have to started to lash anything up? better pictures?

Logan Kennedy

Sat Jan 12 2008, 03:52PM

Registered Member #1103 Joined: Mon Nov 05 2007, 06:02PM
Location: Houston
Posts: 80

Jasonr wrote ...
also if you only have a few of these SCR I would make sure to protect them with flyback diodes across the SCR and across the coil. diodes are cheap compared to SCR's

This should be a given regardless of the amount of SCR's available. It's the straight forward, smart thing to do.

Barry

Mon Jan 14 2008, 06:39AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

Jasonr wrote ...

also if you only have a few of these SCR I would make sure to protect them with flyback diodes across the SCR and across the coil. diodes are cheap compared to SCR's

I don't think an SCR needs a flyback diode for protection. The SCR is basically a four-layer diode to begin with. Now, the flyback diodes will definitely protect your electrolytic capacitors from reverse voltage -- it's always nice to get more than one shot from expensive capacitors. Not to mention that it's considered impolite to leak acid from a handheld gun.

Cheers, Barry
All those that believe in telekinesis, raise my right hand.

Electroholic

Tue Jan 15 2008, 02:30AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

Free wheel diode at just the coil and cap should do the job. Big ones next to the coil, and probably a 5408 accross each cap. Caps will fail long before you over volt

Lithium polymer batteries are good, only if you are sure what you are doing. I would just stick with a few packs of SubC racing packs.

For a gun this size, go look at anothercoilguns coil cannon. Most powerful multi stage gun ive seen. Very bare bone design, but it works.

If this is your first gun, good luck.

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