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Halo Style 2 stage COILGUN

AnselmoFanZero

AnselmoFanZero

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Sounds good.

Cant tell you the exact values...for that you would have to measure the velocity. 40m/s for example would mean: 4000cm per second...pulsduration 0.4ms
4000m/s x 0.0004s = 1.6cm or 16mm
Your slug would travel 16mm within duration of the pulse...only an example.
You should put your contacts as close as possible to the coil!
 





millirad

millirad

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OK, I see what you mean. The contacts need to fire on time and not prematurely so they must be close to the coil. I should have said that I will start building the second stage tomorrow, because I will need to get some more caps first. :)
 
AnselmoFanZero

AnselmoFanZero

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Dont hurry. As long as it looks cool and pierces a car in the end ^^

You have to place the contacts right at the coil entrance (depending on your projectile....if the tip is very flat-angled, you can put it maybe 5mm away from the entrance) to avoid wasting energy.
Hard to explain...if you would have a longer pulse and increase distance between contacts and coil, you would waste the first few % of the pulse...know what I mean?
 
millirad

millirad

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Yes, contacts can be 5mm away from the entrance of the second coil and give enough time for the firing coil to develop full power. ;-) OK we will see what happens tomorrow.
 
AnselmoFanZero

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The projetile must have its head in the coil already when the puls fires...thats what I meant. Then you will use the full duration of acceleration.
 
millirad

millirad

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So there must also be enough delay, so that the coil doesn't fire "before" the projectile has entered the coil's entrance. If the coil fires too soon then some percentage of the power is lost.
 
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AnselmoFanZero

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Thats exactly what I am talking about...thats why you have to put the contacts as close to the coil as possible. My projectile is lurking into the coil...maybe 5mm of the tip...works fine.
On the other hand you have to limit pulse-duration, because when the projectile just passes the middle of the coil, speed will decrease, caused by the suck-back-effect / neg. pulse!
 
millirad

millirad

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So after a complete rebuild of the single stage my coil gun is functioning very well for a single stage. The contact lifted on the photo flash board for the capacitor bank and couldn't be fixed so I had to go to another board. The prototype configuration is very crude at the moment but I had to prove that my components had not failed. I will hunt down some more caps for the second stage tomorrow.
 
AnselmoFanZero

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Cool.
Now you know how to do it and the second stage shouldnt be a problem...
Be prepared for moaaar power ^^
 
millirad

millirad

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Yes, I want mooaaarrrr POWER. :D My brother-in-law is an elevator controls engineer and wants to see my coil gun. He will move me ahead and add scr's or igbt's to the design, which ever is more available. They sometimes use igbt's on elevator circuits where he works. :)
 
AnselmoFanZero

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IGBTs would fit a low volt coilgun...I believe.

Ask for SCRs...

How many J energy-storage has stage 1 again?
 
AnselmoFanZero

AnselmoFanZero

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Keep your hands off those puk-SCRs...you have to make a heavy sandwhich to make them work...

The TO94 type looks good. 200V may not be enough though.
Ebay is a pretty good source too btw.
 
StridAst

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curious, what do you mean by "heavy sandwich" to make the puck type scrs work? I've heard they are the only real thing that works to switch larger capacitor banks. (been reading up on railguns too, but haven't found anything on how to implement this type of SCR)
 
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StridAst

StridAst

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ah ic. good to know. If I get a coilgun or two up and working, I might try for a railgun after, but that's a distant hypothetical situation.
 
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