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Hybrid Coil Concept

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LAN_403

Maxwell

Tue Dec 18 2012, 04:13AM

Registered Member #8497 Joined: Tue Dec 04 2012, 06:24PM
Location:
Posts: 74

I have no documentation or pictures of my idea, so you'll have to bear with me whilst I attempt to describe it.

From a traditional basic CG system, there are 3 components: Capacitor, Switch, Coil.

Say now, that the coil has contacts at the very beginning of the wrapping, the very middle of the wrapping, and the end of the wrap - something like this:

||>->->->->->->->->||Layer 4 ----------Terminal Contact B
||<-<-<-<-<-<-<-<-<||Layer 3
||>->->->->->->->->||Layer 2 ----------Terminal Contact X
||<-<-<-<-<-<-<-<-<||Layer 1 ----------Terminal Contact A
------------------------------------Barrel
----- -------------------------------Barrel
||<-<-<-<-<-<-<-<-<||Layer 1
||>->->->->->->->->||Layer 2
||<-<-<-<-<-<-<-<-<||Layer 3
||>->->->->->->->->||Layer 4

Terminals A and B would be your traditional CG wrapping start and end points.
Terminal X is 'exactly' halfway through the length of the winding.

In this setup, the coil would conduct current (discharging the capacitor with IGBT/SCR) until the projectile has passed thru the center of the coil. At this point, a second SCR (think half-bridge / energy recovery systems) opens at terminal X leading to the positive post of a stageII capacitor.

I don't know how to model a non-ideal inductor such as this in any computer simulation software.

Maxwell.

Yandersen

Tue Dec 18 2012, 11:32AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

And this is easier than just using non-polar caps?
And why to start from the middle of the coil (X) instead of the normal end (B)?
Pretty crazy. I doubt this has any benefits.

Maxwell

Tue Dec 18 2012, 06:36PM

Registered Member #8497 Joined: Tue Dec 04 2012, 06:24PM
Location:
Posts: 74

Could the magnetic field collapse inwardly once Contact X is shorted to ground - Dividing the coil much like a voltage divider.

Yandersen

Tue Dec 18 2012, 09:51PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

I don't know. Think energy-preservation-wise...

You know what? No matter which kind of woodoo you will try to do out of a single coil, many small coils operating in a simple way will still perform better - guaranteed. So it is better to concentrate on switching mechanism between coils rather than fetishing around single coil. Just stuck with the best coil shape (length=inner diameter, outer =3*inner diameter) and go ahead increasing the number of coils. If/when room-temp superconductors will be invented, coils will turn into single-layer coils, but until then solution is found already.

To achieve the highest efficiency possible, coilgun must be composed of many small coils located as close to each other as possible, which are turned on and off as fast as possible, maintaining a constant current and returning unused energy back into source when turned off. Projectile must be as short as possible (I found that length less than diameter is technically hard to move through the barrel).

The coilgun of my dream is a cap-driven halfbridge with current control and optical triggering via optosensor wires going through the holes radially drilled in the iron washers separating each of two adjacent coils. I don't think any non-standard coil magic can turn a coilgun into something more efficient as the one roughly described above.

Yanom

Wed Dec 19 2012, 02:38AM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
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Posts: 158

Yandersen wrote ...

And this is easier than just using non-polar caps?

presumably it's price-related issues. Nonpolar caps are at least 4 times as expensive as standard polar electrolytics.

Yandersen

Wed Dec 19 2012, 04:01AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

If you buy from chinese on e-bay, you can get electrolithics many times cheaper. What about characteristics? ESR, ESL, lifetime, ripple current, repolarization capability, maximum voltage, e.t.c. The ONLY benefit of electrolitics is higher energy density. But comparing the efficiency of transfer of that energy to the coil during the shot... Non-polars are just born for coilgun. If you need 1kJ to accelerate a piece of nail to 30m/s with electrolithics, than compare it with 54J for 54m/s given by 3pc of my non-polars. Those cost me $60. How much you would spend on 1kJ of electrolithics?

Turkey9

Wed Dec 19 2012, 05:00AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I hear you mention your coilgun built with non-polars, do you think you could start a thread with pictures and detailed description? Such a high performing device would be a great asset for teaching coilgun theory around here.

Yandersen

Wed Dec 19 2012, 09:52PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Haha! Not yet. I'm working on portable 16-stages version of this with 11mm caliber to make it look presentable. The unfinished 6-stage is about to be disassembled as it holds half of the caps I have in it. The main reason is that I've discovered ideal coil shape too late, and the iron fender washers of required dimensions for 9.4mm caliber do not exist, while for 11mm I'm going to use 32mm external to 12.7mm internal diameters thick iron washers which are the main part of the separative coil blocks. I will also change the shape of the projectile from plain cylinder to something more bullet-looking - this requires to rebuild all coils anyway. The flaw of the current small version is a weak 5-min-made case which is falling apart, so increase in power will brake it. Another not-constructive-related reason is that efficiency is promising to be slightly better. Probably, I will try to redesign the charger to give it more power. Give me a pot of mana and time.
Here is the last picture of the first recuperational coilgun prototype for the history:

Yanom

Wed Dec 19 2012, 11:25PM

Registered Member #4659 Joined: Sun Apr 29 2012, 06:14PM
Location:
Posts: 158

right now I'm working on a coilgun that doesn't have any capacitors at all.
It just hooks up to the power supply.
Also it doesn't use semiconductors! Each stage is triggered by a mechanical switch that protrudes into the barrel.

Yandersen

Thu Dec 20 2012, 02:25AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Good start, but don't expect high speed from this, even if energized from car battery.

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