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Forums
4hv.org :: Forums :: Electromagnetic Projectile Accelerators
<< Previous thread | Next thread >>   

What's going on with this coilgun??

Author Post
Signification
Tue Feb 23 2016, 03:06PM Print View
Registered Member #54278
Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 285
This coilgun puzzles me. but it shoots through steel There are a few youtube videos here:

It's called the YAK 6-stage. For one thing, with the coils placed back-to-back, I would think suckback would be a huge problem since the projectiles are the length of each coil! Also, IMHO, the position of the projectile down the barrel is educated guesswork...way too many variables, esp since different projectiles are used! And the SCR's just stay on?? etc, etc,

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DerAlbi
Tue Feb 23 2016, 07:15PM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 499
Hoooooooly fuck. Watching this video just hurts.
On 4:02 he states that due to the 450V and the 0.2Ohm resistance his peak current is 2.25kA. Then he tells us the "power is I*E", so 450*2.25kA. Indicating his capacitor is at full charge while he actually has reached his peak current achieved by purely resistive means. nobel prize incomming. Well.. 1MegaWatt sound impressive.... yeah and dont forget the 6 coils... 6 Meagwatts then. well a little less "maybe 5 or so"

And people let me tell you, SCRs prevent the electromagnetic force to get back into the electonics!

He puts a resistor in series with the reverse protection diode rendering it useless.

And reverse charge does not hurt the capacitros if its short time!!! Yeah.. right. Not.

His 11g projectiles at 78m/s give only 34J. Sooo in the video title says... "Worlds fastest coilgun". Impressive, I would dare to call that "humble". And yeah he needs a Website to calculate the energy.

And to everybody who want to build a coilgun.. just remember: "there is actually no calculation in building one of these [coilguns]"
Yeah... such thinking yields 6MW.

And yeaaaah!! What coilgun community needs is a power supply!! Didnt he mention it would blow without a resistor at the output?? Like the video to get the schematic! Yeah thats what the community needs! Bad designs!

Such an IDIOT...

Dont bother. Not worth commenting. Might be a highly skilled troll or a poorely skilled gardener.

To comment on your questions:
The suckback is basically his method of keeping the projectile in sync with his pulses. If the projectile is too fast (due to lucky conditions) its slowed down again and accelerated normaly by the next stage. A fixed (and too slow) switching is a very relieable method of producing very accurate and repeatable projectile speeds.
And yes the SCRs just stay on (thats what they do!!). He times his stages by giving each coil its individual capacitor thus timing.

I do not understand why you waste your time with watching those kinds of videos. There is nothing to gain.. just brain to be lost.

Dont get me wrong here... his build is ok and the 4%eff is ok for the topology.. but does the blind really need to start explaining colors?
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Signification
Sat Feb 27 2016, 01:38PM
Registered Member #54278
Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 285
DerAlbi wrote ...


I do not understand why you waste your time with watching those kinds of videos. There is nothing to gain.. just brain to be lost.

Dont get me wrong here... his build is ok and the 4%eff is ok for the topology.. but does the blind really need to start explaining colors?


@Albi:
If you ran across this title, wouldn't you watch it?--of course you would...and it wouldn't be a -waste of time-!!
"Brain loss?" no way!! Don't say that.

My original intention was to start a discussion of the many peculiarities of this design, discussing errors and their solutions, generating new ideas and methods from it's oddity's--after all it got impressive results (the most I've seen in areas). This yields "Brain GAIN". Many of the things you bring up, I spotted instantly...in it's entirety, it's curious. Please don't go the route of killing the thread by a response with massive text (...thought you didn't like that anyway ) that prematurely "summarizes it all". I have a good deal of experience in coilguns, you have more, and others still more than that. I believe this design is worth a healthy thread.
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DerAlbi
Sat Feb 27 2016, 04:06PM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 499
So what in particular do you like to dicuss?

Common Mistake: The resistor in series with the diode?
Bad Design: The coil geometry
Bad Design: The projectile geometry and material
Bad Design: No projectile sensing
Good Design: No coil spacing
Good Design: Reliable Timing due to the "computer" he used
Design consequences: still low efficiency for 6 stages.

What exactly is the design aspect you like in particular? 35J projectile energy is not bad, but not unseen on youtube. 4% efficiency is also not unseen (and actually pretty lame for 6 stages). Its nothing more than 6 times the SCR design... so what is new or inventive besides his idiotic desciption of his lack of understanding what he actually built?
Everything he did (wrong) is discussed over and over again like the optimal coil shape, capacitor charging and discharge timing and also the back-emf snubbing. Do i miss an aspect that would not be allready repeated 100 times? Its a basic SCR design.
The multiple things in this design and your request to only write a short text is quite an interesting challange. Hopefully someone will serve your needs Maybe you start with your version of productive commenting for a healthy thread so that people actually have something to discuss
The actual things you asked i tried to answer but it wasnt enough, so sry

imho what is most worthy of discussing is the ethical dilema humanity faces by such videos where just bullshit is taught and the unknowing kids just believe whatever they hear thus leading to a generation that will inherit even the most basic mistakes leading to even less understanding and starting a reverse evolution. This easy conent is simply more appealing than the correct stuff. Deleting such bullshit is clearly a violation of free speech and the beginning of censorship, but letting it sit there and poisoning the interested is equally bad. So couse of action would be?
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hen918
Sat Feb 27 2016, 05:41PM
Registered Member #11591
Joined: Wed Mar 20 2013, 08:20PM
Location: Alfreton, UK
Posts: 383
DerAlbi wrote ...

...
Deleting such bullshit is clearly a violation of free speech and the beginning of censorship, but letting it sit there and poisoning the interested is equally bad. So couse of action would be?


Pointing out the faults so the interested can learn from others' (many) mistakes?
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dexter
Sat Feb 27 2016, 06:13PM
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 163
it all comes down to the purpose of the device...
since this is basically a toy it doesn't rely matter how efficient it is nor how right is build
applying DerAlbi logic to other sections of this forum: a SSTC is not worth building because A DRSSTC is the best option

these simple designs don't cost much and have a wide tolerance to mistakes and are a great tool for learning
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DerAlbi
Sat Feb 27 2016, 07:03PM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 499
Hmmh both interesting statements
Dexter, i think there is a little missunderstanding: building something is allways great! Its totally fine - and its the way to learn stuff. My problem with the video is that he opened his mouth, not that he used his hands.

Hen: I agree with you in principal but then i think about how this guy build the gun and what resources he might have used. He obviously is in some kind of forum and he also searched around youtube a lot so he is confident he made "the best thing ever".
Yet his research lead him to his kind of thinking and to those results - meaning repeating errors other unknowing people explain on youtube.. Actually he studied it so well that he thinks he knows it all good enough to teach. If corrections in the comments of his resources would have helped, the video were different.
Strange.
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Saz43
Sat Feb 27 2016, 07:08PM
Registered Member #1525
Joined: Mon Jun 09 2008, 12:16AM
Location: America
Posts: 294
DerAlbi wrote ...

Watching this video just hurts.
On 4:02 he states that due to the 450V and the 0.2Ohm resistance his peak current is 2.25kA. Then he tells us the "power is I*E", so 450*2.25kA. Indicating his capacitor is at full charge while he actually has reached his peak current achieved by purely resistive means. nobel prize incomming. Well.. 1MegaWatt sound impressive.... yeah and dont forget the 6 coils... 6 Meagwatts then. well a little less "maybe 5 or so"



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Karmaslap
Tue Mar 29 2016, 11:55PM
Registered Member #58215
Joined: Wed Dec 30 2015, 11:27AM
Location: Boise, Idaho
Posts: 62
I made a couple of replies to this guys videos with questions/suggestions. Really minor stuff. He somehow has the electronics expertise to make all this, but doesn't understand the theory or do any research of other people's designs or work.
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DerAlbi
Wed Mar 30 2016, 06:10AM
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 499
You dont need any "electronics expertise" for building a coilgun with the SCR design. Its all based on 'monkey sees, monkey does' and it pretty much always gives you some results.
Its not a bad thing.. everybody starts that way (we are still monkeys ) but the question is how you develop from this point on.
Many dont.
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Karmaslap
Fri Apr 01 2016, 06:02AM
Registered Member #58215
Joined: Wed Dec 30 2015, 11:27AM
Location: Boise, Idaho
Posts: 62
No, but most people don't know how to use a fluke/oscilloscope and wouldn't think of using one or have one around to use.
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