Magnet coil help (turns, gauge, for coilgun)

[supak111]

Whoops, my previsous calculation was off a bit. Four layers would use up on 120 inches of wire, not feet! It will take 19 layers and the outer diameter of the coil will be 3 inches.

You should start with the desired muzzle velocity. Then you can calculate the forces needed to to accelerate your projectile to that velocity. Then you should figure out how much force a given coil can impart. I don't think you are going to be able to calculate these, or find tables anywhere, so you are going to have to experiment. You are going to need equipment that will blow your budget before you even get started.

And, by the way, for this coil, the inducance is 3mH. This is means it will take about 10ms for the current to ramp up to 125A when supplied with 40V. Sort of makes 2000 shots per second a little difficult, doesn't it? Oh, I know, your 2000 shots per second is only on the bigger ship mounted gun. But the bigger gun will have much bigger coils with much more inductance. I think you are talking about many kilovolts to be able to turn these coils on and off in 1/2 msec. And now the insulation begins to be a problem. Do you see where this is going?

Bob

This one? I read it and asked a few questions after but we all skipped it.

I you guys said my battery will not do 125a at short circuit so say it does 50a at 40v, so what do I need to do to get my 3mH coil to ramp up to 50a in 1/2ms? Add Volts? Less turns or more tuns in a coil maybe? What? I'm here for suggestions and advice.

PS: I found a bunch of calculators and Volt will speed it up, or lowering mH of the coil will help but you guys already knew that

 

[(*steve*)]

I you guys said my battery will not do 125a at short circuit

No, we suggested it would do much more, and destroy the battery while it was doing it.

so say it does 50a at 40v, so what do I need to do to get my 3mH coil to ramp up to 50a in 1/2ms?

I think you'd need 300V to do that.

Add Volts? Less turns or more tuns in a coil maybe? What? I'm here for suggestions and advice.

or reduce the inductance by a factor of 7

 

[CocaCola]

This one? I read it and asked a few questions after but we all skipped it.

We all skipped it? Quite the contrary, it was supposed to ignite a light in your head most of us understood the issue quite well...

I you guys said my battery will not do 125a at short circuit

We never said that, we didn't elaborate for a reason (at least I didn't) it was to hopefully ignite a light in your head and give you something to explore... Did you research short circuit battery potential? Do you understand what it is?

Add Volts? Less turns or more tuns in a coil maybe? What? I'm here for suggestions and advice.

How much study have you done on the science of coils? Might be a good read if you are planing to continue making a coil gun... Just saying...

 

[(*steve*)]

I guess that professional inventors these days consider the need for actual understanding to be a superfluous liberal/conservative (strike out whichever does not apply) conspiracy theory.

 

[supak111]

My job isn't to build anything but to suggest ways to improve things before a final design. Engineers do the rest, people that went to school for it but don't have much creative/inventive of a mind. I don't do electrical improvement, but usually physical design improvements. That's what I'm trying to do here but unfortunately I first have to have a working coilgun before I can improve one. Believe me I've tired buying one from people who have a working one to save time. I'm sort of starting from the scratch in something I don't normal deal in at all, so please excuse most of my ignorance but I am trying. Its a lot to learn in a few weeks, 3 weeks ago I didn't know what a IGBT was so...

Here my question, if my coil isn't going to allow the current to rise past x amps, do I still have to worry about destroying my batteries then? Or destroying my IGBT if I chose to use those?

I also learned that my batteries have some sort of short circuit protection in them btw so I'm guessing it doesn't allow them to go past the 125a rating?

Can't really up the V much, maybe 53V from 4 batteries max. But that still means I need to lower my coil from 3.4mH to only .21mH according to this calc.

 

[(*steve*)]

Can't really up the V much, maybe 53V from 4 batteries max. But that still means I need to lower my coil from 3.4mH to only .21mH according to this calc.

And of course that will also reduce the magnetic field and the power which can be imparted to the projectile.

 

[CocaCola]

My job isn't to build anything but to suggest ways to improve things before a final design.

How do you plan to do that when you appear to not even know the first clue of how this all works? How in the world can you suggest improvement when you don't even know what is happening in the first place? The logic or lack of logic in your statement is mind boggling...

Believe me I've tired buying one from people who have a working one to save time.

Its a lot to learn in a few weeks, 3 weeks ago I didn't know what a IGBT was so...

If your goal was to have a working prototype to 'modify' you could have built one by now, or even build one tomorrow or this weekend... You can build a basic one tomorrow with a trip to the hardware store and Wal-Mart for under $20... Lots of easy to follow DIY plans...

Take for example these, sub $10 price tag?

http://www.jeffhove.com/robots/coilgun.html

http://www.angelfire.com/80s/sixmhz/cgkit.html

Easy to start modifying and cheap to do so...

Here my question, if my coil isn't going to allow the current to rise past x amps, do I still have to worry about destroying my batteries then? Or destroying my IGBT if I chose to use those?

Maybe if everything works as planned...

I also learned that my batteries have some sort of short circuit protection in them btw so I'm guessing it doesn't allow them to go past the 125a rating?

Maybe can't say I didn't design the protection circuit, but it very well will not allow you to use them in your application just as easily as it might not allow it to exceed 125A...

What did the manufacture say when you contacted them?

Can't really up the V much, maybe 53V from 4 batteries max. But that still means I need to lower my coil from 3.4mH to only .21mH according to this calc.

Yeah, pesky reality strikes again...

 

[(*steve*)]

My job isn't to build anything but to suggest ways to improve things before a final design.

I'd suggest the role of engineers is to improve on your design before a final design, but I'm just saying that from the point of view of someone who thinks that understanding the issues is important.

Engineers do the rest, people that went to school for it but don't have much creative/inventive of a mind.

Ooh, I bet they all love you.

I don't do electrical improvement

Clearly

but usually physical design improvements.

OK

That's what I'm trying to do here

No ot's not. What you're doing here is trying to make fundamental decisions about the power source and he coil geometry without any real understanding of the principles involved.

but unfortunately I first have to have a working coilgun before I can improve one.

Ask your unimaginative engineers to build one for you.

Believe me I've tired buying one from people who have a working one to save time.

And what do they say?

I'm sort of starting from the scratch in something I don't normal deal in at all

Clearly

so please excuse most of my ignorance but I am trying.

Honestly? Trying would be to at least consider advice given to you.

Its a lot to learn in a few weeks, 3 weeks ago I didn't know what a IGBT was so...

Yeah, maybe those unimaginative engineers of yours did spend their time at university for something after all...

 

[supak111]

Only more amps or more turns yields more magnetic field/power to projectile correct?

So to keep T constant say 1/2ms, I need to decide on (high amps & low mH), or (low amps & higher mH) correct?

If I am understanding this calc right, high amps lower mH seems to produce more power, then low amps high mH. Time still constant

 

[CocaCola]

My job isn't to build anything but to suggest ways to improve things before a final design. Engineers do the rest, people that went to school for it but don't have much creative/inventive of a mind.

...a little knowledge is apt to puff up, and make men giddy,
but a greater share of it will set them right, and
bring them to low and humble thoughts of themselves.

​

 

[supak111]

I never said they spend their time at Universities for no reason, where in the hell did you get that. I didn't even put them down in any way, they all make good money and deserve to do so. I don't even work with many electrical engineers, mostly mechanical. I was just clarifying my job that's all.

BTW guys I am not trying to improve the coils from other peoples designs, I'm simply trying to copy that part to my Volts and Amp specs. I want to use batteries for portability and high Hz if one day i want to hopefully shot faster but for now it simply to understand the limitations of the system. My improvement is in the construction of the whole thing.

And how can I build one when I'm here trying to figure out what kind of a coil I need to wind to have it work with my Volts and Amps and all I'm getting in return is lip about how I don't know the basics lol. I've already admitted I don't know much about it, why do you think I'm here asking questions man? If I know the geometry I would have already done it you are right. So now instead of quoting half my stuff and not giving ONE answer how about you try and give me an idea as to what my coil should look like if the end goal is high high hz and you already know my power supply

IN ORDER OF IMPORTANCE:

Figure out proper coil (see my q above) ---> barrel ---> figure out switching 80% done ---> start constructing my design

 

[CocaCola]

And how can I build one when I'm here trying to figure out what kind of a coil I need to wind to have it work with my Volts and Amps

How about you not get ahead of yourself? You don't pick and lock in parts until you have a working concept that you believe they will work with, you are doing everything all backwards and willy nilly...

I gave you direct links to two designs you can build for $10, there are many more designs on any given Google search page... Built one of those then make it a 2 coil design then make it a three coil, then get ambitious and make it a 10 coil... Learn some basics and working principles...

That or simply build your new revolutionary design you claim to have...

Its a 100% new design, no one out there has tried this. I may have made it sound dangerous, huge, TOO POWERFUL but believe me its really no. If I told everyone exactly how I'm planing on doing it everyone would understand but I simply can not share my design until I try it myself and see if its anything that could be worth something in the future.

and all I'm getting in return is lip about how I don't know the basics lol.

Quite the contrary, you have been given A LOT of solid information of what will and won't work but you glaze right over it as if it doesn't apply...

I've already admitted I don't know much about it

Yet, you claim to have a revolutionary design, even with your lack of the basic principles...

So now instead of quoting half my stuff and not giving ONE answer

You have been given MANY answers, you just don't like them...

how about you try and give me an idea as to what my coil should look like if the end goal is high high khz and you already know my power supply

How about you show us your revolutionary design and maybe we tell you want is wrong and why it won't work?

If you want me to design it for you (heck I'll even build you one based on said design) what is your realistic budget for those services? On that note don't expect me to entertain your unrealistic ideas...

 

[CocaCola]

IN ORDER OF IMPORTANCE:

Figure out proper coil (see my q above) ---> barrel ---> figure out switching 80% done ---> start constructing my design

Nope order of importance starts with grounding yourself in the science behind these devices so you can proceed to the above once you actually understand what is reality and what is unrealistic fantasy...

 

[supak111]

Problem is half the stuff that "unrealistic" is fixed by my design I just can't share it. It would make things a hell of a lot easier if I could.

Lets say that I want to make a single coil gun OK, but again that can potentially be fired @ 2khz. Please please just tell me what kinda of a coil, turns, gauge wires, would be best for my 40v 125amp power source?

I understand it will not have much energy as a single coil, can you just look past that so I can start somewhere, and then add more coils.

 

[CocaCola]

Problem is half the stuff that "unrealistic" is fixed by my design I just can't share it. It would make things a hell of a lot easier if I could.

Regardless of what you believe, trust me my money is on real world physics and the laws of nature, not your proposed (imaginary) ways to warp reality and break the laws of physics...

Lets say that I want to make a single coil gun OK, but again that can potentially be fired @ 2khz.

Lets say you Google 'Newton's Laws of Motion' OK?

Please please just tell me what kinda of a coil, turns, gauge wires, would be best for my 40v 125amp power source?

Best for what? There are lots of other variables that need to be factored in, all of them helping dictate what might be a 'suitable' coil design...

I understand it will not have much energy as a single coil, can you just look past that so I can start somewhere, and then add more coils.

Please review the links I provide (or one of the many others to be found) as they are proven working designs (now you have a working model and a working design to build upon) you can then modify to your new ideas one at a time and see what doesn't work...

 

[supak111]

My design wont be breaking laws of physics lol, I'm not one of those believers.

Can't use other peoples design because they all use stuff in their design that wouldn't work in mine, one SIMPLE difference is they all use cylindrical projectiles, I am using ball shaped projectile.

What other variables are required to figure out right coil design? Do you see if you guys can't even figure it out then how could I?

How about close estimate as to what gauge wire, and # turns will yield about 2khz pulse possibility at 40v 125a, projectile 3.5g steel ball bearing, velocity after one coil NOT important for now as I will add more coils.

 

[CocaCola]

My design wont be breaking laws of physics lol, I'm not one of those believers.

Could have fooled me...

Can't use other peoples design because they all use stuff in their design that wouldn't work in mine, one SIMPLE difference is they all use cylindrical projectiles, I am using ball shaped projectile.

Good thing that neither of the designs I linked used your proclaimed required cylindrical projectiles... One less part you need to modify, so you are ahead of the game...

What other variables are required to figure out right coil design? Do you see if you guys can't even figure it out then how could I?

Well 'we' live in the real world and accept that there are limits to what can be done, and some of use are grounded in or have an education in physics...

How about close estimate as to what gauge wire, and # turns will yield about 2khz pulse possibility at 40v 125a, projectile 3.5g steel ball bearing, velocity after one coil NOT important for now as I will add more coils.

Lets flatter you and assume your goals are realistic with that said, the velocity is damn important even for the first coil if you plan to rifle 2000 rounds a second out of that barrel... The projectile has to clear the load chamber in under 5/10000 of a second so the next round can not only chamber but be fired in that 5/10000 of a second time period... AKA it has to be at a very fast velocity nearly immediately...

And by the way you are still working backwards, you can't just randomly hard set components and then force things to work as you expect... The components need to be chosen for the the design...

Here is a good starting point... I know, I know NOT the answer you want but it's the best answer you are going to get, even if you don't like it...

Now return to reality and start with making a coil gun that actually fires a single projectile, using a single coil... Once you master and perfect that you can start to explore modifications one at a time towards your goals, until that pesky reality creeps up and forces you to reconsider your mods...

 

[CDRIVE]

Problem is half the stuff that "unrealistic" is fixed by my design I just can't share it. It would make things a hell of a lot easier if I could.

I've been waiting with great anticipation for when we'd get here. I'm not clairvoyant but somehow I knew it was coming! Go figure??

For what it's worth, it's a little known fact that the movie "Astronaut Farmer" was not
based on a true story.

FYI: There's a reason that spherical projectiles were abandoned a long time ago. There's also a reason that hard projectiles (steel ball bearings) are considered as verboten as pouring sulfuric acid down your barrel.

Chris

 

[supak111]

Slingshot ammo is steel ball bearings

PS spherical projectiles fly great if spun like a bullet out a riffled barrel, and military is using tungsten as projectiles for railguns cant get much harder then that.

 

[BobK]

Slingshot ammo does not travel at 2000 ft /sec. And there is a good reason for using a sphere in a sligshot. Without a barrel any non-spherical shape would tumble and travel in nothing like a straight line.

Bob