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LAN_403

alf

Fri May 11 2012, 11:17AM

Registered Member #3925 Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121

hi,

i'm thinking about making a railgun, lol
but idk where to start cos there is not much about railguns on the net, haha
see the attached crappy drawing of my design, do you think this would work?
i was planning to use copper sheet as the rails, and cast an aluminium projectile or something
using 22000uf at 400v capacitor bank.
and maybe inject the projectile with compressed air.
any suggestions? cuz i really dont know what i'm doing.

thanks, Alf.

Saz43

Sat May 12 2012, 06:43AM

Registered Member #1525 Joined: Mon Jun 09 2008, 12:16AM
Location: America
Posts: 294

If you have no idea what you're doing, it's probably wise to start with photo-flash capacitors, that way you can make your mistakes with a lower chance of dieing.

alf

Sat May 12 2012, 10:17AM

Registered Member #3925 Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121

Saz43 wrote ...

If you have no idea what you're doing, it's probably wise to start with photo-flash capacitors, that way you can make your mistakes with a lower chance of dieing.

thx for your reply,

correction: i do know what i'm doing, i just dont have any experience with railguns, plenty of experience with high voltage caps, haha.

thx again, Alf.

Pinkamena

Tue May 15 2012, 10:37PM

Registered Member #4237 Joined: Tue Nov 29 2011, 02:49PM
Location:
Posts: 117

Well, as long as you know the working principles of railguns, everything should come pretty naturally. Try reading about other peoples railgun projects, learn from their mistakes, and be inspired by their design.

Barry

Wed Jun 13 2012, 08:39PM

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

It seems to me like railguns are an exercise in precision mechanical fabrication, while coilguns will work with any random iron that fits loosely in the barrel. My shop skills suck, so I chose coilguns, lol.

Cheers, Barry

Gomez

Wed May 08 2013, 10:53PM

Registered Member #2328 Joined: Tue Sept 01 2009, 03:44AM
Location: Denver, Colorado, USA, Sol-3
Posts: 7

>hi,

>i'm thinking about making a railgun, lol

And yet you tell the other guy to take you seriously? When you can write
as if you're an adult, maybe you'll get more constructive advice.

>but idk where to start cos there is not much about railguns on the net, haha

That statement right there proves you haven't looked, or you haven't the
first idea where to look. Google Scholar. Your local library.

>see the attached crappy drawing of my design, do you think this would work?

No. But I don't have to look at it.

> i was planning to use copper sheet as the rails, and cast an aluminium projectile or something

Blah blah. What are your boundary conditions?

>using 22000uf at 400v capacitor bank.

Oh, do you have that already?

How much stored energy is that? Quote the formula.
You should know it by heart, it's quite simple.

>and maybe inject the projectile with compressed air.

Maybe?

>any suggestions? cuz i really dont know what i'm doing.

Nooo kidding. Now here's the problem, Alf: the other day, a young man
right here in the land of the free and the home of the brave got arrested
for a dumb rap song he uploaded.

Yeah, it was in the news.

In this litigious, lawyer- and trigger-happy society most of us (in the USA
at least) find ourselves in, can you imagine what would happen to one of
us - that is, some of us with families, with MORTGAGES, you know - whole
lives to lose, not just the contents of our bedrooms if the cops come
knocking... do you see there is really serious liability now?

No one in their right mind is going to take you seriously when you write
as if you are young and ignorant. Ignorant is fixable, but only if you live
long enough to stick your nose in some books for a while.

Start with math. And learn the basic physics. Figure out what
"inductance gradient" is and why it matters. Figure out what your
budget is. You do realize you have just announced your intention to
get into one of the most expensive amateur HV hobbies there is, short
of say, fusors? You CANNOT do a railgun cheaply. Not even dangerously,
let alone safely. Priced copper lately? You'll be needing many pounds of
high grade stuff. All the other materials likewise very expensive - even
bolts.

The fact that you're starting with some fantasy drawing before you even
have defined your project shows that you need to learn a few things
before embarking on such an ambitious project.

In the real world, you start with an actual goal you want to achieve,
and you have to be serious about it. What mass, how fast? Now at
1% (if you're lucky) conversion efficiency, how much energy do you
need?

How are you planning to stop your projectile if you succeed? Describe
the safety systems. Describe your instrumentation. How will you
study the armatures if you do not recover them intact? How will you
do _that_?

How much money do you have available? What kind of fabrication
resources - and experience - do you have? You will need things like access
to, and experience with, real machine tools such as metal lathes, milling
machines, and so forth.

OBTW, machining copper is a pain in the ____ -- even experienced
machinists dislike dealing with it, and you'll want special cutters,
and blahblahblah, there's a thousand things you need to be good at
that you've already made plain you are not even close to having
experience with yet.

You need some schoolin' son. You will need solid engineering knowledge
to contain tremendously dangerous forces safely, both in the high
pressure gas gun injector if you decide to experiment with that
(as people like Sam Barros have discovered, they are not without
their own challenges) but also the magnetic forces in the gun.

What will your ultra-low-inductance current path between gun,
switches, power supply, etc look like?

If your goal is, "hurr, build some kinda railgun" then go do some more
growing up, and come back when you can convince someone that they
should let you HAVE several tens or even hundreds of kilojoules of fast
energy storage in your garage. It represents a danger to you, the house
or school it sits in, and the property and persons nearby.

Legalities aside, it's not unlike playing with explosives. High energy
pulsed power of the sort we're talking about won't just electrocute you,
it will blow body parts off of you. You can't sew a vaporized finger back
on, no matter what you have seen on TV.

I for one would not care to be one of your neighbors. You need
competent adult guidance IMO. I'd also have your parents and or
teachers read thru their liability and property insurance to see whether
railguns are covered.

You can make pretty pictures after you've got the vaguest idea of
what the rest of your system will look like. The gun is the sexy part.
But it's how well you do the rest of your system that will spell success
or failure.

How do you plan to take measurements? If you don't, then how
will you know what results you really got?

Forty

Sat May 18 2013, 05:48AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

Do you know why my physics students love me so much? Because I'm not a condescending asshole like Gomez. So you think you're smart? Of course, we all do, we're all science people on here, we're all smart. But you can correct people, and give them advice, in a whole multitude of ways that are much more helpful, and less demeaning than that. Despite how someone might want to type out a post, with all the "lol"s or laughing, that they might want to add to their writing to add a bit of their personality, there's no retarded people sitting around with capacitor banks and asking questions about what to do with it, so please don't treat them as one. When I meet people in the real world, and they even know what a capacitor is, I'm impressed, so don't belittle people for asking questions.

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