/diy/ - Do It Yourself

Pic related costs about two car batteries worth in the .gif's timeframe.

>>613056
looks interesting, is that an induction furnace of some sort?

>>613058
or is that temperature buildup a negative side effect of attempting to hold that lump of mass in place against gravity?

That could be a problem If I am to try and hold the mass in position

>>613060

Yeah, the temperature buildup happens as a side effect (Although obviously if you're deliberately melting things it doesn't count as a side effect)

To understand the heating effect, study "eddy current"

Here's something similar in the manufacturing process of a chain. Pretty neat.

http://youtu.be/8eBze0d0eHQ?t=3m48s

>>613085
Looks like you have to open that link the old-fationed way, you can't embed it or it won't start at the correct time. Or just move the time to 3min 48s.

>>613082
ah eddy currents heard of them, apparently used to locate iron ore deposits from specially equipped aircraft

>>613085
pretty interesting effect, it is likely that you would have to pump in quite a massive amount of energy to increase the intensity of the magnetic field to generate high enough eddy currents.

I guess my design parameters would involve what sort of material I am using, what sort of geometric properties the projectile has, and what is the maximum intensity of the magnetic field when accelerating/decelerating the projectile.

So if my understanding is right about the heat dissipation at a simple level, it all boils down to dealing with a resistor that would have some specific absolute maximum rating that depends on all the parameters involved.

In which case Power = ( RI )^2, R is related to the material properties and I is the eddy current generated which is related to the magnetic field intensity.

I'd have to burrow into it to see if it all adds up and know what parameters to tweak such that the heat build up is within tolerance.

>>613094
you will want to learn about induction. perhaps start off with basic electromagnets. you could put one coil of wire on each end of a horizontal track with a ball bearing on it. energize the coils to attract or repel by reversing the polarity of the current.

then you can push and pull the bearing along the track. once you have that figured out you need to work out using multiple coils and timing their firing sequence so that they repulse and attract at the right time to propel the object.

>>613111
sounds like a good simple start

A solenoid probably works in a similar fashion

>>613113
they have some more mechanical parts but yes, exactly how a solenoid or a relay works.

>>613094
If you are making a "normal" coilgun (coilgun, mass driver, same principles) design, then the projectile would be ferromagnetic and it's attraction to the magnetic field in the coils would be what propels it. The eddy currents would be an unwanted side effect that introduces energy loss.
If you're making an inductive one, then your propulsion would come from interaction between the magnetic field of the powered outer coils and the induced magnetic field in the projectile's coils. In this case eddy currents is what powers the projectile's coils. Needless to say, this version is far more complicated.

what iu r looking 4 is "gauss rifle" you sick anon basterd! https://www.youtube.com/watch?v=KikIp_yAXvQ (hope you'll find it fruitfull)

>>613443
looks pretty neat,

I'd like to experiment with making a rocket launcher of some sort with one of them.

Either have it in two separate stages where you launch the rocket first then ignite the thruster or a hybrid where you fire up the thruster and accelerate with the coil gun as well which sounds similar to launch assistance using a steam catapult for aircraft.

The latter would be harder since you have to take into account that firing the thruster can damage components.

Having an RC rocket or glider launched from one of them sounds like fun, but you'd have to take into account the electromagnetic field fucking up with your electronics which would be a pain to shield against.

Though playing around with a water propelled RC glider sounds way easier to implement. I've already made a water bottle rocket launcher ages ago back during high school, shit was cash.

>>613017
when you say you're playing 4X i assume you mean you're extremely drunk.

I'm not saying I want to make it, but do you guys think a high powered coilgun could be made and be usable by a normal person? Something that could puncture skin and cause damage. I definitely don't want to use anything like this on a person or animal, I'm just wondering if it's possible.

>>613060
Not quite. In that case they're doing it completely on purpose through induction heating.

>>613966
Yeah. There are a few good examples on YouTube. Rail guns are much better though. Coils are inherently inefficient. You wastea lot of energy creating the magnetic field.

>>614022
They might be better in theory, but he wants to build one in real life and probably with very limited resources and knowledge.

>>614022
And how exactly a railgun is more efficient?

>>613943
OP may mean that, but he may not. 4X is a subgenre of strategy games; it stands for "explore, expand, exploit, exterminate." Games like Civilization and AoE fall into this category.

>>614050
You're right. In theory coil guns can be 90% efficient, but most hobby made guns are less than 10% efficient.

Professionally made rail guns are about 50% efficient. Hobby versions probably have a slightly better efficiency than their coil gun counterparts.

For a coil gun, you have to shut off the coil and collapse the magnetic field before the projectile passes the mid point of the coil. Its very difficult to get the timing just right.

For a rail gun, your biggest losses are in the contacts between the rails and the projectiles.

>>614174
>For a coil gun, you have to shut off the coil and collapse the magnetic field before the projectile passes the mid point of the coil. Its very difficult to get the timing just right.
Can't you make a mechanical breaker at the points so you don't have to rely on software speed to do this?
Basically the projectile gets sensed just before reaching the middle point with the help of a superfast sensor(suggestions?) and kills the power to the coil.
I'm also wondering how to simulate and optimize the coil windings, voltage, current and other theory without actually testing.

>>614343
Most certainly not a mechanical breaker. Relays are too slow and most would just weld together from the current.

What I'm doing is using IR sensors to sense position, uC for the logic and switching with power MOSFETs (via drivers ofc).
Software is the fastest part of the whole thing.

Basic optimization is to have the coils slightly longer than the load, more turns is better, lower resistance is better. The higher the voltage the more power, as long as the system can handle it and the current that results from it.
Magnetic saturation is a problem though since it limits the maximum power of an iron projectile based coilgun even in hobby designs.

>>614354
Sorry, I meant analog.
Some kind of relay switch that kills the power to the coil when it passes midpoint
I was wondering about the windings vs thickness.
What formula is used to calculate force? I got this thin wire that can make shitloads of turns but I don't have access too thick copper wire and first hand copper is expensive as hell.

>>614362
The force formula bloody complicated since the exact force depends on source voltage, coil geometry, coil resistance, winding count, time, materials surrounding the coil, projectile position, projectile composition, projectile geometry...
zzz haven't bothered with that.
But to simplify it, the force is directly proportional to number of turns multiplied by the current passing through (ampere-turns). Keep in mind that thin wire will have both higher ohmic resistance and a higher inductance.

>>614365
>Keep in mind that thin wire will have both higher ohmic resistance and a higher inductance.
I'm aware. But you can make more turns with that.
That's why I asked for a formula. To check if the loss in resistance could be made up for in turns.
Also how much amps we talking about here? I tried hooking up the same wire and got nothing. My power supply can only do 3 amps but I have a battery that can do 90 amps sustained @ 12 volts. I'm a little careful with that since you know, 90 amps on a bare wire without suitable resistors.

>>614442
www.coilgun.eclipse.co.uk/coilgun_fundamentals_1.html

This article explains why there is no simple formula to use. It also answers most of your questions.

>>614442
Why aren't you using inductance laws and other Electromagnetic equations? Literally they teach that at low-level physics, though it does take integration to get good results, and Calc III/vector and area rules if you're going for even more accuracy. Since all you're doing is making solenoids/coils all that stuff has been solved for like 120 years.

>>614515
>Why aren't you using inductance laws and other Electromagnetic equations?
Not him, but that shit explodes on your face immediately when you try to apply it to something practical. In other words, in any situation where you can't use silly assumptions like "infinitely long", "infinitely thin", "constant permeability" and so on and so forth.

So when did this board turned to "I don't know how to do anything, give me your creativity /diy/" posts?

>>614535
It's called advice from people with experience you cockmuncher
I don't bicker at all the threads about wood or other simple stuff like that either, yet they are so simple to do.
It was always like this.

Anyone can create a coil and fire off their fancy weapon without any knowledge. The trick is to make it good. And since the theory is fucked up without a simulator it takes experience.

>>614530
>when you apply it to something practical
Take more engineering and physics courses.

>>614538
Then it isn't first year classes anymore.
I rather ask computer's opinion. Or check some book.