Yamato Project

keantoken

Member
2006-08-10 12:32 am
Texas
Hello people.

So I was walking around in the gym one day, and my friend Brandon sighted me and immediately took me aside to inform me that he had recruited me into his own Japanese navy fleet. I am now assigned to task of constructing a battleship of unrivaled proportions: It is to be five feet in length. It is to be equipped with four BB-shell turrets, each with three barrels. Furthermore, it also requires a remote-control system, with which to aim and fire the turrets, engage an on-board water pump, turn the rudder and control the throttle for both forward and reverse drive.

This project is for the Model Warship Combat competition, whenever and wherever me and my friends may be able to join, hoping that there will be enough cooperation to get the job finished.

At any rate, I was planning on running the entire ship with two 6V lantern batteries, and I believe that will be enough.

I have decided that my first project will be prototyping for the coilguns. My main requirement is that I be able to generate enough voltage in a short enough amount of time for rapid rate of fire.

Thus, camera flash circuits from disposable cameras do not meet my requirements. This is where I must design my own circuit.

I am currently planning on using the PUT complimentary pair documented here to oscillate and drive a step-up transformer to achieve the required voltages.

The oscillator described on that website has very fast switch-on time, thus there will be plenty of high harmonics which I may desire to filer out in some form or fashion so as not to interfere with radio control circuitry, although I have second to no experience with this sort of thing so it may not be required.

The attached diagram is the circuit I plan to use to charge up the main capacitors which will then discharge through the coil.

The output is taken from between R2 and R3 by a MOSFET. However, I have no experience with MOSFETs whatsoever so I have no idea if I've even hooked it up right! The inductor value is an educated guess, as the inductor I have on-hand is homemade with four turns for the primary on a toroidal core I ripped out of a PC power supply. The secondary is not any standard value right now as I am planning on rewrapping it for greater number of turns. The primary currently has 4 turns and the secondary currently has 79 turns.

The circuit oscillates at about 5KHz, though I want to get it to at least 15KHz so that it's as far out of the human hearing range as possible.

The capacitor being charged is C2.

So, do you think this will work?

[IMGDEAD]http://img149.imageshack.us/img149/6344/coilgunprojectoq2.th.png[/IMGDEAD]

Humbly Bumbly,

- keantoken
 

keantoken

Member
2006-08-10 12:32 am
Texas
There are plenty of coilguns using simple camera flash units. I'm experimenting with using one right now.

I have the flash capacitor (120uF) paralleled with a 470uF 200V capacitor. So far I'm not getting any results, except for loud sparks and whenever I get a strong magnet near I can feel it jump in my hand.

I imagine if I have enough windings on my coil, the problem is that the BB isn't close enough to it. I'm using a steel BB about as wide as a pencil.

I might post pictures soon.

- keantoken
 
I would think it would be pretty easy to adapt a paint ball gun for this sort of duty. I don't know how much time you have for development and assembly, test and debug, but the fastest way to do anything like this is to use off-the-shelf hardware. Common RC servos can be used to trigger the gun, rotate the turret, and set barrel azimuth.

I_F
 

keantoken

Member
2006-08-10 12:32 am
Texas
I plan on using servos for aim, that's not a problem. I'm willing to use coilguns because I have no resources beside what I can buy from radioshack and even then I scarcely get anything over $10 on a solar eclipse.

I have practically all year to do this, too. So I can pretty much take as long as I want as long as my friends don't get bored.

- keantoken
 

keantoken

Member
2006-08-10 12:32 am
Texas
Alright, I'm kind of into tesla coils right now, as I found it would be of help to gain the experience with high voltage stuff.

I just had an interesting experience, and this is why I'm posting...

I was using the below circuit, using an old flyback transformer as the output coil, and I substituted R1 with a 1 megaohm POT so that I could vary the frequency.

I turned the unit on, with no sparks. This was somewhat dissappointing. Then I decided to start tweaking the POT to see if I could find a resonant frequency...

Suddenly, the inside of the POT was glowing this eerie orange color and white smoke was billowing out!

I believe this signifies a great moment in the production of this project... And it is a bit like deja vu as before this I had neglected to use a high-current diode at the MOSFET's source, resulting in neat (and smelly) ribbons of smoke.

Thus, I find it very fitting, to name my first tesla coil, the 'Smoke Machine'. It's even more fitting when you consider the only sparks I've gotten out of it are from the battery terminals when I connect it to power!

It's getting ever so closer to completion and working order, however. Perhaps I never built a decent amplifier in any sense... But I don't know of any way this could not work.

SmokeMachine2.png


- keantoken
 

keantoken

Member
2006-08-10 12:32 am
Texas
Thanks, I never thought of using an inverter like that! Unfortunately, I'm still limited to four lantern batteries, so I'm going to make the most out of them. I'll remember this, though.

Hmmm... Since I exploded my old POT, I think I should consider adding safety measures for such...

My new circuit is as follows. Q3-Q5 are a current mirror, so that Q3 and Q5 absorb more of the shock than the Potentiometer. Normally I would just upgrade to a higher-power POT, but I don't have that resource available. Who knows, perhaps I'll get a transistor to glow rather than a potentiometer... I used to have a resistor connecting Q5's collector to ground so that it would have a bias current, but according to the simulation the momentary short via the MOSFET's miller capacitance is enough to turn it on. If it doesn't work in real life, I'll add the resistor again. The reason for going through all the trouble to protect the POT is because I don't have the resources where I could find a higher power one, I only have the Radioshack by my local walmart. C1 is to speed up oscillation frequency, and yes I now how it works.

SmokeMachine3.png


- keantoken
 
I don't know if you are aware of Barry's Coilgun Design Site or not but I've been reading his material for years. Good Info @ http://www.coilgun.info/home.htm

You may want to consider the use of compressed air (or gas) as a back-up plan - for a number of reasons that I won't take the time to go into here. Are you familiar with the math involved with the fire control of gun systems? I spent six years in USN as a missile FC tech and things are just a tad more complex than "fire on the up-roll" - well - that is assuming that you actually want to hit something......;)

Take a look at http://www.hnsa.org/doc/firecontrol/partd.htm
 

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keantoken

Member
2006-08-10 12:32 am
Texas
Thanks, Thomas. I don't think I'll need to use on-board compensation mechanisms because during the competition no one bothers shooting until they're at least 5 feet apart. My friend will probably be interested, though, if he hasn't already found the page.

We are planning on using compressed air as a backup plan, if we find that coilgun stuff just isn't practical. At any rate, I will at least have a working tesla coil by the time this is over, and if it all doesn't work out, me and my friend plan on having our own private demolition project that will take place after we have successfully mounted several high-voltage weapons on our ship... Nothing less than ion guns and mass accelerators and plenty of homemade torpedos. Missiles also if we can manage it...

We have plenty of dreamy ambitions, at least!

Darn, this thing just won't work without smoking all my potentiometers... :(

- keantoken
 
keantoken said:
Thanks, Thomas. I don't think I'll need to use on-board compensation mechanisms because during the competition no one bothers shooting until they're at least 5 feet apart. My friend will probably be interested, though, if he hasn't already found the page.
- keantoken

Which means that if you can start firing when you are 20 ft. away you will most likely prevail - and that is the goal isn't it?
:D :D :D :D :D :D

Ya gotta figure that if you aren't trying for increased range and effective fire power that the other guys ARE! :hot: Ya better be ready or you'll be fish food. :bawling:
 

keantoken

Member
2006-08-10 12:32 am
Texas
The main reason I'm trying a coilgun is because I can easily experiment with the parts I have on hand. Compressed air is somewhat expensive, and money is exactly what I don't have. For the moment at least. And we're not optimistic.

Also, an airsoft gun won't work, we need something that fires real .177" BBs. The idea behind this battle is real demolition, folks. ;)

That means that we're going to be punching through the other ship's hull and actually try to sink it. So from what I know, the way the ships are built, it takes a couple tries to punch a hole with compressed air. Thus, if I can get better firepower with a coilgun, then we rule.

Which means that if you can start firing when you are 20 ft. away you will most likely prevail - and that is the goal isn't it?

I have to admit, that would be pretty cool! But the rules don't allow automatic tracking/firing system, so...

At any rate, to fire a small projectile like a .177" BB, I figure I'll need either a small coil and higher voltage, or a larger coil and farther distance between the coil and BB. Am I right?

- keantoken
 
pinkmouse said:
Putting aside the inherent risk of this project, and letting my inner child speak, you'll be going at each other for weeks to do any real damage with those tiny BBs to a boat that size. Just stick a ram on the front underneath the waterline. ;)
hmmmm......Underwater spear gun perhaps? :devilr: OR underwater coil gun that fires spears...hmmmmm :bigeyes: Better yet - make the spear hollow to allow for water to flow into the hull of the impaled "victim"....:D :D :D :D :D :D
 

keantoken

Member
2006-08-10 12:32 am
Texas
Ah, yes, I did think of that, but unfortunately the rules don't allow for ramming...

About the inner child, Pinkmouse, I have something I say:

"You must learn to embrace your inner madness before you can ever hope to change it"

Unfortunately, when I finally embraced mine, I liked it too much to let it go... Insanity is just... So... Liberating...

Yes I did look at the coilgun site, I played with the coil simulator and the RLC simulator, I'll probably be looking at it later on more.

Does anyone know how to make an easy hi-wattage resistor in the 330milliohm range? I can't get great resistors at radioshack, so I need some true DIY advice. I thought about pencil graphite, but I'm not sure as I remember the stuff burning bright orange while I was messing with my store bought tesla coil.

I've heard of such things as water resistors, but water eventually dissipates into hydrogen and oxygen, so...

- keantoken
 
Must the battleship resemble the WWII type such as the USS Iowa or USS Missouri? Or could they resemble one from another time? Could they be a future design or self design that differed from conventional models - say one with sloping or slanted sides and superstructure? What are you allowed for construction materials? Balsa wood? Kevlar? :bigeyes:

Water resistors? You are floating on some of that stuff!!
 

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keantoken

Member
2006-08-10 12:32 am
Texas
It's not the construction materials that are limited, but your ship must be able to sink. From what I have read on the rules, if someone suspects you of putting too much armor on your ship, then they will test your armor by dropping an iron slug of some type down a long tube. If the slug does not penetrate, then you're legal. If not...

It's generally a good thing to not be suspected of such, because penetration testing can flatten your chances of winning the tournament...

Water resistors? You are floating on some of that stuff!!

Hehe, yeah. As far as mounting ion guns on our ship goes, me and my friend have been joking around about hiding the gun in a hidden panel. He says that when all hope seems to be lost, suddenly the top of the ship will break apart and this strange-looking device will emerge, sending jolts of electricity to the other ships and making them explode.

Sitting on water means decreased resistance through ground, so I'm thinking for increased reception I could coat the bottom of the ship with a layer of aluminum foil, and connect that to the ground on my receiving circuit. Not to mention if I did manage to fit an ion gun in there somehow, the decreased ground resistance would multiply the effects of the ion gun... That is, if the beam just didn't bend over and go right into the water. I'm not sure how well it works, but from what I know, using a pointed objects will direct the flow of electrons, and this is the principle of the ion gun.

Lordy, how would I get a high-power 1 Megaohm POT?

- keantoken