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1.5kJ Induction Launcher

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Daniel Uhrenholt

Fri Nov 17 2006, 06:19PM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

Hi all.

This project started out about 4 months ago, and now it is finaly working.

But I still need to get this thing outside to see what it can do, there is not sufficient room in my
apartment

It`s made out of 4 Siemens 350V 6000uF lytics in series-parallel to get 700V 6000uF, and a huge SCR and one fat diode.

The diode is a SD3000C10K and the SCR is a T9G0161203DH, both are huge PUCK style rectifiers

But i still need to make a stepup transformer so i can get this thing up to 700V

(A modified MOT with extra shunts and a new secondary)

I will post a movie when i get it outside.

Some pics:

Setup on my bench in my bedroom

Let`s just say I made "some" marks in my ceiling

And thanks to Finn Hammer for helping me get the parts.

Cheers, Daniel

Mod edit: merged double post

The weather is bad here in Denmark, so i can`t get it outside yet...

But i have a question:

How can i calculate or measure the velocity of my projectile?

I don`t have a chronograph, and would like to calculate velocity and efficiencies with different Al. rings.

Daniel

Marko

Sat Nov 18 2006, 01:52PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Why don't you just use a voltage doubler to charge to 700V?

You would need some kind of choke for current limiting but it's still lighter and less messy than mot..?

I like your housing of coil.. is that teflon box?

Daniel Uhrenholt

Sat Nov 18 2006, 05:04PM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

Hi Firkragg.

I don`t want to use a voltage doubler, because i think it is cooler and smarter to have a transformer with internal ballast. No need for a big charge resistor...(And just to say that i made it myself

)

But what the heck, i may try a voltage doubler just so i can fire it up to morrow!

But a choke or ballast would fill almost the same as a MOT or more, I only have some BIG ones to my classic Tesla coil experiments..

The coil form is made out of my favourite material POM, easy to machine and it can take some bumps.

And a little picture of the coil:

Cheers, Daniel

Marko

Sat Nov 18 2006, 05:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I tought a doubler would be 'cooler and smarter', but do as you want.

Capacitive (small motor start cap), inductive (fluorescent or mercury lamp ballast, small transformers, etc.) or resistive (lightbulb?) ballasts would work well.

Nice coil indeed; be sure to have enough pressure n it to keep it in piece...

Daniel Uhrenholt

Sat Nov 18 2006, 06:12PM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

Oki, I will try the doubler tonight if it possible with the parts i have.

I have 2 5600uF 400V DC electrolytcis, but i dont have many diodes... I have some from microwave ovens, but have no idea if they will work?

This will be my first voltage doubler...So it`s very new for me.

Do this look right?

But I will make my own transformer, because i only need to get the wire for it.

EDIT

I don`t think they will, they are rated 12000V 500mA

...

Sat Nov 18 2006, 06:33PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

5600uf is way too big, I try something like 500-1000ufd.
As to the diodes, a standard 1n4007 would work fine...

But looks good otherwise!

Daniel Uhrenholt

Sat Nov 18 2006, 06:47PM

Registered Member #125 Joined: Fri Feb 10 2006, 01:52PM
Location: Aalborg, Denmark
Posts: 155

What board? I don`t under stand

Oki about the voltage doubler, i have some 470uF 400V from a broken TIG welder i can use.

I`m scrap hunting twice a week

Daniel

Coyote Wilde

Sat Nov 18 2006, 07:07PM

Registered Member #175 Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111

It all looks very sleek; good job.
As for measuring the velocity, once you get it outside you should be able to estimate the hight the projectile gets to; ignoring air resistance, you should be albe to get at least a first-order approximation with simple kinematics... and for a simple disk, the drag equations aren't too hairy either.

...

Sat Nov 18 2006, 07:53PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Sorry, the refence to drilling to board was not realted to you (too many things going on at once)

As to calculatong the velocity of the disk, you will probably have to go for a photogate based cohornograph.

Have a led and a photodiode 1cm off the coil, and one 11cm away from the coil. You might have a hard time getting it to trigger well, but...

Reaching

Sat Nov 18 2006, 08:20PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

i have a velocity measurement circuit which is very accuratly and developed a new fotogate with IR diodes which can switch over a distance of about 10cm or more. the simulation of the fotogate shows that it can trigger up to a time of about 150Âµs , maybe you can use it for your ringlauncher to measure the exact velocity

dont know how fast a ringlauncher projectile can be but up to a velocity of about 200m/s it should be no problem for the new fotogate

its in this thread but nobody seems to care , dont know if everybody here like complicated calculations

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