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Ed Caffrey's Workshop Talk to Ed Caffrey ... The Montana Bladesmith! Tips, tricks and more from an ABS Mastersmith.

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  #1  
Old 10-14-2006, 06:31 PM
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B.Finnigan B.Finnigan is offline
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Induction furnace build begins

This is a duplicate post from another thread on Ed's forum regarding induction furnaces.


Induction heating:

It's very similar to a microwave oven just with alot more juice and water cooling the copper coil. The electromagnetic waves vibrate the steel molecules and make heat. It's much more like the induction kitchen stoves that the ferrous pan reacts to the magnetic field and the pan it's self makes the heat.

Description of induction:
http://en.wikipedia.org/wiki/Induction_heating

Cool stuff to read about.

http://www.dansworkshop.com/Induction%20Heating.shtml

http://www.powerlabs.org/indheating.htm

This company makes remote heads that can be fed from a main power/Rf supply. You could have a head next to your anvil and one over across the shop for HT/quenching. A third one cold be ran for brazing/soldering.

http://www.ameritherm.com/heatstations.html
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Old 10-14-2006, 06:33 PM
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After rumaging around in my electronics stash I discovered I have almost all the componets I need to make a small induction furnace. By next week the HV capacitors will be here and it might be working. I used to do alot of tesla coil and Jacob's ladder type projects.

The most fun was the rail gun, it could launch an aluminum cylinder several hundred feet just with HV electromagnetism. It was not very accurate since you can't put a rifling spin on it for stabilizing. The military is right now testing a very large version of one that fires a tungsten/aluminum sabot at velocities that are many times faster then what chemical propellants can produce. The program "Future Weapons" on the Discovery Channel did a segment about it. As soon as they fiqure out how to make the power generator and capacitor banks smaller it will be tank/mobile mounted.

http://science.howstuffworks.com/rail-gun.htm

A simple homemade railgun with videos:
http://scitoys.com/scitoys/scitoys/e...n/railgun.html

Last edited by B.Finnigan; 10-14-2006 at 08:30 PM.
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Old 10-14-2006, 07:07 PM
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This morning I ordered the HV capacitors and completed the spark gap chamber and the coil. This will be a prototype learning project. Once I play with it and understand more about how it works I will start a larger one. The commercial ones use solid state voltage multiplying and high speed semiconductor switching to produces higher fequencies. For this style of unit the parts are easy to get and not too expensive. A rough estimate for the cost is around $150. I bought the 15kv transformer eight years ago new for $75. The capacitors are about $40 and I am probably using more then needed for it to work.

Ebay will have everything you need including the tungsten spark points. I allready had those for my arc smelter. The rest is just scraps of stuff that is probably allready in your shop.

The spark gap chamber was made from a plastic electronics enclosure. I made a 1/4" plexiglass lid so I can see the spark. The lid also has two threaded holes on opposing corners. This is so I can flood the chamber with CO2. The sparks will split O2 molecules into single oxygen atoms thus creating an oxidizing enviroment. This would quickly destroy the plastic and plexiglass.

On each side of the plastic box I have a 1/4" aluminum plate in which I tapped a 3/8" threaded hole for the adjustable tungsten contacts. The plates are secured with two 10-24 bolts, one on each side has the threads on the outside for terminal contacts. The bolts were bored out to 9/64" and swaged in two tungsten rods that were ground to a point. After the furnace is completed I will need to tune the circiut with the spark gap by moving the tungsten contacts closer together or farther apart. Tungsten can withstand high heat and is very corrosion resistant. It will also not erode off as fast as most other metals would from the continuous sparking. I will most likely build a larger box since this one may end up melting. That way I will have a back up ready to go.

After the box is flooded with CO2 I have two nylon toilet seat bolts that I shortened that will plug the holes on each end. I anticipate having to refill the chamber each time I use it but CO2 is cheap.



The coil is 3/16" copper grounding wire from the hardware store. I wrapped the coils around a 3/4" chunk of dowel. The ends were forged flat for securing it to the base. They are secured onto a piece of asbestos since it is an electrical insulator and can take high heat (yes I wore a respirator while cutting and grinding it).

The asbestos was then secured to a chunk of 1"x1/8" angle iron. The angle iron is then bolted onto a chunk of furnace brick.



This coil may be too much of a load for the circuit but I will not know for sure until I light it up. Way down the road when I make a bigger one I will have to use copper tubing and pump water through it to keep it cool. Even though copper is non-ferrous with enough power the coil will also heat it's self.

The "plans" I am using are posted here:
http://www.powerlabs.org/indheating.htm

I will be using a 15Kv 60Ma transformer with 4 Parallel 30Kv 500pf capacitor bank. The transformer itself can jump a spark 3+". The tranformer on the above website must be a newer solid state unit, that spark gap is very short. The new ones have to have a short circuit protection built in per new government laws. That does not let them work real well for sparking type projects. A 30 Ma solidstate coil will cut out at just over a 17Ma surge. If anyone else is planning on making one of these don't buy a solid state unit, go to Ebay and find a used coil. Remember they are very heavy and the shiping may be 2-3 times that unit cost.

I am always so glad to see my government knows how to protect me. We should be able to damage ourselves in any way we see fit in the pursuit of fun.

Last edited by B.Finnigan; 10-30-2006 at 11:55 AM.
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Old 10-14-2006, 09:06 PM
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If this setup works and I can fiqure out how to make it bigger then forging and HT'ing knives will get a bit easier and possibly cheaper.

The advantages of inductive heating over propane:

1. No excess heat to heat your shop (and you).
2. No heavy propane tanks to re-fill.
3. No refractory and refractory coatings to mess with.
4. Pinpoint heating of certain areas.
5. Consistant heating temps.
6. Placed closer to your anvil, press, power hammer and quench tank. (1095???)
7. No CO emmisions
8. Quieter.
9. Your eyebrows, beard and moustache will actually be able to grow back!
10. Less decarb and oxidation

I have a theory that you may be able to draw temper a knife by running the spine along the outside of the coil. What do you guys think????
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  #5  
Old 10-14-2006, 09:21 PM
Greg obach Greg obach is offline
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I think its fantastic.... if you can get this to work... wow

the cheapest i've seen for sale was....somewhere round 2000 bucks.. used...

its a great experiment.... i'm rootin for ya...

Greg


the small demo vid i saw.... was for making bolts... and that coil heated up those bolts in a jiffy
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Old 10-14-2006, 11:17 PM
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Kayne and Sons has one for $3600. It's thier "basic" unit, it only get spendier from there.

http://www.blacksmithsdepot.com/Temp...orge_Basic_Kit

Induction video (Dang that's fast!!!):
http://www.inductionatmospheres.com/...theating_2.wmv

The video is from Induction Atmospheres.

Last edited by B.Finnigan; 10-15-2006 at 12:18 PM.
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Old 10-14-2006, 11:36 PM
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Hey Brent,

I can't wait to see how this turns out. Keep us posted!


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Old 10-15-2006, 10:59 AM
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Brent,

This is great. Why did you choose the spark gap over the solid state design (the dansworkshop one)? Was it just the cost differential? I read through both designs and had printed a lot of the info from the dansworkshop one, since that one appealled to me a little more.

Can't wait to see you get this going. Have you read any on stray magnetic field outside of the coil? That was another worry I had. Anyway, this is cool.

--Carl


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Old 10-15-2006, 12:12 PM
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I wanted the first one to be as simple as possible and not cost alot. Dan's workshop page does not have any componet values listed on his schematics and the componets can get very pricey for the voltages and amps used. I would be buying several of the same componets to possibly find the best one. Some of them would have to be ordered to.

I have been reading up on cascading diodes for voltage multiplying and I have done a couple projects where I doubled and quadrupled the voltages. To me that seems like the next biggest improvement, to get rid of the heavy innefficient coils and go solid state. For right now the spark gap switching will keep the frequency lower giving a deeper penetration but taking a bit longer.

This coil/spark gap design will let me and others get one built real fast and start playing. Just the SCR itself will cost more then the entire project ($180) will. But I plan on building quite a few down the road as time and money permits. All along I will be focusing on forging and HT'ing.

I have looked at alot of commercial units and none of them had any type of shielding so I assume that the field is concentrated inside the coil. I know the spark gap unit will play hell on AM radios that are nearby or maybe not so nearby.

One of my Tesla coils would wipe out my mother in law's antenna TV and she lived 400 feet away at the time. It also blacked out our TV with a video tape playing. That will be one of the many challenges along the way is to keep them shielded adequately with high pass filtering.

I suppose we should stick to developing induction forges and not EMP weapons.

Last edited by B.Finnigan; 10-15-2006 at 12:15 PM.
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Old 10-15-2006, 03:04 PM
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I don't know, if you can get directional ability in an EMP weapon I can think of some good markets!

Annoying driver who won't get off the cellphone? ZAP! Lowrider with seismic bass booster cruisin' the block? ZAP! Loud music next door? Well, you get the picture.

I thought about doing just that in college, well before I got into forging, but while I could've taken out the electronics of the whole dorm I couldn't make it directional.
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Old 10-15-2006, 03:36 PM
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Brent,

Sounds good. Just wondering on the reasoning, esp since it appears that high freq is better for small amounts of metal, where low freq is better for mass melts.

I also think that Dan's workshop has the right idea on using mosfets instead of SCRs. Maybe when I get through the project at work that is killing me, I can play a little on this also. Would be fun, and a good upgrade to the shop.

Alan, I have seen a few hypothetical devices that would be directional. Would be satisfying wouldn't it!

--Carl


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Old 10-15-2006, 06:58 PM
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The more people playing around with this the better. That is probably how propane forges got to were they are now, alot different minds at work tinkering around and perfecting it.


This is a solid state home built unit that appears to be much cheaper. The site has some great info.
http://www.richieburnett.co.uk/indheat.html

This website has some additional info.

Since it uses rising and collapsing magnetic fields ferrous metals work very well. That is until the curie point (non-mag) is reached then it becomes much less efficient. In the world of physical science it seems there is always a trade off or compromise that has to dealt with.

Last edited by B.Finnigan; 10-16-2006 at 12:00 PM.
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Old 10-24-2006, 11:50 AM
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I just got the HV capacitors and should have it together within a few days. Whether it works or not I will post all of my observations and try to get a few pics. Hopefully there won't be any human lightning rod events to report on.

Last edited by B.Finnigan; 10-29-2006 at 08:58 PM.
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Old 10-24-2006, 12:36 PM
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By the way guys, if you are building these with mosfets, you might be able to get some of your parts for free as samples from manufacturers like Texas Instruments and the like.


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Old 10-24-2006, 12:54 PM
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Just found this also

http://www.fairchildsemi.com/an/AN/AN-9012.pdf

Looks to have some good info.

Need to sign up and get the notes here

http://www.ameritherm.com/technotes.html

Seems to have good info on coil design, but need to sign up to get the note.

--Carl


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