Electrical Resistance Forge...

J

J.S. Carter

Joined
Jul 4, 2007
Messages
915
K, my cars cigarette lighter got me thinkin today,(yea I'm easily amused...:rolleyes:)how easy, (and or) feasible would it be to build an Electrical Resistance Forge, (think of the stove top burners they get red really fast) I think it would probably be more economical to operate and have a greater temperature control, using an old fashioned dimmer switch, to control the flow. I propose that you would lay your work on a rack of some sort to complete the circuit. then turn on the juice to induce the heat, after getting to temp, shutting off the electricity to remove the work to the anvil just like you do your old squirell cage blower on the old coal forges. Any ideas on designs and how to build such a cool thing? Maybe utilise a kick / foot switch to cut the juice before removing the piece from the current,
 
The ones from Blacksmith supply are induction heaters. No contact is involved and it operates COMPLETELY differently from your stovetop. That said, they're VERY cool and I wish I had one :D

-d
 
The bad news is that you can't use a dimmer switch. It isn't made for the power, current or voltage for this kind of operation. 110V coming out of your regular wall outlet isn't going to supply enough power. What you want is to convert an electric oven and plug it in where you plug in your electric oven---to high current 220V. In case this doesn't intimidate you, it should.

I don't know how high a temperature the oven heating elements will tolerate, but if you could replace the oven box with a smaller enclosure insulated with fire brick the elements would get hotter than normal (they couldn't shed as much heat as usual). They probably tend to self-limit in temperature. As they get hotter their resistance increases and that limits the current that will go through them. You might be able to find some industrial furnace heating elements. If these had the same current limit, but were smaller in size they would reach a higher temperature without overloading the oven switch.

This is all really hard and dangerous. The big difficulty is the temperature and the current. To handle the high current you need thick wire and really good connections. The connections are likely to get too hot to use solder or things like wire nuts. It gets too hot for ordinary wire insulation. You need to really bolt the connections together and insulate things with ceramic or similar fireproof material. If a connection is not really, really good the connection will heat as much or more than the heating element. It will fail catastrophically. As it self heats it will get more resistive which will make it heat up more. It is likely to burn out in a sudden flash of molten and burning metal.

So while you might make one from some salvaged oven parts and maybe industrial heating elements it would be a real fire hazard. You would also need a place to plug it in to a high current 220V outlet where you don't have to worry about it burning the house down. It starts to make gas look good.

The commercial induction furnaces do a real clean job if you can afford to buy one. They will selectively heat up your steel rather than the rest of the oven components. They don't leave a residue.

Be safe.
 
the problem with passing power through the blade is that the blade has very little resistance. the burners on a stove are around 25 ohms at 240v thats 8-9 amps it pulls. the blade has next to nothing like .001 ohms maybe and at 240 volts that would pull 240,000 amps. that would cost you in power charges around $5,184 an hr to run at .09 a KW hr. :D not to mention how you would get that much power.
 
Thanx guys! I appreciate it and will continue to study this, Jarod, i know i said "complete a circuit," but the way it would work in my head is to have 2 power lines, one positioned at the tip the other at the butt and let the electrons crash into each other somewhere in the middle to create the resistance, very similar to your toaster, or dryer heating element, etc etc
I have 220 hook up available, :D so that wont be a problem I will be SAFE I am a steward in the IBEW so i do have some background in electricity... again thanx guys i really appreciate your help!
 
Not what would happen. The crashing thing. Electricity flows from negative to positive. If you hooked up 2 10,000 volt positives to one blank nothing would happen no flow no crash equal potential
same with 2 negatives no flow no crash equal potential
same with 2 in phase AC supplies no crash no flow equal potentials
1 positive and 1 neg or 2 ACs out of phase and whamo flow the amount of flow (amps) the amount of amps is voltage (V) divided by resistance (ohms). The amount of power (watts) is amps X voltage or Ohms law of electrical power P=IxE and its associated law V/ohm=A
The resistance is in the piece from jump street. Adding electricity will not add resistance unless the pieces resistance changes as it heats or something like that. Also the sections of the piece with the smallest volumes would have more resistance and heat more than large sections. IE a 3/8 tang would have mare resistance than a 3/16 x 1 1/4 blade area. So it would heat way faster. The way a toaster or oven works is the elements have quite a bit more resistance to the flow of power so they heat up as the electrons work at flowing back and forth (AC). NO CRASHES. If the resistance wires were not uniform along their entire length the major portion of the heat would occur at the highest resistance area and either burn that area out or if the resistance is to high slow the flow to the point little happened unless more voltage was applied. If I take and make a loop of say 12 gauge wire and put a nick any where along its length and the apply power to the ends and begin ramping up the voltage applied the nick (were the higher resistance is will heat before the rest of the wire and as the voltage is increased the wire will burn out at the nick. I am not in the IBEW but, I did get straight As for 2 years in college in electronics.

As stated before inductance is a different deal much like the way a transformer works. If you were to place the blank inside a coil and energize the coil and have leads attached to the blank and a load on the leads you might start to do something

That bang and flash of light you see when a line blows apart due to a dead short isn't a crash it is the power of the voltage as it jumps the resistance of the gap created in the wire when it melted. ARC once it melts enough away that the resistance is to large to bridge by that voltage it stops
 
electrical resistance forge = kiln
the only way you are going to have electrons crashing into each other is in a supercollider
electrons have a negative charge, thus repel each other in the same way as 2 north poles of a magnet do but a whole lot stronger. Basic physics, That's why a wire will do most of its work at the surface (which is why you can put large amounts of current in surprisingly thin runs on a printed circuit board), I don't have the knowlege to check JT's math but he's basically correct, as is Jeff Clark and ib2v4u
I tried using a kiln for forging, not worth the electric bill, long cycle time, and decarb. Use an electric kiln for heat treating use fire for forging.

-Page
 
A little studying of basic electrical theory will show you why this won't work.
Stacy
 
yea your right guys... did some more digging, asked some of the older electricians, told me the same you guys just did, see this is why i come here, ya'll set me straight when i get half brained ideas...

Thanx again
 
Just talking out of my hat here because what I know about electrics is confined to home electrical wiring.

Resistance or spot welding equipment might be a possibility. You would probably talking about 660V equipment and 3 phase power.
 
Stick with home wiring. The difference between a resistance unit and a spot welder is night and day. You are right that the power required ,if it were possible, would be HUGH.
Stacy
 
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