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Mcgyver
11-30-2017, 04:18 PM
With many, the majority perhaps, of resistance soldering rigs, one side of the work is connect to one side of the circuit, and connection is made to the other with a carbon probe permitting a low voltage high amp current to flow. I grabbed a gouging rod and could hack apart some batteries....but wonder exactly what the roll of the carbon is

The carbon probe has the advantage that it won't solder or weld itself to the work. It also gets hot, red hot sometimes, because of its resistance.

My question is, does the heat of the carbon rod do anything, or is carbon just used because it won't attached itself? if you made one with the plan to connect both sides of the work solidly and controlled duration with a switch (vs touching off with the carbon rod) would it work as well?

Thanks for any insight.

RB211
11-30-2017, 04:21 PM
With many, the majority perhaps, of resistance soldering rigs, one side of the work is connect to one side of the circuit, and connection is made to the other with a carbon probe permitting a low voltage high amp current to flow. I grabbed a gouging rod and could hack apart some batteries....but wonder exactly what the roll of the carbon is

The carbon probe has the advantage that it won't solder or weld itself to the work. It also gets hot, red hot sometimes, because of its resistance.

My question is, does the heat of the carbon rod do anything, or is carbon just used because it won't attached itself? if you made one with the plan to connect both sides of the work solidly and controlled duration with a switch (vs touching off with the carbon rod) would it work as well?

Thanks for any insight.
I think you should conduct an experiment, and show the findings to all of us.

Mcgyver
11-30-2017, 04:28 PM
I think you should conduct an experiment, and show the findings to all of us.

I'd guess heat from the carbon does very little as the rigs do work without. The post was because I'd rather heed the voice of experience than make every mistake first hand

RB211
11-30-2017, 04:31 PM
I understand, but making mistakes is how one learns. For the record, I know nothing about this subject, other than my CF drone heating up due to a short

J Tiers
11-30-2017, 04:59 PM
http://resistancesoldering.com/site/faq

https://www.micromark.com/Instructions/85522-resistance%20soldering-inst.pdf

http://www.raymondwalley.com/misc/tools/rsu.html

Mcgyver
11-30-2017, 05:06 PM
I understand, but making mistakes is how one learns.

Not this one. I'd prefer to only learn by mistakes when necessary. Aren't you a pilot? :)


Geez Jerry that was almost an OT.....lol....but I confess that last link was one I missed and quite good, thanks

RB211
11-30-2017, 06:44 PM
Not this one. I'd prefer to only learn by mistakes when necessary. Aren't you a pilot? :)


Geez Jerry that was almost an OT.....lol....but I confess that last link was one I missed and quite good, thanks

The important thing is that you donít repeat mistakes, the ones you survive :)


Sent from my iPhone using Tapatalk Pro

Rich Carlstedt
11-30-2017, 08:15 PM
The Carbon Rods are not there to heat up, but to provide a large cross-sectional "low resistance" area.
The low resistance should not develop heat--normally, the concept being that the two metals you are joining will have more interface resistance, and thus more heat- enough to melt lead solder ( ~ 350-600 F ).
I use either EDM rod or Carbon Arc rod in my resistance soldering unit.
Yes, D cell batteries have a carbon rod core, but they also have other metals/alloys that most likely have a higher resistance than pure carbon- and as such will grow hot in use and may not give you the Amps needed ?

For those not familiar with Resistance Soldering, its a great concept.
You have a super heavy Low voltage/ high amp transformer that is connected with heavy flexible wire. one wire to a plate of copper and the other to a hand tool ( mine is made of wood). You lay your work pieces on the copper (or steel ) plate and clamp them if necessary ( not a requirement) The hand tool can have a carbon rod or a pointed piece of stellite or carbide.
The pointed piece is for very small work ( jewelry ie) and the carbide gets hot . SO that hand tool will have cooling fins
For larger work, the carbon rod is to be placed flat on metal pieces and the Carbon/metal juncture has lower resistance than the metal/metal juncture and so the metal/metal juncture gets hotter ( per OHM'S Law)
On my unit, I can push 1.8 Volts, 2.0 Volts or 2.2 Volts at 50 Amps +

Rich

darryl
11-30-2017, 08:41 PM
I can imagine that when the carbon rods get hot, that will help to heat the junction and melt the solder. The joint itself needs to melt the solder, so you don't apply it to the carbon tips- that's a common mistake with any soldering. Many people tend to melt the solder with the iron, then apply that to the junction and end up with a cold solder joint. I like to melt a small amount of solder with the iron to assist heat flow into the junction, but then apply the solder to the junction until it wicks in. And the intermittent 'touch and go' thing is bad too- you need to apply the heat and keep it on until solder flows, then pull the iron away.

I have a resistance soldering pen, runs on AAs. Think about how few amps are going to flow, several perhaps but certainly not 50 or even 20. I think in this case the heating of the tips is helping to do the job. They call this a cold soldering pen- probably good for making cold solder joints :) I never use it.

GNM109
11-30-2017, 09:39 PM
I built my resistance soldering unit some 30 years ago. It uses a typical 1/4" carbon rod that is copper coated. The current flows into the work between the carbon rod and the ground. The reasons for a carbon rod is that it conducts heat and electricity nicely and after the current is shut off when the joint is made, if held in place, it will cool the joint very quickly.

I used a 10 amp center-tapped transformer for mine. It was formerly powered with a Variac, but the one I used burned out after many years so I switched to a large light dimmer with good results. I also used a foot pedal to start and stop the current.

There are some units that utilize tweezers that have both the power and the neutral or ground side but I'm not familiar with those.

I've used my unit on my model railroad primarily for soldering small brass parts together. It works beautifully.

livesteam
12-01-2017, 12:10 AM
I too built my unit using a transformer intended for scratch marking on metal, tools, etc. Very low V and high current.
The electronics manufacturing plant I worked in had the American Beauty units. I copied the design of the handpiece
tweezer at first using D cell carbons, but they were too soft. Installed copper coated arc rods and still have them
after over 30 years. Great for soldering large electrical contacts and small metal assemblies. It allows a clean job as
no contact is needed with the actual solder area. It's a combination of high current thru the part soldered and heat
at the carbon contact tip which is usually a rounded point. I have silver brazed small assemblies as well. There are
or were metal alloy tips available for small work.

JRouche
12-01-2017, 01:11 AM
Resistance Soldering carbon probes - are you experienced? .

No. Sorry Mak. No experience that I have.

Look, a question asked and and answered. :) JR

danlb
12-01-2017, 02:16 AM
I have a resistance soldering pen, runs on AAs. Think about how few amps are going to flow, several perhaps but certainly not 50 or even 20. I think in this case the heating of the tips is helping to do the job. They call this a cold soldering pen- probably good for making cold solder joints :) I never use it.

That sounds like the "Cold Heat" soldering system. Their web page says that it generates heat in the tips, not necessarily in the joint that you are soldering. I believe that means that it's not resistance soldering.

Interestingly, the cold heat system does work OK in many cases. Handy for fixing broken wires in hard to access spots.

Dan

garyhlucas
12-01-2017, 01:49 PM
You guys have this all wrong. NONE of the heat comes from the joint resistance. ALL the heat comes from the carbon resistance. The joint is an extremely short conductor with very low resistance so the voltage drop across that resistance is also very small. Therefore Watts = Current x Voltage drop is almost nothing. Hence the high resistance of the carbon is what is generating the heat. If this were not true a copper rod would work much better and all you get with a copper rod is a dead short.

J Tiers
12-01-2017, 02:05 PM
If you look at some of the pics and videos, the carbon tip is often red or orange hot.......

GNM109
12-01-2017, 02:13 PM
You guys have this all wrong. NONE of the heat comes from the joint resistance. ALL the heat comes from the carbon resistance. The joint is an extremely short conductor with very low resistance so the voltage drop across that resistance is also very small. Therefore Watts = Current x Voltage drop is almost nothing. Hence the high resistance of the carbon is what is generating the heat. If this were not true a copper rod would work much better and all you get with a copper rod is a dead short.

Yes, it does work nicely with a carbon rod. I notice that the copper-plated copper rods work best with the plain carbon rods not so much. Ive never used anything other than the carbon rods. I never thought about the theory before.

garyhlucas
12-01-2017, 06:10 PM
Yes, it does work nicely with a carbon rod. I notice that the copper-plated copper rods work best with the plain carbon rods not so much. Ive never used anything other than the carbon rods. I never thought about the theory before.

Yes the copper coated work best because the voltage isn't dropped by the long length of carbon resistance so all the heat gets generated in the short piece of carbon at the end.

Mcgyver
12-02-2017, 09:38 AM
You guys have this all wrong. NONE of the heat comes from the joint resistance.

Have a look at this, starting at about 1 min. https://www.youtube.com/watch?v=JVao0vmBMOI

This isn't very scientific, but it looks like its from resistance between work pieces as the carbon rod doesn't seem to heat up much yet the copper is very quickly at solder temps - . I'm surprised at just how well it worked, given the area contact and low resistance of copper. plus I'm sure I've seen them in use without carbon rods. I thought what was happening was similar to a spot welder, like Rich says "interface resistance"

It seems a lot of guys make resistance solderers from 12V DC charging transformers, and there is also talk that it works well with brass but not so much with copper (because of its lower resistance). Seems the obvious then is it needs to be a lower voltage.....1 or 2. I might dig out the rewound sodium light ballast I made for the spot welder attempt, it's at 1.5v iirc

garyhlucas
12-02-2017, 07:33 PM
Spot welders use heavy copper buss bars with low resistance combined with thousands of amps of current through the relatively high resistance of the material being welded.

Magicniner
12-02-2017, 08:12 PM
If you haven't used a 1lb+ copper soldering iron you won't understand their speed and efficiency in soldering big heavy joints very quickly and with the least energy and heat applied to the components being joined ;-)

J Tiers
12-02-2017, 08:58 PM
If you haven't used a 1lb+ copper soldering iron you won't understand their speed and efficiency in soldering big heavy joints very quickly and with the least energy and heat applied to the components being joined ;-)

Last time I needed t solder patches on some copper guttering at the house, I tried the soldering coppers. I ended up using a torch, the coppers just could not keep up with the heat loss. I had two of them, and needed 4, so three would be heating at any time. One would get too cold before the next was hot.

I consider myself pretty good at soldering, but that copper gutter was sucking away heat way too fast to work with what I had. Terne plate might have been easy enough, though.

Mcgyver
12-02-2017, 09:10 PM
Spot welders use heavy copper buss bars with low resistance combined with thousands of amps of current through the relatively high resistance of the material being welded.

I know, I've got one, and prior to did a bunch of work understanding there operating principals trying to make one. With about 2000 amps irrc it worked but just didn't get enough amps to work well. Its not clear to me why the same principal can't apply to solder. A volt or two, high amps, why wouldn't work temps will rise, especially if its a reduced cross section where they meet? The reports are that brass is easy, copper difficult.....which suggests it is by resistance in the work. In that video, did you think the copper heated up that quickly because of the tiny red glow on the carbon?

I'm sure I've seen resistance soldering examples without the carbon....can't place where though. I'm not trying to argue - I'm unsure of all this.... so not saying your all wrong, but the video I put up makes a bit hard to buy its "just the heat from the carbon"

J Tiers
12-02-2017, 09:26 PM
It is the resistance of the material for sure.... but the carbon was clearly even hotter than the metal, which had to be contributing something....

Copper has a double whammy, similarly to aluminum, which is hard to spot weld. Not only is it low resistance electrically, but it also conducts heat away from the joint quickly and well.

So copper will get hot poorly , and get cold very easily......

Mcgyver
12-03-2017, 06:45 AM
It is the resistance of the material for sure.... but the carbon was clearly even hotter than the metal, which had to be contributing something....

.

thats what I thought, but given I have no first hand experience.......anyway, ideally I like to solder copper pins vertical to a surface (watch dial feet). I think I'll shoot for a volt or two (vs the the common 12V diy make from car battery chargers) and turn a large angle cone on the end so there is a small cross section at the point of contact.

GNM109
12-03-2017, 10:06 AM
If you intend to do some small resistance soldering, say for model building like I do or for fine work on Jewelry, it pays to have a source for solder-bearing paste flux. A small dab in between the parts to be joined is all that's needed. Then, when heat is applied with your resistance unit, the parts will instantly join.

I always hold the carbon point on the joint for an instant after letting up the foot pedal and it draws the heat right back out.

By the way, I have tried using a stick of TIG Tungsten to replace the carbon with no results. It didn't work at all. The carbon is best IMHO.