Resistance Soldering

JohnSol

JohnSol

Registered
Country flag
A couple solder joints on my Accucraft C&S 60 failed. I tried fixing them with a 250 watt soldering gun. The results were disgusting. Soldering on these models is tricky business.

Recently, I've been experimenting with Resistance Soldering. I've tried different power units, probes, tweezers and electrode materials. At this point I'm on the low end of the learning curve. My last test involved a modified probe. Originally a wire stripper with two leads to the power unit, I removed the internals and machined a brass holder for a five millimeter carbon electrode (see attachment.)004.JPG Testing with different shaped carbons at wattages ranging from 130 to 250 on small .020" thick brass squares and tubes yielded results that ranged from damaging the brass to good joints with the solder melting almost instantly.

Obviously, I'm nowhere near the needed proficiency to work on brass models. Outside of continuous experimentation, is there any guidance for soldering and repairing brass models?
 
I've been using a Wassco 250 watt unit. I also have this American Beauty 1000 watt unit (see attachments.) As of now. The small American Beauty tweezers I have were too light, as was the American Beauty probe with the .060" stainless electrode. Neither of which are pictured. The probe with the five millimeter (.200") carbon electrode seems correct. The problem I'm having is control of time and heat. I did find out that both ground and electrode need to be as close to the joint to be soldered to avoid heat to the adjacent soldered parts. The resistance soldering tools are very effective in this regard. Outside of the area between the ground and the probe, there is negligible heating.001.JPG005.JPG
 
The problem with soldering brass is that it is a good conductor - too good, so the heat dissipates through the material

The way that I was taught was to use a lower melting point solder - 145 degree solder is reckoned to be one of the most suitable.

Then you need a liquid flux. The difficulty here is that effective fluxes are a bit acidic, and sometimes will need some neutralisation after the solder joint is run. It depends on what is available on your side of the pond; you may be able to get a liquid flux that is not too aggressive, and can be simply washed off after the joint is run. The manufacturer's information sheet will provide the necessary details.

I have made a couple of brass models in the smaller scales, and my snow plow is made from brass.

My yellow and blue 6w diesel loco was an etched kit made by Worsley Works, but they suggested nickel silver for this scale as the heat dissipates less and it is easier to solder. I still used the 145 degree solder, and the joints ran well.
 
John Solimine said:
solder joints on my Accucraft C&S 60
Click to expand...
I simplified the air piping on my RGS C-19, as EBT #7 only had one air pump, and no electrics. The Accucraft brass pipes were all soldered together with little 90 deg castings, t-junctions, etc. It was (almost) impossible to solder one piece without the rest falling apart.
And don't ask about the C-16 cow-catcher that I shortened. Each bar was individually soldered - they must have had a jig. I had to make a jig to put it back together!
 
Last edited:
Fred2179G said:
I simplified the air piping on my RGS C-19, as EBT #7 only had one air pump, and no electrics. The Accucraft brass pipes were all soldered together with little 90 deg castings, t-junctions, etc. It was (almost) impossible to solder one piece without the rest falling apart.
And don't ask about the C-16 cow-catcher that I shortened. Each bar was individually soldered - they must have had a jig. I had to make a jog to put it back together!
Click to expand...
Yes, if it's a question of adding details to a brass pipe, or brass fitting, then use a heat sink - like a pair of grips to ensure that the unwanted heat doesn't travel too far down the length of brass.

Other fine details can be added with lower temp solder - 85 degree solder is used for white metal ( and that was before they took the lead out :oops::oops: ) and can be used to solder cast details to brass. This type of solder may need a different liquid flux.

But, as Fred says, when you're dealing with manufactured locos, it can be a bit of a different matter, and you may not be able to undertake a full solder repair as I suspect that a large proportion of the model would have been set in a jig before soldering.
 
I find the easy way to go about soldering expensive models is, get some who's an expert in the craft!
 
Thank you for sharing your personal experience.

Rhinochugger, you mentioned that you constructed some smaller scale models. What heat source and solder did you use?

As of today, 60 / 40 Rosin core is the only solder that I've tried. I'll try silver solder with the appropriate acid flux next.

The major benefit I found with using the carbon electrode is the ability to shape it to mate the part that will be soldered... it seems to be all about heat transfer. As I mentioned before, if the ground and electrode are close and on opposite sides of the joint to be soldered, the heat is so fast, local and intense that it barely conducts heat beyond the joint being soldered. I'm not sure about controlling the latent conductive heat. It may require heat sinks. Or as Fred mentioned, there may be no alternative to using jigs.

I'll post the results of my next test session.
 
I just YouTubed ‘resistance soldering unit’ and found a lot if help in that search, not only making but using for big loco kits. Perhaps a look at some of them and report back to us your success? I did have the opportunity to have a commercial modelers one foc when my mate sadly died, I never took it up and at times now I wish that I had.
 
I have never used resistance soldering, however when I was a member of the Gauge 0 Guild, it was used by a number of their members, as it seems 0 Gauge modellers make a lot of brass kits. Raymond Walley has an article on his website Resistance Soldering
 
John Solimine said:
Thank you for sharing your personal experience.

Rhinochugger, you mentioned that you constructed some smaller scale models. What heat source and solder did you use?

As of today, 60 / 40 Rosin core is the only solder that I've tried. I'll try silver solder with the appropriate acid flux next.

The major benefit I found with using the carbon electrode is the ability to shape it to mate the part that will be soldered... it seems to be all about heat transfer. As I mentioned before, if the ground and electrode are close and on opposite sides of the joint to be soldered, the heat is so fast, local and intense that it barely conducts heat beyond the joint being soldered. I'm not sure about controlling the latent conductive heat. It may require heat sinks. Or as Fred mentioned, there may be no alternative to using jigs.

I'll post the results of my next test session.
Click to expand...
I was using a standard 50 watt soldering iron, 145 degree solder (standard resin cored solder is usually 220 degree melting) and liquid flux (Carr's product).

I must admit that, being a Luddite and devout bodger, I've not gone into the technicalities of resistance soldering. I don't have any piccies of the smaller models as they were before digital photography, but the nickel silver blue and yellow diesel which is all soldered by the same method is here.

At the last house, this loco took a 2 ft plunge off the track onto a concrete paving slab - and largely survived. I put it down to the nickel silver having a bit of flex, and the soldered joints holding firm - it's still running, only about to be named Yeti, as in yetinother gearbox - this time a rather more robust, elaborate and more expensive quality item :emo:

PICT0015-001.JPG
 
Gained more insight from YouTube. The link JimmyB posted was a good explanation of what's being used in the UK (Europe.) However, I was left wondering if the output of the UK power source was AC or DC current. Both the U.S. made Wassco and American Beauty power sources are AC. Therefore, I believe the probe and ground can be switched with no effect (or is some kind of reverse polarity a possibility with AC current?) The difference between the explanation that JimmyB posted and the techs at American Beauty is... the American Beauty techs suggest using the probe on one side of the piece to be soldered and the ground on the other. The gap between the two pieces develops the greatest resistance and subsequent heat.

And... that looks like a professionally made model Rhinochugger. Very clean looking joints.

*****************************EDIT***************************

I need to find a source for soldering paste before I continue. There's much to learn
 
Last edited:
John Solimine said:
Gained more insight from YouTube. The link JimmyB posted was a good explanation of what's being used in the UK (Europe.) However, I was left wondering if the output of the UK power source was AC or DC current. Both the U.S. made Wassco and American Beauty power sources are AC. Therefore, I believe the probe and ground can be switched with no effect (or is some kind of reverse polarity a possibility with AC current?) The difference between the explanation that JimmyB posted and the techs at American Beauty is... the American Beauty techs suggest using the probe on one side of the piece to be soldered and the ground on the other. The gap between the two pieces develops the greatest resistance and subsequent heat.

And... that looks like a professionally made model Rhinochugger. Very clean looking joints.

*****************************EDIT***************************

I need to find a source for soldering paste before I continue. There's much to learn
Click to expand...
Very kind of you to say so, John.

When I made it, I knew that the camera would do me no favours, so I had to curb my natural impatience. I held the corners with blue tack, then spot soldered. Only when I was happy that the alignment was perfick, did I run the solder down the entire joint.
 
Update on Resistance Soldering;

There's a source for high quality solder in small amounts from H&H Electronics H&N Electronics Soldering Flux . This is a small U.S. (California) based supplier dedicated to hobbyists.

Note: Certain fluxes, i.e., aluminum flux, can only be shipped by ground.
 
You must log in or register to reply here.
Back
Top Bottom