# Resistance Soldering?



## alfischer (Mar 8, 2010)

I am convinced that resistance soldering is the best solution for track work and many other things. However using a carbon rod type of probe seems at best cumbersome. Holding the part in place while kneeling upside-down on a layout while having only two hands is difficult. I see tweezer type probes are available. Look like a good solution but seem pricey. Anyone using tweezers for this? What have you found to be the best practical solution?


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## Jack - Freshwater Models (Feb 17, 2008)

I have used tweezers but they are really for very small parts. I mostly use copper clad carbon rods that are sharpened with a file hooked up to a home made sildering rig. I can do most the resistance soldering I want to do using the plain carbon rod. Pliers can be found at http://www.micromark.com/Resistance-Soldering-Equipment.html but I have no experience withthem. They have good size chunks of carbon which will provide more heat than the tweezers. A simpler/cheaper solution might be to make a clamp to hold the carbon rod to the rail so that you only have to handle the solder and flux. 

Jack


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## SE18 (Feb 21, 2008)

I saw them in a MM catalog; can get pricey with the good ones up to $500 or so. I read somewhere how to make one and have it on my 10-year-from-now-2-du-list; The MM advantage, it seems, is that you can dial up numbers, therefore, if working on, say, a brass loco, you can dial up a big # and solder the big part, then dial down as the parts get smaller, avoiding the already soldered parts from falling off. 

Without a resistance soldering device, I'm not sure how folks on this forum and others work in close quarters, unless they are really experts with heat sinks; also, I think they have different solders and fluxes that have different heating points, but the resistance soldering setup seems to easiest to use if you lack a knack or experience 

correct me if I'm wrong, please 

Dave V


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## Dean Whipple (Jan 2, 2008)

*http://4largescale.com/trains/P20.htm*
at the bottom of the page - Building a resistance solder tool


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## Jack - Freshwater Models (Feb 17, 2008)

In the old days a lot was done (and still is) with a simple soldering iron. Wet rags and lumps or metal cqan be used as heat sinks. A lump of sal-amoniac is used for cleaning the iron. I still use an iron for wiring but use a torch and home made resistance unit for other work. 

You could buy some plier electrodes and make your own pliers. 

Jack


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## Greg Elmassian (Jan 3, 2008)

Resistance soldering jumpers on brass track is the nicest way, no excessive heat to melt ties, or trying to heat sink it and get the rail real hot at the same time. 

If you could find a used one by miller engineering, that's a nice one, and heavy enough to do rail easily. 

Regards, Greg


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## xo18thfa (Jan 2, 2008)

Posted By Dean Whipple on 11 Aug 2010 10:29 AM 
*http://4largescale.com/trains/P20.htm*
at the bottom of the page - Building a resistance solder tool



This is another "unstarted" project.


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## alfischer (Mar 8, 2010)

OK. Sounds like the tweeezers are not what is best fir track. I built one of these puppys but it's a bit cumbersome to use. Had a transformer about 6V that is good for about 50 amp. Put a 1kw variac (vintage about 1940) on it and a foot switch. Old pencil iron holds the carbon. Works, but carrying it around is baaad! Impossible to use foot switch while kneeling in ballast. Fine on a table. Overbuilt? Yep. Had everyting except the footswitch. 

What I want is a button on the handpiece instead of the footswitch. Back to the drawing board...


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## Dean Whipple (Jan 2, 2008)

Posted By xo18thfa on 11 Aug 2010 06:34 PM 
Posted By Dean Whipple on 11 Aug 2010 10:29 AM 
*http://4largescale.com/trains/P20.htm*
at the bottom of the page - Building a resistance solder tool



This is another "unstarted" project.


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## alfischer (Mar 8, 2010)

You mean I am not the only one with a list of unstarted projects? Problem is I also have a long list of started and unfinished projects! I need spreadsheet for each list!


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## Matt Vogt (Jan 2, 2008)

Al, it sounds like you have a similar setup to the one I built from George Schreyer's instructions. I built my own 'tweezers' to hold two carbon rods about an inch apart out of oak. I made them pliable enough to squeeze them together for smaller work. I also installed a ground lead with an alligator clip. For a lot of work it's more convenient to attach this and remove the ground carbon rod and use the pliers or tweezers this way- with just the positive rod. I wish I could show you pictures, but haven't taken any yet... I'll try to post some soon. 

As far as replacing the foot pedal with a button, it may be hard to find a button that will take the current, but I'm sure you'll find one if you look hard enough. 

Keep us posted,
Matt


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## alfischer (Mar 8, 2010)

Currently the footswitch controls a relay on the primary side of the transformer. The button could do the same. I am considering redoing the whole thing with a MUCH smaller and lighter transformer. My unit weighs about 25 pounds. I guess I don't understand a commercial unit being rated for 250 watts as small as it is. Have a friend that bought one and I am going to measure the volage and current and weight mor out of curiosity. Don't understand how a 12v 10a battery charger can handle the job of a 250w unit.


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## SE18 (Feb 21, 2008)

out of curiosity, does anyone who owns a resistance soldering setup do hard-soldering with it? Also, would there be an additional need to use the small butane torch in certain applications where a resistance soldering device would not work as well?


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## Jack - Freshwater Models (Feb 17, 2008)

Posted By SE18 on 12 Aug 2010 04:50 AM 
out of curiosity, does anyone who owns a resistance soldering setup do hard-soldering with it? Also, would there be an additional need to use the small butane torch in certain applications where a resistance soldering device would not work as well? I have heard that silver soldering can be done with resistance but it would take a lot of power (big carbon) to get the part to temperature. I mostly use a propane torch, home made resistance unit and an iron. For boiler work I use a acetelyne. I probably use a torch the most for soldering. Resistance soldering really shines when doing work in sheet brass and other light parts.

Jack


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## alfischer (Mar 8, 2010)

What size transformer did you use in your homemade unit? How long to solder a jumper to a "G" rail? What size carbon rod?


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## Jack - Freshwater Models (Feb 17, 2008)

Posted By alfischer on 12 Aug 2010 01:58 PM 
What size transformer did you use in your homemade unit? How long to solder a jumper to a "G" rail? What size carbon rod? 


Voltage is not critical and anywhere between 4-12v will work. What you do need is amperage and I would suggest 20amp or more for the transformer. I have a 5V -50amp and a 5v - 30amp both purchased years ago surplus.

I have found that a trip to the local welding supply yields useful copper clad carbon electrodes in 1/8" 3/16" and 1/4" diameters. For track I would use the 1/4" electrode . The solder should melt in maybe 10seconds???

Resistance soldering is something you need to play with a bit to get the feel of how to do it.

Jack


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## alfischer (Mar 8, 2010)

Interesting. I doubt the $400+ units being sold for trains have that much amperage rating. They CLAIM 250 wats but a 250 wat transformer weighs much more than these pricey units. I figured at least 20-30 amps would be needed. Don't understand taking a 10 amp battery charger and using it's transformer. It's probably over rated for 10 amps to start with. The one I built is a heavy monster. Used the transformer for my old 8080 system (vintage 1980) and the current rating was well over 50 amps. It's really to big and heave for convenient use.


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## xo18thfa (Jan 2, 2008)

Posted By Dean Whipple on 11 Aug 2010 09:01 PM 
Posted By xo18thfa on 11 Aug 2010 06:34 PM 
Posted By Dean Whipple on 11 Aug 2010 10:29 AM 
*http://4largescale.com/trains/P20.htm*
at the bottom of the page - Building a resistance solder tool



This is another "unstarted" project. 














Yes, "unstarted" projects. They are like "unfinished" projects that have not been started yet. I saw this article a while back and it's on the "to-do" list, along with a 100 others.


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## Jack - Freshwater Models (Feb 17, 2008)

Posted By alfischer on 12 Aug 2010 04:17 PM 
Interesting. I doubt the $400+ units being sold for trains have that much amperage rating. They CLAIM 250 wats but a 250 wat transformer weighs much more than these pricey units. I figured at least 20-30 amps would be needed. Don't understand taking a 10 amp battery charger and using it's transformer. It's probably over rated for 10 amps to start with. The one I built is a heavy monster. Used the transformer for my old 8080 system (vintage 1980) and the current rating was well over 50 amps. It's really to big and heave for convenient use. 10amps might work OK on smaller stuff. Most RS units offered to hobbyists are IMHO high priced junque. I sometimes go to local hamfests and find unworking RS units. Thats where I got my electrode holder and tweezers. 

I had heard that it was easy to build a RS unit but didn't act on it. Then I saw a picture of a work bench in a Japan brass loco factory with home built RS unit. That was the beginning of building my own.

The unit I currently use is 5V -30amp. I use a foot switch hooked up to a variac hooked to the transformer. It all cost me about $55 to have a working unit. I later added the commercial parts for another $20. A sight better than the $400+ units though it did take some effort. BTW the variac has other uses in the shop!

Jack


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## alfischer (Mar 8, 2010)

Sounds like we think alike. Haven't been to a hamfest in years! I am not about to olunk down $400-$500 on a commercial unit. Would like to build a practical and portable one. Th one I built about 3 yrs ago is capable of welding. Too big. Gonna have to get to the next electronics flea market in the Bay Area. There is nothing electronics wise available other than RS and a small local junk shop.


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## SE18 (Feb 21, 2008)

al,

good point; if you're going to fork over $500 or so for a resistance setup, might as well get yourself a real good welder, esp. if you're working in the larger scales and your work isn't too delicate


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## Jack - Freshwater Models (Feb 17, 2008)

Posted By alfischer on 13 Aug 2010 07:10 AM 
Sounds like we think alike. Haven't been to a hamfest in years! I am not about to olunk down $400-$500 on a commercial unit. Would like to build a practical and portable one. Th one I built about 3 yrs ago is capable of welding. Too big. Gonna have to get to the next electronics flea market in the Bay Area. There is nothing electronics wise available other than RS and a small local junk shop. 

You can use any type of foot switch. A good substitute for a variac is a fan speed control switch from the home improvement store. The transformer is the tough item to find though eBay may be a good bet.

Jack


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## alfischer (Mar 8, 2010)

The speed control would be preferable as it weighs less. The variac I have in mine must be over 5 lbs! It's 1kw. 

I have a good friend that spends his life doing flea markets and thrift stores that is 100% electronics knowledgeable. I need to call him and put in an 'order' for a nice transformer. He will probably find on for $5-$10. He's GOOD. Found me a couple 24v 10 amp switchers for $5 a while back. Hard to beat. 

I am not really an EBAY fan but use it occasionally with a lot of discretion.


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## maculsay (Jan 2, 2008)

Al...I built a light-duty resistance soldering unit a few years back using an 8 amp filament transformer. It works really well for my modeling tasks. See my builder's log.


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## alfischer (Mar 8, 2010)

Thanks Howard. I saw your project the other day. Nice job. How does it do on "G" rail jumpers? How long to melt the solder for them?


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