Soldering rail joints

[Dave Schneider]

Recently I have had a couple of problems trying to solder some of my rail joints, with the solder preferentially flowing to one side of the joint.  I used flux on both sides, with little success. A likely cause is that the rails need to be cleaned better before soldering. I tried using 70% isopropyl alcohol on a q-tip, and that seemed to help. More heat seems to help (ie. applied longer) but the ties are getting melted.

Any tips to share on cleanig the rails? Is the alcohol a good choice? Maybe the MircoMark scratch brush? http://www.micromark.com/scratch-brush,8058.html

Finally, I am using a 60/40 solder, as that is what I have on hand. Could this be the problem? I am using a 250 w resistance soldering unit with the tweezer electrodes. Wondering whether I should crank up the power (it is at 1/2 power now) to really blast the joint. I was a bit concerned about pitting the joint if I really fried it.

Best wishes, Dave

[jdcolombo]

I clean the rail with a wire brush in a dremel, don't use flux, use rosin-core 60/40 solder, 25-watt iron.  Never a problem, and I've probably done 500 joints over three layouts.

John C.

[davefoxx]

Dave,

I've never attempted resistance soldering, so I can't help specifically there.  But, after reading your post, it sounds like more heat is needed.  Maybe not cranked all the way up, but you need enough heat in the iron to heat the rail and joiner enough that the solder flows across all three surfaces.  I also make sure to have the chisel point on my soldering iron in contact with both rails and the joiner.  I apply the solder to the opposite side of the rail and the heat pulls the solder through.  I do use a paste flux.  If the soldering iron is hot enough, this process should only take one second or so.

If you're melting ties, the iron is not hot enough.

DFF

[Sokramiketes]

This will be easier with a standard iron. Leave the resistance iron for rail to pc board tie joints only.

[Dave Schneider]

Thanks for the suggestions. I would love to practice more, but I don't have enough <insert expletive> rail joiners as it is and they are also scarce.  Mike, why do you recommend against using the resistance iron? It is nice to just grab the joint and hit the pedal. Do you think that the tweezer electrodes are too small or something?

Best wishes, Dave

[mmagliaro]

I only use conventional soldering, so I can't help you on that one.
But I have never found alcohol or any liquid cleaning to be sufficient.   Scratching back and forth along the side of the rail
with a jewelers file is what I do.  Then, no matter where the solder starts to flow, it quickly and neatly spreads
across the whole joint and down into the joiner.

[DKS]

One problem using a resistance iron on a rail joint is that you have three pieces of metal that all need to be heated together. Resistance soldering tends to focus the heat at the one small point between the tips.

Also, liquid solvents are ineffective at cleaning metal for soldering, for the most part.

My best advice: clean both sides of the rail ends with a scratch brush. Keep at it until the metal is shiny. I use electronics-grade rosin-core solder and a small wedge-tipped iron; a temperature-controlled iron is best. Be sure the tip is clean (wet sponge) and tinned (bright and shiny). I use liquid acid flux, applied in tiny amounts with a fine brush, but there are a number of other options--electronics paste flux works, among others.

A small bit of solder applied to the iron tip just before placing it on the joint will help conduct heat faster. Place the iron tip at the point where the rails meet, so you can heat both rails and the rail joiner all at once. When the joint begins to sizzle--in about one second--apply solder to the opposite side of the rail from the iron; you should see the solder quickly flow along the length of the joiner on both sides. The joint should take no more than about two seconds to complete. If it takes longer, then the metal is likely not clean enough, or the iron not hot enough.

[chicken45]

What temp do you have your iron set to?

[DKS]

Typically I set it to around 300 C. Solder melts at a lower temperature, but you need a reserve of heat to bring all of the metal up to the melting point of the solder. A small wedge tip can hold sufficient heat for a typical rail joint or electrical connection.

[Sokramiketes]

Thanks for the suggestions. I would love to practice more, but I don't have enough <insert expletive> rail joiners as it is and they are also scarce.  Mike, why do you recommend against using the resistance iron? It is nice to just grab the joint and hit the pedal. Do you think that the tweezer electrodes are too small or something?

Best wishes, Dave

What David said... The resistance unit will concentrate the heat... Until you leave it on for awhile and the heat spreads too fast and melts the ties.  It can be done with practice but a regular iron is much more forgiving for this task.

[nkalanaga]

Most of my joints were in flextrack or at turnouts, many of which I prebuilt and stockpiled.  The rail ends usually had to be trimmed, so I got everything clean with a knife-edge file, while also cleaning the cut left by the rail nippers.  I'll agree that alcohol does nothing for cleaning metal except remove some of the oil and grease.  It doesn't affect oxides at all.

Some I used ancient Radio Shack paste flux on, some I used no flux.  The fluxed ones may have been a little easier, but if you don't have it, or want to use it, you'll be fine.

[robert3985]

Soldering rail joints shouldn't be a problem with proper soldering technique.  I don't solder joints with my American Beauty 250 watt resistance soldering station, I use my old Archer 35 watt iron, with it's 20 year old wedge tip and things go great.

The reason things go great is because of the flux I use, which is Superior Supersafe No. 30 Soldering Flux gel, which will make problems like yours simply disappear. 

I also don't use a lead solder anymore, but a 96/4 Tin/Silver coreless solder.

As has been said, keep your iron tip clean and tinned so it'll transfer heat efficiently to the metals of your joint.

If you've got problems with melting ties, you should cut the spacer between the ties and move them away from the joint...then when you're finished soldering and the joint is cool, move the ties back into position.

I apply heat to the outside of the rails (after I apply a little drop of Supersafe Flux), centering the rail joiner on my wedge tip with the junction of the rails centered on my tip...then I apply solder to the opposite side of the rail web and the surface of the rail joiner.  When the solder melts, take the solder off and what has melted will flow towards the iron, completely wetting the inside of the rail joiner along the foot of both pieces of rail.  That's all that's necessary as you don't want a big blob of solder on the joint.  This goes really fast, and the heat generated is not excessive for the joint to form.  Take the iron off the joint as soon as you see the molten solder on the side of the joint you've got your iron touching.

Unless I'm using ME weathered rail, I NEVER take a wire brush or scratch brush to the rails, because it's just not necessary unless I'm re-soldering a joint that's been painted.

After having a horrible experience with acid flux eating the ties and forming an ugly white crust on my hand laid code 70 turnouts (Ntrak module) 25 years ago, I don't recommend using an acid flux, unless it's designed to neutralize itself by the heat of soldering the joint.  Common acid fluxes you buy at The Home Depot, Lowes or Radio Shack don't self-neutralize and could be a real problem a year or so down the road.

This works for me, and I've soldered thousands of joints using these products and this technique over the past 20 or more years.  I'm sure there are other products that may work too, but like I said, this works for me.

[ednadolski]

More heat seems to help (ie. applied longer) but the ties are getting melted.

One thing that helps me when soldering handrails is, I cut some tiny strips of paper towel and lay them on the plastic nearest the joint. Then I wet them with a drop of water to act as a heat sink.

For cleaning the metal, sometimes I use a small wire brush in a Dremel.

HTH,
Ed

[peteski]

Hey Bob, the way you are pushing that Super Safe flux, I sure hope that they pay you for your efforts! 

After an earlier lengthy thread about soldering, I did buy some of that flux and just recently I used while soldering leads to SMD 0603 LEDs.  It seems to do the job just as well as my Radio Shack paste flux.  I haven't had the need yet to use it for soldering rail or other larger metal items.

[Dave Schneider]

Thanks for all the suggestions.  I will try my regular iron to see if I can improve things.  I have a decent regular soldering iron, and know how to keep it clean and tinned. The main reason for going the resistance route was for feeders, which seem easier to do if you can grab the wire and rail with the tweezers in one hand. I got overly enamored with the foot pedal and started using it for the joints.

Thanks again, Dave