Trains.com

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

First attempts at soldering joints in flex track -- naturally, questions arise

7296 views
44 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    February 2021
  • 1,110 posts
First attempts at soldering joints in flex track -- naturally, questions arise
Posted by crossthedog on Thursday, May 20, 2021 10:33 PM

I did a few practice runs on some old rail that my dad had left (brass, Code 100), since I don't have any "spare" track yet. Everything else I have is new Code 83 flex track. The third attempt was messy but seemed to be solid, so I took a deep breath and tried a joint on two pieces of my new flex track. I'm not sure it looks like it should. Below you can see the outside of one rail and the inside of the other.

On both rails, I put the soldering tip on the top or the outside, not on the inside. I didn't do anything on the inside of the rails except put (rosin core) flux paste there. I hoped the solder would flow to the insides. Hard to tell whether it worked. However, before I pushed the rail ends together I actually put a dab of flux right inside the rail joiner. I think the outside top/right one looks okay, but a dab of solder got onto the top of the rail there, and on the lower/left rail the top got quite a bit of solder on it. I'm just clumsy.

Questions:

In your view will these soldering jobs hold on a curve, or do I need to redo?

How should I get the solder off the top of the rails? should I file it? Sand it? What do you do (besides not get solder on the top of your rails)?

Where do you guys actually touch the soldering iron to the rail to heat it up? On top? On the outside?

My next questions are about the strategy for where joints go around my curves. In the picture below, I've marked with a red pin where one three-foot section of flex track will end. It's not quite out of the curve. There's a short straight section there that you can see better in the last photo (to avoid an S curve) but that track won't reach the straight. 

The green pin shows where the next one ends, a frustrating cubit shy of the turnout. All bad luck. I had rathered a single long piece would come all the way to the turnout and connect to it on that straight. However, I'm starting at a turnout on the other side of that long curve by the wall, so if I move everything forward to this turnout I'd just have the same issue at the other end. 

Question:

Would it be smart to shorten one of the pieces by the wall so that the track now ending at the red pin would end sooner? I would have the same number of joints on the curve, but I could then engineer a longer piece that would come onto the straight between the red and green pins (I think a short piece with a curved end would be trouble), and the last piece could reach onto the straight before the turnout.

Or... what... ? I guess I'm asking, where and how would you guys put the short pieces that I'm going to have to use to fill in to reach the turnout?

Here's the other view of the area between those pins. You can see the very small straight part.

I haven't heard anybody say, "geez, just man up and figure it out!" yet, so I'm going to keep asking questions until someone does. I'm trying to ask specific questions and supply clear photos.

You guys will be able to consider this a community railroad if it works out, because all of you will have ended up providing input without which this wouldn't be happening.

Humbly grateful for all input.

-Matt

 

 

 

 

 

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    January 2004
  • From: Canada, eh?
  • 13,375 posts
Posted by doctorwayne on Friday, May 21, 2021 1:16 AM

I wouldn't worry about where one length of rail ends - figure out roughly how far you need to go before you come to a turnout (or the end of a siding), then solder together enough lengths of flex track to get there.

If you overshoot it a bit, cut off the excess, add the turnout, then carry on in the same manner.
This will allow you to do the soldering as a straight length of track, which can then be curved, as required, to follow the cork roadbed that you already have in place.

You can use a not-too-coarse file to clean the solder off the top of the track - leaving it in place is a derailment waiting to happen. 

As you continue to add and solder subsequent lengths of track, your confidence will grow, as will your abilities.  It's good to be cautious, but don't let it make you timid...you've already made some solder joints, simply carry on - you can do it!

Wayne

  • Member since
    August 2006
  • From: Franconia, NH
  • 3,130 posts
Posted by dstarr on Friday, May 21, 2021 1:47 AM

Your solder joints look OK.  The solder is shiny, the mark of a good joint.  Joints that have a frosty look to them are called cold solder joints and should be reheated with the soldering iron and allowed to cool without moving them. 

   I get unwanted blobs of solder off with a small file. 

   I use a big iron or a soldering gun good for 100 watts or more.  I keep the tip clean and shiny (tinned).  That black crud that builds up is an insulator and will slow the flow of heat to the joint.  I press the iron right on the rail jointer.  We want solder to flow by capillary action all down the inside of the rail joiner.  This works best if the rail joiner is good and hot.  I use a couple of alligator clips as heat sinks on either side of the joint to cut down on the melting of ties.  I use 60-40 tin lead solder.  Avoid the 50-50 solder, that is only for plumbing. I use rosin flux. 

 

  • Member since
    February 2015
  • From: Ludington, MI
  • 1,862 posts
Posted by Water Level Route on Friday, May 21, 2021 5:48 AM

crossthedog
In your view will these soldering jobs hold on a curve, or do I need to redo?

Always hard to tell by a photo, but your joint does look fine.  Give it a gentle tug.  If you can't pull the joint apart, it should hold just fine.

crossthedog
How should I get the solder off the top of the rails? should I file it?

Yup.

crossthedog
Where do you guys actually touch the soldering iron to the rail to heat it up? On top? On the outside?

On a side (inside or outside), but never on top.

crossthedog
Would it be smart to shorten one of the pieces by the wall

Not necessary.  Joints in curves is a reality of layout construction and done properly (you are well on your way to that) won't be a problem.

crossthedog
where and how would you guys put the short pieces that I'm going to have to use to fill in to reach the turnout

As the last piece laid down.  Trying to guess what length filler piece you need, and then putting it in the middle of the run opens you up to having to cut the length down again because you misjudged and made your filler too long, or worse, too short and have to work in more.  Just work from one fixed point to the next (turnout to turnout for example) and cut you last piece to fit.

You're doing fine.

Mike

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Friday, May 21, 2021 6:22 AM

Your soldering job looks sufficient to me, but I always make sure that the solder covers the entire entire rail joiner. I can see the ends of the rail joiners in your photo.

There is no need for solder to enter the inside of the rail, and you want to avoid that as it could interfere with wheel movement.

As far as the blob of solder on top of the rail, place the hot tip of the soldering iron to melt it and rub off the melted solder with a rag. Gotta act quickly before the solder cools.

Rich

Alton Junction

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Friday, May 21, 2021 6:31 AM

crossthedog

My next questions are about the strategy for where joints go around my curves. In the picture below, I've marked with a red pin where one three-foot section of flex track will end. It's not quite out of the curve. There's a short straight section there that you can see better in the last photo (to avoid an S curve) but that track won't reach the straight. 

The green pin shows where the next one ends, a frustrating cubit shy of the turnout. All bad luck. I had rathered a single long piece would come all the way to the turnout and connect to it on that straight. However, I'm starting at a turnout on the other side of that long curve by the wall, so if I move everything forward to this turnout I'd just have the same issue at the other end. 

Question:

Would it be smart to shorten one of the pieces by the wall so that the track now ending at the red pin would end sooner? I would have the same number of joints on the curve, but I could then engineer a longer piece that would come onto the straight between the red and green pins (I think a short piece with a curved end would be trouble), and the last piece could reach onto the straight before the turnout.

You are worrying unnecessarily about short sections of track. Once the entire length of flextrack is soldered between sections, it becomes one long section of flextrack that you can bend without kinks to the desired shape. I don't see any problems in those 2nd and 3rd photos.

Rich

Alton Junction

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Friday, May 21, 2021 6:39 AM

In general, when soldering (by whatever method of heating) the substrate -- here, the two rails and the joiner -- are heated enough to melt the solder and flux that are applied.  The liquid solder will then run into the joint with capillary action.  The indirect heating from the iron is continued until that has happened.

I advise applying the iron to the outside of the joint (and incorporate any feeder wires there).  That is because the gauge corner and flange face of the rail are important to running, and you want to minimize buildup and blobbing there.  You can build up about as much metal as you can stand on the outside faces of the rail and it won't affect running...

Some solder is made to be 'sludgy' for a time while it is hardening.  That's an advantage in some applications, but not here: if you move the joint, or let it move or 'spring' even a little, you'll get that frosted appearance that says the joint isn't as strong.  There are compositions of solder ( for example in the 63:37 range) that harden nearly at once.  Those have the fancy name "eutectics".  I advise you use them for this kind of work.

As a general rule: don't apply the iron, and don't apply the flux, to any surface you don't want solder to adhere to.  You can reheat the joint area (from the outside) and use a piece of solder braid to 'wick up' any solder that's gotten where it shouldn't be.

You file the rails, not sand them, for a simple reason: you want the finished railhead and gauge corner to be clean and flat.  Unless what you use is very flat and rigid, you'll tend to get a bump at the solder blob.  

  • Member since
    June 2007
  • 8,892 posts
Posted by riogrande5761 on Friday, May 21, 2021 7:22 AM

The solder joint looks good to me. I've never been great at soldering so I clip heat sinks on before soldering.  That way if it takes a little longer to heat and appy the solder, the ties won't melt.

Your track work looks nice and flowing so far.

Rio Grande.  The Action Road  - Focus 1977-1983

  • Member since
    December 2008
  • From: Heart of Georgia
  • 5,406 posts
Posted by Doughless on Friday, May 21, 2021 7:39 AM

As others have said, everything looks fine.  Ugly soldering joints are okay of they are on the outside and facing the backdrop.  You wont see them.

For the track that faces the benchwork edge, I solder on the inside of the rail.  I would not want to get a lot of solder in the joint where a wheel might hit it.

Always placing the tip on the inside or outside of the rail, never on top.

If you get too much solder in the joint where you don't like the appearance, I shmear flux over the blob and the bare side of the rail.  Applying heat to the solder with the flux tends to melt and thin the solder so it flows throughout the joint.

For really heavy or unsightly solder blobs, you can heat up the solder the same way and wipe off with a wet paper towel.  The towel needs to be quick, almost touching the iron tip as you remove the iron and follow quickly with the wet towel.

- Douglas

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Friday, May 21, 2021 7:42 AM

Doughless

For the track that faces the benchwork edge, I solder on the inside of the rail.  

Say what? You are a brave man, Douglas. I would never solder on the inside of the rail.

Rich

Alton Junction

  • Member since
    June 2007
  • 8,892 posts
Posted by riogrande5761 on Friday, May 21, 2021 7:59 AM

richhotrain
 
Doughless

For the track that faces the benchwork edge, I solder on the inside of the rail.  

  

Say what? You are a brave man, Douglas. I would never solder on the inside of the rail.

Rich 

Same here.  I'd rather not risk any solder interfering with the flanges.  You can solder on the out side of both rails and it will be fine.  As long as there isn't a ton of solder, after you paint the track, it shouldn't be a detraction from the appearance.

Rio Grande.  The Action Road  - Focus 1977-1983

  • Member since
    February 2015
  • From: Ludington, MI
  • 1,862 posts
Posted by Water Level Route on Friday, May 21, 2021 8:09 AM

riogrande5761

 

 
richhotrain
 
Doughless

For the track that faces the benchwork edge, I solder on the inside of the rail.  

  

Say what? You are a brave man, Douglas. I would never solder on the inside of the rail.

Rich 

 

 

Same here.  I'd rather not risk any solder interfering with the flanges.  You can solder on the out side of both rails and it will be fine.  As long as there isn't a ton of solder, after you paint the track, it shouldn't be a detraction from the appearance.

 

I've done this, but only when/where I've had to due to not being able to see what I'm doing on the outside of the joint.  One has to be VERY careful doing this though.

Mike

  • Member since
    July 2006
  • From: west coast
  • 7,667 posts
Posted by rrebell on Friday, May 21, 2021 8:53 AM

You want to make it pretty, just get the iron up to temp and swipe it over all offending soulder. I tend to end a joint by running the iron over the head real quick to smooth out any stray soulder and thin it out if it exists, make any touchup filing effortless. Even major messups can be fixed, once had a joint on a curve that was done after it was laid as the whole curve setup was too long to do in one piece, it looked like it was kinked but it wasn't as I  filled in and filed the offending kink and filed away the kink on the other side, a lot of work but it ran perfectly but would find another way if I had that situation again but a good example of you can fix it.

  • Member since
    May 2004
  • 7,500 posts
Posted by 7j43k on Friday, May 21, 2021 9:27 AM

Me too!

That is:  I agree that your solder joints are good.  You want a nice smooth good-looking flow.

 

But let's talk about ties:

 

You might heat damage a tie.  This is NOT a problem.  Cut it off with your rail nippers.  

Whatever you do, you'll likely have a tie-less section.  One option is to insert single replacement ties underneath.  You'll probably have to clip off the "spikes", but you might get lucky and snap them on.

For the rail joint section, you do NOT want to do this, as it will raise the rail at this point, since there's the additional thickness of the rail joiner.  You might file those replacement ties thinner, but I cut my ties into pieces, removing the section at the rail joint.  Then I just drop them down from above.  You can't see under the rail joiner, so the missing section isn't a problem.

 

The big thing is to not have a bump caused by you replacing the missing ties.

 

Ed

  • Member since
    December 2008
  • From: Heart of Georgia
  • 5,406 posts
Posted by Doughless on Friday, May 21, 2021 1:48 PM

richhotrain

 

 
Doughless

For the track that faces the benchwork edge, I solder on the inside of the rail.  

 

 

Say what? You are a brave man, Douglas. I would never solder on the inside of the rail.

 

Rich

 

Yes, I've always soldered on the side of both rails that face the backdrop.  Done probably over 100 joints over the years.

If you use enough flux and not too much solder, the solder flows into the cracks and doesn't leave any blobs.  Make the rail nice and hot before applying the solder to the (GERN) fluxed joint.

BTW, if you use GERN Flux, it will be a solid joint!

- Douglas

  • Member since
    December 2008
  • From: Heart of Georgia
  • 5,406 posts
Posted by Doughless on Friday, May 21, 2021 1:53 PM

Lastspikemike
The number one mistake in soldering is using too much solder. That's what causes the bumps and lumps you need to grind off with a fine needle flat file or a Peco track cleaning block. The soldering iron isn't used to apply the solder, it heats the joint so the solder melts when applied to the joint. If you avoid touching the soldering iron with the solder

Ditto.  And slide the tip over the joiner back and forth to smooth out the work.  If the solder sticks to the tip as you raise it, there is way too much solder on the joint.

And the proper way to do it, would be to heat the opposite side of the rail from where you apply the solder, to draw the solder through the joint.

But I've found that heats up the rail very hot and it tends to melt the ties that are even half an inch away.

Its not a plumbing joint where we need to avoid voids and leaks. We're just securing some rail joiners.

- Douglas

  • Member since
    February 2021
  • 1,110 posts
Posted by crossthedog on Friday, May 21, 2021 5:32 PM

Guys, thanks so much for all this. Good to know I haven't completely flubbed the job, and there's lots of good sound counsel here. I feel a lot less intimidated having done one joint.

Lastspikemike
So, you cut and lay the final pieces of flex track to the required length to connect up your turnouts already in place. Your final joints will also be easier to fit if they are within a curve.

Mike, I think you mean exactly the opposite, right? That the final joints will be easier if they are NOT within a curve, or? At the end of the day, though, there will be joints in curves. I'm taking the advice to solder together several flex-track lengths to reach from one fixed point to the next, and only cut down one piece.

Doughless
GERN flux

Douglas, what is GERN flux and why do you like it? I have two tins of rosin flux already, one of Kester 135 Rosin Core that I ordered online and another of Weller rosin core that came with the soldering iron cleaning and tinning kit. I was originally hoping to get liquid no-clean, but I find that the paste is very nice in that it starts to sizzle and go opaque when it gets hot enough to solder. I like tools that talk to me. Smile

-Matt

 

 

 

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Friday, May 21, 2021 5:40 PM

crossthedog

At the end of the day, though, there will be joints in curves. I'm taking the advice to solder together several flex-track lengths to reach from one fixed point to the next, and only cut down one piece.

And you will not regret that decision for one moment.  Yes

Rich

Alton Junction

  • Member since
    December 2015
  • From: Shenandoah Valley
  • 9,094 posts
Posted by BigDaddy on Friday, May 21, 2021 5:45 PM

crossthedog
Douglas, what is GERN flux and why do you like it?

GERN Flux Big Smile is an imaginary product invented by our own DrWayne, with a following of religious proportions and will be of no use at all for your purposes.

Henry

COB Potomac & Northern

Shenandoah Valley

  • Member since
    January 2004
  • From: Canada, eh?
  • 13,375 posts
Posted by doctorwayne on Friday, May 21, 2021 7:16 PM

BigDaddy
GERN Flux Big Smile is an imaginary product invented by our own DrWayne, with a following of religious proportions and will be of no use at all for your purposes.

Actually, GERN is my brother's creation, and while it has nothing to do with soldering, GERN-brand flux makes everything at least 3% better.

If the image is too small to read, simply click on it for an enlarged version.

Wayne

  • Member since
    May 2004
  • 7,500 posts
Posted by 7j43k on Friday, May 21, 2021 8:01 PM

In my experience, it's much better to lay the switches first, the curves next, and fill in finally with straight.

It is VERY easy to fit afinal straight "fitter" piece--you just cut it so that each rail is the same length as the two gaps you need to fill.  NO guessing.  Just cut it and drop it in.

If you're working in the curve, you're going to have to fiddle around to get your lengths right, and keep doing test fitting until you (hopefully) do.

Install your switches.  Build your curves.  Connect them all with straight, and drop in the last "filler" pieces.

 

 

Ed

  • Member since
    December 2008
  • From: Heart of Georgia
  • 5,406 posts
Posted by Doughless on Saturday, May 22, 2021 7:35 AM

LaughLaughLaugh

I've always loved inside jokes.

Thanks Wayne, for cleaning up my potential mess.

- Douglas

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Saturday, May 22, 2021 8:48 AM

Wayne, post the one about how to identify fake foreign flux.

  • Member since
    February 2021
  • 1,110 posts
Posted by crossthedog on Saturday, May 22, 2021 9:41 AM

Very funny, gentelmen. ("A wise guy, eh?")

I went looking for GERN flux online but I kept running into websites trying to sell me a turbo encabulator.

Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.

  • Member since
    September 2003
  • 21,669 posts
Posted by Overmod on Saturday, May 22, 2021 10:43 AM

Ah, the turboencabulator (please note that it's one word, despite what you might read 'elsewhere').

As happens, I was briefed on the pre-Quick version of the thing; it is of course difficult to know for sure where the doubletalk name came from but it's difficult to imagine it spontaneously evolved at the same time on both sides of the Atlantic.  The Chrysler parody and its sequels both apt and inapt have further expanded and polished Quick's 'canon' -- although I still don't understand how the obvious misspelling of 'wainshaft' has never been corrected -- but the original was a Naval project involving a critical aspect of battle communications.

In the old days of radio, so-called 'static' was a problem with clear reception.  A team at ONR determined that this was due to 'bad electrons' and that if some way to filter these out of RF current could be devised, the problem could be reduced or eliminated.  The result was the original turboencabulator, which used resonant... i don't remember the correct doubletalk word... to separate the bad electrons and charge a large capacitor with them; this would then be disconnected and fired out of one of the ship's eight-inch guns, allowing clear radio communication.

Of course, the bad electrons would discharge upon contact with ocean water, and find their way back to the metallic hull.  But this, ONR pointed out, was a function of the drift speed of bad electrons, much slower than near-lightspeed, so there would indeed be a clear period where the method would work.

Apparently this was officially sanctioned as a test to see how many levels of Naval oversight this would pass through before someone threw it down on his desk and, after he stopped laughing, put the kibosh on it.  I heard it got a surprisingly long way... although some of that was probably an understanding of the in-joke involved. 

  • Member since
    January 2004
  • From: Canada, eh?
  • 13,375 posts
Posted by doctorwayne on Saturday, May 22, 2021 10:58 AM

Overmod

Wayne, post the one about how to identify fake foreign flux.

 
Yes, it's a real "buyer beware!".  If the small print is difficult to read, simply click on the photo for a larger view.
 
Wayne
  • Member since
    November 2002
  • From: US
  • 2,455 posts
Posted by wp8thsub on Saturday, May 22, 2021 11:43 AM

richhotrain
 
Doughless

For the track that faces the benchwork edge, I solder on the inside of the rail.  

 

Say what? You are a brave man, Douglas. I would never solder on the inside of the rail. 

 

It's interesting to see how many avoid soldering on the gauge side of the rail.  I do it all the time, and there's never a concern with excess solder buildup.  If you use the right amount of solder, and heat the joint properly, this just isn't a problem. 

I place the iron where it's easiest to reach.  Since I like to heat one side of the rail while applying solder to the opposite side, it's easier for me to hold the iron on the back side of the rail.  About half the solder joints on my trackwork were probably done with the iron on the inside of the rail.

Rob Spangler

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Saturday, May 22, 2021 2:30 PM

wp8thsub

It's interesting to see how many avoid soldering on the gauge side of the rail.  I do it all the time, and there's never a concern with excess solder buildup.  If you use the right amount of solder, and heat the joint properly, this just isn't a problem. 

That's two big IFs, and therein may lie the problem.

Rich

Alton Junction

  • Member since
    February 2015
  • From: Ludington, MI
  • 1,862 posts
Posted by Water Level Route on Saturday, May 22, 2021 2:59 PM

7j43k

In my experience, it's much better to lay the switches first, the curves next, and fill in finally with straight.

It is VERY easy to fit afinal straight "fitter" piece--you just cut it so that each rail is the same length as the two gaps you need to fill.  NO guessing.  Just cut it and drop it in.

If you're working in the curve, you're going to have to fiddle around to get your lengths right, and keep doing test fitting until you (hopefully) do.

Install your switches.  Build your curves.  Connect them all with straight, and drop in the last "filler" pieces.

 

 

Ed

 

I agree completely.  

Mike

  • Member since
    September 2004
  • From: Dearborn Station
  • 24,281 posts
Posted by richhotrain on Sunday, May 23, 2021 6:54 AM

7j43k

In my experience, it's much better to lay the switches first, the curves next, and fill in finally with straight.

More power to those who can lay track in that sequence.

When I start a "curve", and I am speaking of at least a 90 degree curve (a quarter circle, if you will), I begin one end of the curve by connecting it to the last section of straight track previously laid.

Then, I form the curve, including easements, and then I connect the completed curve to the first section of straight track adjacent to the end of the curve.

If that first section of straight track adjacent to the end of the curve is a turnout, I obviously know at that point exactly where to place it. How could I know that beforehand?

Rich

Alton Junction

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Users Online

There are no community member online

Search the Community

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!