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

[riogrande5761]

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.

[Overmod]

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.  

[richhotrain]

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

[richhotrain]

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

[Water Level Route]

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.

[dstarr]

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. 

 

[doctorwayne]

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

[crossthedog]

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