Soldering is an essential skill for model railroading. We’ve engineered most of our products so that you’ll be able to attach you rails and wires without the need to solder, but as your layout expands, you add bus wires, install command control receivers, etc. you will eventually come across the need. Like using an airbrush or carving scenery, soldering can be an intimidating modeling skill at first but it doesn’t take as long to master as you’d think. Here are three tips every beginner needs to know:
Less is More. You don’t need a big glob of solder to make a good connection. With a little practice and the right tools you’ll be able to get thin, smooth joints that are as strong as the parts you’ve soldered. Use a soldering flux to speed the melting and flow of the solder and you’ll be amazed how much less solder you use!
Solder the Parts not the Iron. It is tempting to put solder on the tip of your iron or gun and then try to spread it on the joint. While a very little bit of solder on the heat source will help the heat transfer, the best joints come from applying the heat to the wire, rails, etc. and then applying the solder directly to the part as well. If possible, apply solder to the opposite side of the joint from the iron. The heat will pull the solder through the gap for a perfect joint. Not only will your solder joints be cleaner and stronger doing it this way, you’ll greatly increase the life of your tools.
A Clean Tool is a Hot Tool. Keep the tips of your irons and guns clean and they will transfer heat better and faster. An easy regular cleaning is to give your hot iron or gun a quick dip in your flux and then swipe on a paper towel. You can also find that over time you lose heat transfer from the tool itself to the tip. Usually, just a loosening and tightening of the screw(s) that hold the tip to the iron or gun will break up any build up in here and you’ll be back to full strength. Of course eventually, the tips do simply wear out and need to be replaced!
Just keep those three basic principles in mind as you work and you’ll be headed in the right direction.
There is of course one more essential thing to keep in mind when soldering no matter what your skill level and that is safety. It should go without saying that a soldering tool gets hot, but it’s an obvious fact that we sometimes forget when we’re crawling beneath a train platform or focused on a project at the workbench.
Keep your tools in a safe place where you are unlikely to knock them over against yourself or other things that might be damaged. This includes plastic models, wood, paper and of course anything flammable. The little stands included with many irons are notoriously unstable. And of course it’s not just the tool but the power cord that can be in the way!
When working under your platform, remember that it’s not only the tools but the hot solder you need to worry about. Gravity as a way of letting you know when you’ve put too much solder on a joint! Avoid working over your head where ever possible. If you must, be sure to wear eye protection. And while parts will cool relatively quickly, they don’t cool instantly. A wire or rail may remain hot enough to burn for a minute or two after soldering. And always unplug your tools when you are finished, even if you are using one with an on/off switch.
If you do get burned, don’t panic. Most soldering burns are painful but relatively small and easy to treat. Cold water is often the fastest and most effective relief. No train room should be without a basic first-aid kit and that should include a cold compress, anti-bacterial cream and bandages for just such an emergency. Equally important is a fire extinguisher – just in case! Of course for more severe burns, seek professional medical attention.
The heat isn’t the only danger with solder. Many solders contain lead. Some fluxes, particular older varieties, also contain some potentially harmful chemicals. Try to avoid inhaling lots of flux fumes and always wash your hands thoroughly after you solder. Store your solder and supplies in places where your kids will not be able to get to it.
Getting Down to Business
Now that we’ve covered the basics, let’s get started on a common project – soldering two pieces of wire. The steps will be described in detail here, but we’ve also included a short demonstration video.
Strip the Wires: Remember that electricity flows around the wire, not through it. So when you strip your wires take care not to nick the wire itself. There are several styles of wire strippers available. Most can be adjusted to the gauge (diameter) of wiring you’re stripping. Strip just enough insulation to make the connection.
- Pre-tinning: It is not always necessary to tin the wires before soldering, but it can make the process go faster – especially if you are working in a small or awkward space like inside a model or under a layout. To tin the wires, spread a little flux on large diameter wire (it probably won’t be necessary on smaller wires), touch it with the tip of your iron or gun, and apply a very thin coat of solder.
- Heat Shrink Tubing: Plan ahead! If you are going to use heat shrink tubing to insulate the finished joint, it is much easier to put the loose tubing over the wires before they are connected. Slide the tube far enough away from the joint that it won’t melt from the heat.
Joining Wires: If you are wrapping a smaller gauge wire around a larger wire – like when attaching feeders to a bus – wrap the wire as tightly as you can. Any gaps between the wires will not transfer electricity. For joining wires end to end, make an “X” and twist the ends together for a tight bond. In either case, only a few twists are needed – the smaller the connection the less solder you’ll need.
- Flux: Apply a little flux to the wires where they need to be soldered. If you have already tinned the wire, this is not necessary.
- Solder: Apply the heat of the gun or iron first. Then touch your solder to the joint. Move the solder and the tool if necessary to melt the solder over the entire joint evenly. A thin coat is all that is required.
Insulate: Once the joint has cooled, you’ll want to insulate the wires to prevent accidental contact and shorts later. You can do this with traditional electrical tape, liquid electrical tape, or plastic heat shrink tubing. To apply the tubing, simply slide it over the joint and warm it with the lower portion (not the tip) of your iron or gun. As the name implies, the heat will shrink the tubing tightly around the wires. You can find this at electronics stores or in bulk from mail-order distributors.
That’s it! You’ve now got a safe, strong and solid connection between two wires. With a little practice, your solder connections will become smooth and reliable every time. You’ll be able to come back to these tips and many more any time on our “Wiring Your Railroad” pages here on the blog.