How To Solder Trackwork

Soldering Trackwork

Application Note

www.fast-tracks.net

Soldering Trackwork in a Fast Tracks Assembly Fixture

The techniques for creating great looking and reliable solder joints aren’t hard to master.

With a bit of practice, anyone can do it. We have shown thousands of modelers how to get

good results with the techniques and tools described in this document.

The instructions we provide here are based on many years of experimenting and experi-

ence. Other materials and techniques may also yield good results, but if you are new to

soldering, then following these instructions as closely as possible will ensure success.

There are four key elements to creating high quality solder joints for trackwork:

1. Keep your tools and works surfaces clean.

2. Use small diameter solder - .020” or smaller.

3. Use an acid based solder paste flux.

4. Use a good quality iron and tip.

We will cover each of these elements in detail in this document. We have also prepared

several soldering demonstration videos that we encourage you to study carefully. Then take

some time and practice on some scrap pieces of rail and PC Board ties before “going live”.

If you do run into problems, check out the troubleshooting section at the end of this docu-

ment for suggestions.

Mechanical vs. Electrical/Electronic Soldering

While the principles of mechanical and electrical soldering are similar, there are important

differences between how mechanical solder joints are created as opposed to soldering

wires and circuit boards. If you are experienced with electrical/electronic soldering, then

you already have the basic skills needed for mechanical soldering.

However, mechanical soldering does use different materials and techniques to create a me-

chanically sound joint. Even though you may be experienced in electrical/electronic solder-

ing, we highly recommend that you study this document and related videos carefully to get

a clear understanding of how to create a mechanically sound solder joint.

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Recommended Soldering Tools

• Micro Applicator Brushes (Fast Tracks part TL-0039 ) — Used to apply small

amounts of flux to the PC Board ties and rail.

• Acid Paste Flux — Kester SP-30 is a good choice.

• . 020” 60/40 Lead Solder (Fast Tracks part SP-0003 ) — Do not try to use lead free

solder. It is not suitable for hand soldering trackwork.

• 35W Soldering Iron With Replaceable Tip — The Weller WP35 is a good choice.

We also suggest a conical shaped tip like the ST-7 tip included with the Weller iron

that we offer on our website.

• Wire Brush (Fast Tracks part TL-0038 ) — Used for cleaning the solder tip and track-

work.

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The Soldering Iron

The best iron for soldering trackwork is a 35W to 45W pencil type iron like the one shown in

the tool image on the previous page. Trigger or gun type irons are not recommended.

There are many ways to economize on the tools that you purchase for building trackwork,

but buying an inexpensive soldering iron is not one of them! The $9.95 discount hardware

store iron will give you nothing but grief.

If you don’t already own one, buy a good quality soldering iron with a replaceable tip. If

you already own a soldering iron, but it is not a good quality pencil type iron, set it aside for

other types of soldering work and invest in a good quality iron for building trackwork. You

should expect to pay between $50.00 and $75.00 for a good iron.

For electronic/electrical soldering

the iron is typically stored in a holder

while it is not being used. We do not

recommend the use of iron holders for

soldering trackwork as we have found

that the tip often comes in contact

with the holder, drawing the heat out

of the tip. As a result, when you pick

up the iron the tip may not be at full

temperature, making it harder to get a

good solder joint.

Image 1

Instead you should set the iron on

your bench top so that the tip is point-

ing upwards. (Image 1) Or find a

stand that positions the tip upward

rather than downward, and does not

have any metal parts that will draw

heat away from the tip. This will help

to keep the tip hot and ready for use.

Be sure to keep an area of your work-

bench clear so that the iron tip does

not touch anything.

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The Soldering Iron Tip

Image 2

For code 100 and smaller track-

work, we recommend that you use

a conical type tip like the one shown

in Image 2. For trackwork that uses

rail larger than code 100, you may

want to consider using a screwdriver

shaped tip. (The Weller solder-

ing irons that we sell comes with a

screwdriver tip. The part number is

ST-3 if you want to order additional

tips.)

Keeping the tip in tip-top shape is

critical to producing sound solder

joints. Inadequate or improper tip

maintenance is one of the leading causes of soldering problems. Fortunately tip problems

are very easy to prevent. Just be sure that the tip is always tinned with a thin coating of

solder at all times!

Most tips are made of a copper core which is electroplated with iron to extend its life. The

non-working end of the tip is plated with nickel for protection against corrosion and then

chrome plated to prevent solder from adhering to it. Only the very end of the tip is un-plated

so that it will accept solder. (Image 2)

The un-plated part of the tip will oxidize very rapidly, so keeping the tip coated with solder at

all times is critical for slowing the oxidation process and extending the life of the tip. Eventu-

ally however, every tip does ‘burn out’. You can tell when this happens as you will no longer

be able to clean the tip so that it is nice and shiny.

When a tip is burned out, it needs to be replaced. Do not attempt to file or sand the tip to try

and extend its life. Instead replace it with a new tip.

To extend the life of the tip and prevent pre-mature burn out, always keep the tip tinned with

a thin coat of solder - not only while you are soldering, but also when the iron is idling. So

before you set your iron down, always apply a coat of solder to the tip.

When you are finished soldering, you should always prepare the tip for storage by cleaning

it and then applying a coating of solder before turning the iron off.

When you install a new tip, the first thing you should do is to apply a thin coating of solder,

otherwise the tip will burn out within minutes.

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Some Comments About Acid Paste Flux

Soldering nickel silver rail to PC Board ties re-

quires that both surfaces are thoroughly clean

and oil free. Acid based flux does a great job

of cleaning the surfaces, and will make it much

easier to produce a nice looking, reliable solder

joint. Especially for modelers who are new to

soldering.

Since we are not building an electronic circuit,

there are no problems with using an acid based

flux for turnout construction. Unlike electronic

circuitry, the solder joints we are creating are

primarily to provide mechanical strength, so the

completed trackwork can be easily scrubbed

cleaned with a wire brush to remove any acid

residue.

The acid used in acid based flux is quite mild, and we have found that as long as the track-

work is thoroughly scrubbed clean with a wire brush you will not have any long term issues.

Additionally, trackwork built with Fast Tracks tools are designed to be painted, which will

seal in any possible remaining acid from oxygen, preventing oxidation and corrosion.

If you are concerned about corrosion over time, then you can also take the additional step

of scrubbing the completed turnout in water with some baking soda. This will neutralize any

remaining acid after cleaning the turnout with a wire brush. However it has been our experi-

ence that this step is really not necessary.

About Solder

Using small diameter (less than .020”) will make it much easier to create quality joints, with-

out the need for excess heat and time. It also makes it easier to access tight spots in the

switch. The solder that we offer on our website ( SP-0003 ) is a rosin core 60/40 solder (60%

tin and 40% lead), however acid core would work just as well. It is just not necessary as the

acid paste flux will take care of cleaning the surfaces.

We only recommend the use of lead solder for hand soldering. The newer lead free solders

require higher soldering temperatures and a lot more skill to get good results. It is also dif-

ficult to tell if you have a good solder joint as lead free solder joints look dull and appear

to be ‘cold’ joints, while in fact they may be just fine. Lead solder is a bit harder to find, but

despite what you may hear, it has not been discontinued and is unlikely to be discontinued

in the future. As long as it is used properly, it is a safe material to use. We will always have

lead solder available on our website.

63/37 solder can also be used. The only important difference is that the melting point of

63/37 is slightly lower (by about 10°) than 60/40 solder.

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Preparing The Ties For Soldering

Image 3

The first step to ensuring a reliable,

good looking joint is being sure that

the surfaces you are soldering togeth-

er are impeccably clean.

To clean the PC Board ties, use a

wide file and lightly file the surface

of the tie until it is shiny and clean.

(Image 3) This is a routine that you

should use for each and every tie that

you solder, as this will ensure both

good solder flow and adhesion.

Nickle silver rail typically does not

tarnish much over time, but be sure to

check the bottom of the rail to be sure

it is also clean and bright. If it has any

tarnish at all, clean it off with a

Brightboy track cleaner.

Image 4

After you have placed the PC Board

Tie and rail into the fixture, apply a

small amount of flux to the rail and tie

interface. (Image 4)

This is best done with a micro ap-

plicator brush. Using these small

brushes will help to ensure that only

the smallest amount of flux is applied.

Using too much flux will result in more

solder being applied than needed

and will make cleanup more difficult.

Be certain to get flux on both the PC

board tie and the base of the rail.

Click The Images For

A Larger View!

If you are viewing this docu-

ment on your computer, and

you have access to the inter-

net, click on any image for a

larger, high resolution ver-

sion.

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Clean the tip Clean the tip Clean the tip!

Keeping your soldering tip clean and shiny will make the difference between success and

failure. Follows is the cleaning routine that we recommend. Get in the habit of repeating this

routine regularly. Certainly whenever the tip looks dull or has any encrusted carbon on it.

Testing The Tip

Apply a small bead of solder to a hot

tip. (Image 5) If the solder balls up

and will not adhere to the tip, go to

the next step, clean the tip and then

try again. Solder will not stick to a

dirty tip or a tip that has carbonized

from sitting while hot.

Image 5

Cleaning The Tip

To begin, first apply a bit of solder to

the tip. If the tip will not take solder,

brush it a bit with a wire brush, and

then try again. After you have coated

the tip with some solder, quickly dip

the tip into the flux. (Image 6) This will

instantly clean and coat the tip. (Im -

age 7)

Image 6

Image 7

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Image 8

Clean any residue from the tip with

a few quick passes of a wire brush.

(Image 8)

When you are finished, the tip should

be clean, bright, shiny, and ready to

solder.

We do not recommend the use of a

wet cleaning sponge typically used

for soldering electronic components.

Cleaning sponges are suitable for

electronics, but tend to cool the tip

down, making it harder to create

sound, mechanical joints for track-

work.

Image 9

The Soldering Process

To start soldering, touch the tip to the

top of a PC Board tie and up against

the base of the rail. The flux will in-

stantly melt and start to sizzle, this is

the best time to start soldering.

Touch the solder to the tip and the top

of the tie to start it melting then work it

into the flux. Where the flux flows, the

solder will follow. (Image 9)

While the solder is still fluid, move the

tip up onto the base of the rail and

hold it in place. (Image 10)

Image 10

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Image 11

While holding the tip on the base of

the rail, apply solder to the opposite

side of the rail. If everything is clean

and properly prepared, there will be

enough heat transfer through the

rail to melt the solder on the oppo-

site side which will draw fluid solder

beneath the rail, creating a very solid

solder joint. (Image 1 1)

Hold the tip of the iron on the rail to

keep the rail hot for a second or two

longer to allow the solder to thor-

oughly liquefy and flow under the rail.

(Image 12)

If you study Image 12 you will notice

that the iron is held at a very oblique

angle - almost parallel to the assem-

bly fixture. Holding the iron at this

angle will help to transmit as much

heat as possible from the tip to the

work surface. Try to avoid holding the

soldering iron at a vertical angle.

Image 12

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Finishing

Image 13

Finally, remove the tip from the rail

while holding the rail steady with a

finger. Keeping the rail in place while

the solder joint ‘freezes’ is critical for

both a reliable solder joint and accu-

rate work. This only takes a second or

two. (Image 13)

The completed solder joint should be

smooth, flat and shiny. Once cleaned

and painted, the solder joints will be

virtually invisible. (Image 14)

Image 14

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Troubleshooting

1. The solder just won’t “take”.

Cause: Surfaces are not clean, or soldering iron not hot enough.

Solution: This problem is almost always caused by dirty surfaces. Be sure that both

surfaces are clean and shiny, and that you have applied a thin coating of flux. Also be

sure that the iron is hot enough and that the flux sizzles and ‘boils’ just before you apply

the solder.

2. The finished joint is dull and grainy-looking.

Cause: The soldered pieces were moved before the solder solidifies, or not enough

heat.

Solution: Be sure you hold the pieces in place until the solder completely solidifies.

Also be sure that you have enough heat so that the solder completely liquefies and

flows between the surfaces.

3. The solder will not melt or flow.

Cause: Soldering iron not hot enough, or dirty tip.

Solution: Be sure the iron is at full temperature and that the tip is cleaned and tinned.

4. The solder joints just look ugly

Cause: Dirty surfaces or tip. Soldering iron not hot enough.

Solution: If the resulting solder joint is not nice and flat and shiny, then the solder did

not properly ‘flow’. To get the solder to flow, you need to be sure that the surfaces are

impeccably clean and shiny, and that the iron is at full temperature before you touch the

solder to the tip of the iron.

5. The copper is coming off the PC Board Ties

Cause: Soldering iron too hot, or left on the surface to long.

Solution: Be sure you are using a 35W to 45W iron and remove the iron from the sur-

face as soon as the solder has ‘flowed’.

6. The solder joint fails (especially on the throwbar)

Cause: The iron was not hot enough, or the solder did not completely liquefy and flow

between the soldered surfaces.

Solution: Be sure the soldering iron is at full temperature and that the solder fully lique-

fies and flows between the soldered surfaces.

7. The soldering iron is not getting hot enough

Cause: Extension cord too long or defective iron.

Solution: You should plug the iron directly into a wall socket. If you need to use an

extension cord, be sure that it is heavy enough for the rated current of the iron and the

length of the cord. (Two wire lamp cords are NOT heavy enough!)

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