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Flex track sections meet on a curve -- ends tend to straighten (= kink at joint). What to do?

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  • Member since
    June 2014
  • From: Ohio
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Posted by josephbw on Thursday, May 13, 2021 8:35 AM

Something that hasn't been mentioned yet, is to let your soldering iron get very hot before you touch it to the rail. That way you can be on and off the joint very quickly.

One trick I do is to wet 2 pieces of paper towel and put them on either side of the joint. When you hear them sizzle you have probably gotten the joint sufficiently hot enough to solder.

As mentioned practice before you do it for real. Also, use the solder sparingly, then there is no to very little cleanup of solder blobs.

Joe

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Posted by York1 on Thursday, May 13, 2021 8:15 AM

Matt,

Someone may have already mentioned this:

It sounds like you have not soldered much yet.  If that's true, before you solder some of your track, try practicing on some scrap ends of track you may have.  Ruin the scrap while you learn so you don't have to use bad words ruining some good pieces of flex track.

York1 John       

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Posted by peahrens on Thursday, May 13, 2021 8:02 AM

A couple of additional points I may have missed above:

1.  It is not essential to have the joints directly across from each other, as both will be part of a rail unit once soldered and each rail will curve nicely.

2.  If ties are close to where you will be soldering and there is concern about tie melting, use heat sinks on the rails next to the joint soldering point.  I used two alligator clips, one on each rail.  That minimizes the heat seen by the next ties.  

Paul

Modeling HO with a transition era UP bent

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Posted by Track fiddler on Thursday, May 13, 2021 7:22 AM

Good morning Matt

Looks like you have some sound advice here about ironing out the kinks on your radiuses by soldering them prior to laying them down.  Has been the solution as long as I can remember here.

Just an FYI for you as I've done several experiments on gluing down track after it's laid with T pins.  Exactly what I'm going to do when I ever get to that point as these experiments were quite successful.

The first experiment I diluted wood glue with water and applied the solution in-between the ties with an eyedropper and let it dry overnight.  It worked very well as the solution seeps under the track ties as the water evaporates as it dries.  The track was adequately secure but could be removed without damaging it with a putty knife.  This works out well if you ever want to change your track routing plan sometime down the road.

As I thought about the interior wood glue solution that is water soluble even after it's dry, it would later get soaked by ballasting.  It occurred to me the track could possibly come loose on the radiuses where there is retention.  I thought of using waterproof exterior wood glue but felt it would become too permanent on the track ties if ever removed.  Once dry, that stuff doesn't like to come off of anything.  I never tried that experiment though because I didn't have any.  It may favor the cork and be the 'Cat's Meow' for all I know.

I did a final experiment with Alex Plus diluted with water and it worked just as well.  Alex is water soluble when wet but becomes waterproof after it is dry.  After it set overnight the track could be removed and the caulk was left stuck to the cork as the track came up clean.  Alex sticks to both surfaces being fastened together but favors the more porous surface to adhere to when pried apart.

 

 

 

TF

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  • From: Dearborn Station
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Posted by richhotrain on Thursday, May 13, 2021 6:21 AM

I have joined as many as 4 pieces of 36" flextrack together and soldered the rail joints on the work bench. If you don't solder the rail joints while the flex track is straight, there is no way to avoid kinks which will cause derailments for sure.

Rich

Alton Junction

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Posted by riogrande5761 on Thursday, May 13, 2021 6:15 AM

mobilman44

In building my last two layouts, I would solder two track sections together (making sure the joints were staggered) and lay out the curve first, and then cut the ends to fit the adjacent tangent trackage.  It worked like a charm. 

I've done the same on my last 3 layouts, except I cut the rails so the joints were even/parallel (not staggered).  It also worked like charm.  I've found no compelling reason to stagger joints.

Rio Grande.  The Action Road  - Focus 1977-1983

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Posted by mobilman44 on Thursday, May 13, 2021 4:56 AM

In building my last two layouts, I would solder two track sections together (making sure the joints were staggered) and lay out the curve first, and then cut the ends to fit the adjacent tangent trackage.  It worked like a charm.

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Thursday, May 13, 2021 2:22 AM

 

Hello,

The advice you found is sound. I soldered all my curved joints while the flex track was straight (tangent) at the area of the joiner, then carefully aligned the remainder of the curve. As you note it is a multi-step process since you have to trim and dress both mating ends of the inside rail.

You'll get the hang of it very quickly.

Flux is a chemical that cleans and aids in the flow of the solder. DO NOT get plumber's acid flux but rosin flux for electronics and wiring. For track work I use Superior #135 paste and apply it with a toothpick. The initial heat from the iron will cause the flux to melt and flow all around the rail joiner, then as the solder melts it will flow and follow the flux.

https://www.amazon.com/SRA-Rosin-Paste-Flux-135/dp/B008ZIV85A/ref=sr_1_2?dchild=1&keywords=solder+flux&qid=1620890646&sr=8-2

There are liquid fluxes and some that are water cleanup and such. It helps to clean off the excess flux after the joint is cool with a cotton swab and soma alcohol.

From Wikipedia:

In soldering of metals, flux serves a threefold purpose: it removes any oxidized metal from the surfaces to be soldered, seals out air thus preventing further oxidation, and by facilitating amalgamation improves wetting characteristics of the liquid solder. Some fluxes are corrosive, so the parts have to be cleaned with a damp sponge or other absorbent material after soldering to prevent damage. Several types of flux are used in electronics.

Good Luck, Ed

 

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Posted by hon30critter on Thursday, May 13, 2021 2:20 AM

Hi Matt,

First, flux is a chemical cleaner that removes metal oxides when heat is applied. It is usually in a paste form but there are liquid forms as well.

The trick to eliminating the kinks is to join the ends of your flex track pieces together before laying them in the curve. Start laying the flex track in the curve, but leave the last 10" to 12" straight. Then solder on the next piece of flex track. Once the rails are soldered you can then lay them in the curve just like it was one continuous piece of flex track.

To solder the rail ends together, join the rails in a straight line with rail joiners. Then apply a small amount of flux to the rail joiner, and then heat the joint and apply solder quickly. If you are quick enough you won't melt the ties. You don't need a lot of solder. There shouldn't be any blobs on the rail joiners or the rails.

One important point is that you must have the right flux! There are two kinds: rosin and acid. Never use acid flux on anything related to model railroading!! The acid continues to eat away at the joint long after the soldering is done, and eventually it will do a lot of damage.

A few other points:

- Most solder for hobby work comes with the rosin already built into the core. However, it is usually beneficial to have some flux separate as well, especially if you are just starting out.

- Smaller diameter solder is easier to control and melts faster. Stay away from solders intended for plumbing.

- Learning to work quickly is the key to avoiding melting the ties. If you prepare the work properly, i.e. everything is clean, the solder should flow into the joint in just a few seconds. As soon as the solder flows into place, remove your iron.

- For soldering rails you need a decent sized iron. It doesn't have to be huge but a 15 watt iron intended for fine electronics won't work.

- You must keep the tip of the iron clean. I use a copper sponge like the ones intended for scrubbing pots and pans (no soap!).

https://www.radioshack.com/collections/solder-and-flux/products/rosin-soldering-paste-flux

Tip cleaning brass sponge:

Dave

I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!

  • Member since
    February 2021
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Flex track sections meet on a curve -- ends tend to straighten (= kink at joint). What to do?
Posted by crossthedog on Thursday, May 13, 2021 1:05 AM

Hi friends,

Cork roadbed is laid for my mainline loop and I'm loosely pinning my turnouts and flex track.

Haven't started nailing the track yet because I need to find a drill bit tiny enough to drill through the ties (Atlas code 83 flex; holes are not drilled all the way through). But I already see an issue. Some of the track segments necessarily meet on the curves, and the last inch of rail does not want to conform to the arc, so I can tell that the joint here will want to have a slight kink.

This effect is amplified by the fact that I had to remove the end tie to be able to fit the rail joiner on, so the rails protrude a little bit, which means there is even less incentive for them to be curved right at the end.

Here's a visual aid.

Obviously I'll be cutting the inside (right) rail a bit to match the other, but you can see how it's taking all these thumbtacks just to force the rails to even PRETEND to curve at the end, and there would still be a kink here if the next section was laid.

I did find this advice online...

To prevent a kink at the joint, join the next section while the joints are straight. Apply a small amount of solder flux to the rails and solder both together at the joint. Using flux and working quickly, you can solder the rail without melting ties.

...but I don't know what flux is, and I cannot envision how this would help.

What are your tricks to maintaining the proper curve through these joints?

Thanks in advance.

-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.

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