12V track soldering

[Brickstepper]

Hello all,

Has anyone got experience in soldering to the 12V electrical tracks? I'm trying to get a good connection for wires, want to solder them to the metal conducting parts. When using flux for inox and 60/40 solder it doesn't seem to flow and bond properly. Would a different type of solder work better there? Also I don't know what kind of material the tracks are, seems like a nickel/steel alloy of some sort, different from normal inox steel.

[legotux]

Hm. I am planning to solder those, if only because I've made a custom 'Frankenstein' 4-point monstrosity where I had to shorten several conductor rails. I have postponed it until now, mostly for fear of the ABS melting and the fumes and damage that come with that. I was thinking how to best conduct heat away by clamping it, but how...  So I can't comment on the process yet.  From your description it isn't clear to me whether you've used plumber solder or electronics solder? If the former, abandon that. I would use electronics solder for sure, as it has flux/resin core inside it. As for soldering, I'd use a bit of sanding paper in preparation, like grain 800 or higher. And remember that with soldering you must always tin both parts before you join them.  If that still proves unsuccessful, which I doubt, you could look into using lead-free solder and its associated flux, since flux for lead-free solder is often more aggressive. But I highly doubt that's necessary.   If I solder them I'll report back my experiences.

good luck!

Legotux 

[Phoxtane]

AFAIK the metal tracks on 9V was nickel silver (nickel, zinc, and copper alloy), not stainless steel. I would assume the same about the 12V tracks. I don't know that you wouldn't be able to solder them with normal leaded solder. I'm a fan of Kester solder myself.

You could borrow a trick from plumbers and HVAC techs where a wet rag is placed on the pipes/refrigerant lines around the joint to prevent the heat from creeping into places it shouldn't be, but you'd need a higher-power soldering iron with a hefty chisel tip to dump the heat in fast enough. Clean the flux afterwards with ispropyl alcohol! (Test the alcohol somewhere hidden on one of the plastic pieces, I'm not sure if it'll react with the ABS or not.)

[legotux]

Hi. I just tried it.  To help cool it, I used a large wrench, that you can see behind it. I did two attempts. Equipment: standard 1mm 60/40 solder with resin core, Weller WTCP-S soldering station.

The one on the right is without sanding, and I needed to rub the iron back and forth a dozen times to make the solder stick, and you can see it is only on a tiny patch still.

The one in the center is after I lightly sanded, and that helped a LOT, it easily tinned and flowed. I was a bit careless with the solder tip, some of the ABS melted because I touched it, but not due to overheating the metal. Getting this result took no more than 2 seconds contact with the soldering iron. Attaching a wire is easy now, and left as an exercise for the reader. (full disclosure: I have been soldering for decades, I'm not exactly a beginner)

@Phoxtane I know the trick but no way I'm letting moisture anywhere near my lego rails, I've seen what it can do to it...

L

Legotux

[Brickstepper]

Great, this really helps. Seems there is quite an oxydation layer on the tracks, even though they are still shiny. The sanding does the trick, the solder bonds well after that. Especially he 12V crossings have issues with conducting as the 4 track pieces are connected by a metal strip that is pressed underneath the rail clamps so was working on soldering those. It has worked, resistance went from 12 Ohm to zero so mission accomplished.
The 12V rails do tend to get rusty when moist so was thinking there must be some iron in there. I used Inox flux but that did not seem to help in getting a good bond to the metal. I used silver solder 3,5% which worked pretty good.

@LEgotux, I would be interested in seeing the points monstrosity you have created, maybe you can post a picture?

[legotux]

1 hour ago, Brickstepper said:

@LEgotux, I would be interested in seeing the points monstrosity you have created, maybe you can post a picture?

Sure, I was planning to do that anyway when finished. But no real harm to post a pic of the thing now.

I'm uncertain this is going to work out well. As you can see this causes both vertical and horizontal offsets in the track. The vertical offset is welcome I think, 12V tracks are normally too close together anyway. But either offset will have to be corrected with the rest of the layout, either by taking advantage of any tolerances there, or by adding other nonstandard tracks/points etc.  Also on my todo list is to add 4 servos to control these. The physical connection details of the moving parts is the hardest part.

Some sections are very dirty, that's on purpose, I selected some of the worst & damaged points I had because I was (and am) unsure if this will become something useful and worthwhile...

A thing I'm not totally happy with is the small wobbly bit that is still there. Perhaps the cuts must be done a bit closer still, but that is a bit more complicated because then the cuts cannot be in line, if I'm making myself clear.

And I'm not yet sure how to strengthen it. It's weak in the middle, and glue won't really work there, because then an adjacent part may break. It needs something else...

 

[Brickstepper]

This looks nice, seems like it saves three whole track pieces in length. I've got some old rundown points lying around but am still reluctant to cut them up... Might have a go at a threeway point though, see if that might work, to save one track in length.
Do you use the Chinese servo's with arduino? I have never used those in combination with Lego.

[legotux]

3 hours ago, Brickstepper said:

This looks nice, seems like it saves three whole track pieces in length. I've got some old rundown points lying around but am still reluctant to cut them up... Might have a go at a threeway point though, see if that might work, to save one track in length.
Do you use the Chinese servo's with arduino? I have never used those in combination with Lego.

Not entirely sure. The (cut-up) track between the ends of the top points measures 18 studs, and a normal track is 16 studs. so there is a 2 stud difference. Normally, to make such a layout requires 8 track lengths, so yeah, it saves (almost) 3 track lengths in the upper section. For the lower section it adds up to two points plus two tracks equals 6 track lengths, so minus two. I think that to be able to reliably add servo's there that track must be irremovable, so the two blue track sections must be indivisible part of the assembly. Alternatively I could shorten these too, but I'm not sure what advantage that would bring me, if any.

But the trains not swaying back and forth (so much) when diverting is an important goal too I think.

I might be able to shave of the last two studs, bringing back the 18-studs track to regular 16, but it's hard and I'm not sure if that's worth it. Obviously, the problem is that now I've increased the distance between tracks from 0 to 4 studs (or from 8 to 12 studs). If I start to move the points two studs closer together horizontally it will also mean that that even 4 studs distance will no longer be true and it'll end up 3.something studs distance, which is very impractical. 

One last possibility I'm contemplating, now that I've started sawing through rails, is to add a fifth point, where the 18-stud section is now, shortening the rails as required. That way you get a two-to-three track thing. But I'm not sure that is a good idea.

Yeah I went and bought a set of 11 damaged points off ebay for €25 so I can experiment without fear. The servos I plan to use are regular, non-Lego $2 servos which I plan to control with an arduino. Not to automate them, just to interface between a pushbutton switch and the points. Lots of things to still figure out, like suitable connectors, etc. So, no Lego parts involved there.

Legotux