soldering unitrack for reliability?

[nik_n_dad]

Hello.

 

We have a few spots on our layout where we get some stalls, including a span of bridges.  It's feeling like we have some less-than-great connections on spots with the unijoiners (especially in the spans of bridges).

 

What are your thoughts about soldering a number of joints?  Are there issues? Concerns? Warnings? Experiences?

 

TIA

[kvp]

You should measure the voltage first. If there is no drop, then it might only be dirty track. Soldering the tracks can lead to problems with termal expansion of the tracks, like in the prototype. Adding a few extra power feed points to these areas is imho better. Unless there is stress in the tracks, which means the unijoiners are not fully connected, there should be no serious problems. If you connect and disconnect modules a lot, then you might need to replace the joiners there.

[Bernard]

Good question: I use flex track and have to solder the joins but for the Kato bridges I have on my layout which has unitrack, I don't solder those joins.....I found that the unijoiners are very tight.....is it possible that some of the unijoiners might be bent?

KVP makes a good point to check the drop in voltage.

[cteno4]

Yeah always check the unijoiners. Best to just have a couple of packs to spare and if one gives any issues just replace it. I use to fiddle with them with micro pliers to fix most, but now find it just simpler and probably longer lasting to just replace them. That little odd plastic bit that comes with the retailers is actually a cleanse gauge and a unijoiner puller. Just slip it over the end of the unijoiner in the large slot and slide it down to the skinnier slot and then you will have a nice tab to pull the unijoiner out.

 

Jeff

[nik_n_dad]

Thanks for the replies.

 

In many cases, the track is glued-down as this is a permanent layout, so swapping out unijoiners isn't an option.

 

Regarding the span of bridges, we have a series of bridges and viaducts that cut across the layout and in a few spots are small regular-style pieces of curved track (those are supported by foam scenicking).  With the span being about 5' with the only support being the kato unitrack piers, there's quite a bit of play in the track and joiners, hence my thought about soldering a couple of the sections together to provide better support.

 

 

[kvp]

In this case (a bridge with large movement), i would rather add more feeders, even if it means running bus wires under the tracks. Soldering together something that supposed to move means the dynamic load of the bridge would be on the solder joints and that could be really bad. Not to mention soldering together large stretches could lead to tracks being pulled apart when the temperature get colder or buckling in hotter weather (just like with real continously welded rail). Adding feeders to both ends of a bridge and keeping it sectional might be a better and easier option. Just check what is the problem first. For lattice girder bridges, the stalling is usually caused by not being able to clean them properly though the girders. So try to isolate the problem first.

 

ps: If you want stiffer bridges, then you might be better off with replacing the unijoiners first with new ones, then gluing or swrewing together the bridge frame sections. This way the rails won't have to hold the load of the bridge but the frames will be much stiffer. Just be careful, because this could also lead to stress cracks if the dynamic load is really that high. (usually it's caused by having a bridge on or near a curve, on a gradient or on top of really high piers)

[Bernard]

One problem with soldering unijoiners is the plastic that surrounds the joiner.....you have to be very careful not to melt the plastic. I did solder some Unitrack and as I recall it wasn't easy, I think there is a coating on the rails that you'll have to file away.

[cteno4]

One thing to try before you head to tearing up track or soldering in place would be to try a little spray contact cleaner and a tiny contact cleaner (wire or fiberglass) to try to clean a joint. Local electronics store will have small cans of it or go online. Make sure to get one that is plastic safe and test it first on a spare piece of track first. Contact cleaner is meant to help clean out gunk in electrical contact situations just like unijoiners and track

 

Jeff

[KenS]

Unijoiners (and any other style of sectional track joiner) can become less tight over time if the track is assembled and disassembled repeatedly.  A good test for this is to use a multimeter to measure resistance between two connected sections of track (be sure to unplug/unscrew the far end of any feeders).  A bad unijoiner will show resistance that's fairly high, >3-5 ohms, often tens of ohms.  A good one may show a few ohms of resistance (1-3).  You aren't likely to get visible problems until resistance is tens of ohms, although this varies a lot  (V = IR says a 100 mA current on a 10 ohm resistor causes a 1 volt drop; a single loco is likely under 50 mA, a lit train could be over 200 mA). I try to replace any unijoiners showing >5 ohms of resistance.

 

Sometimes it's the track not the unijoiner that's bent. So if you replace a 5 ohm unijoiner and it doesn't change the resistance, you either need to live with it, or replace one or both track elements.

 

Dirt will cause similar problems in track that stays out and exposed to dust over the long term (or if you've been doing scenery work nearby).

 

The hard part is that if the track is built in place, it's going to be impossible to swap the unijoiners.  Although I haven't done it myself (my track can be disassembled for maintenance, although it's a pain to do), if I were building permanent bridges with sectional track, I'd solder a jumper wire to the underside of the rail maybe an inch or two back from the joiner on each side, to carry current past the unijoiner.

 

There was a thread a while ago about how to solder to the underside of track.  I can't seem to find it now, but that advice could be adapted for a bridge. The key point is to clean and pre-tin both wire and track, and if possible I'd also use a solder heat-sink clamp (or haemostat) on the track to keep heat away from plastic ties. Pre-tinned, very little time should be required to solder the wire, and the track won't heat enough to damage ties.  It is something you should practice on scrap track first though.

 

Since the underside of the track on a bridge is visible, making the wire small is important.  Magnet wire of an appropriate size could be used since its insulation is painted on, and thus very thin. And if you can glue the wire to the bridge underside and paint it, it may look something like a drain pipe or prototype electrical conduit even if it is visible.

 

If you have feeders at both ends of the bridge, so you know current draw on the bridge will be only a single train per track, very fine wire could be used for this: 30 gauge magnet wire should carry up to ~400 mA before it becomes hot enough to be a problem with styrene (75C). And 30ga (0.05 square mm) wire is often used for short wires to decoders that need to handle up to 1 Amp so that number probably is on the conservative side. However, I've seen contradictory information, and might be inclined to use 28ga (0.08 square mm) just for a safety margin.

 

Note: long small wire becomes problematic due to resistive voltage loss, which is why we don't use 30ga for track feeders. But a short jumper between adjacent track sections is more like a decoder lead than it is like a feeder.

[cteno4]

Ken,

 

good thoughts, i was thinking along the same way of suggesting jumpers like this to get past bad fixed joints. could be done on the side of the track and hidden. since its along the track could even just use solid wire w/o insulation like lead wire (i think thats what its called, solid core stuff like small used in small electronic component contacts). even see some wire jumpers like this on the prototypes.

 

to solder to the underside of tracks you just need to cut a slot thru the roadbed under the track. two ways ive done this are using a roto tool to either use a V router tip to hack out a 1/2" or so slot or use a mini circular saw on a roto tool to do the same. Ive done it both ways and both work. it does take a bit of practice to get good so take an old hunk of track and sacrifice it to practice and find what works for you. I then just tin the wire and tin the underside of the track and then put the two together and quickly fuse with the soldering iron. probably would need to cut some slots in the ends of the track to find a place for the wires to travel thru the joined ends.

 

ive often wondered how much extra resistance some dielectric grease would add to a unijoiner joint to try and keep dirt and glue and such out of unijointers that are nailed down. in theory in a pressure connection the grease is squeezed out of the metal to metal area and just surrounds the joint to protect it. conductive greases dont sound like they would add anything maybe in this situation. something to experiment with at some point.

 

cheers,

 

jeff

[nik_n_dad]

Although this topic it old, we managed to fix the problem with a thorough cleaning.  Although we had cleaned the track and cleaned the track, apparently it wasn't enough from a few years of sitting in the garage (layout has been moved into the basement and is sorta up and running).

 

What ended up working for a good cleaning was the "RailTracker Cleaning Kit" by Woodland scenics

http://woodlandscenics.woodlandscenics.com/show/Item/TT4550/page/1

Going through theit step-by-step process and using all their different "attachments" has given us pretty-clean track and good running.

[inobu]

NND,

 

I think. KVP  touched on your problem. You are running DCC so voltage drops are not as prevalent because the dc voltage is created by the decoder.

 

Unitrack has it pros. The cons are the connections.

 

There may be a load issue but it may very well be the load that the train puts on the track. The weight of the train can cause the track to move. This movement can cause a loss of continuity into the joiner.  

 

Even the off camber of the track can create problems. Although we cannot see the twist in the track the motor car can.

 

The tolerance is so minute that tapping the table can get the train going again.

There are a few things that you can do to troubleshoot your problem.

 

enter the area from both direction. If you can pass through the problem area in one direction and not the other then it would be safe to say its a joiner. That proves that voltage is in that area.

 

Observe the track movement if any as the train passes.

 

Inobu

 

Note: when you are laying the track down, on the final placement crimp the joiner a little and make sure not the pull

The track apart.