# How an LGB switch can go bad



## JackM (Jul 29, 2008)

To me, the cramped and convoluted tracks in a train yard are pure art. So I'm a sucker for complicated track work in the model world. If I could figure out ways to use more double-slip switches, I sure would. Unfortunately I could only justify one of those works of art in the yard I built last summer. And, as luck would have it, I happend to snare a used LGB double-slip on eBay for a mere fifty bucks! (Admittedly it's got awfully tight curves, but I was a bit short on space anyway, and the price was right.)

All was well with the installation - ignoring the fact that the LGB switch is brass and ALL the rest of my track is stainless. I don't care; it works. But after a few months of flawlessness, strange electronic things started happening. The power supply needed to be reset periodically but I was never sure of the reason. Then the yard switch engine started acting strangely, then unceremoniously blew its decoder board.

I was stumped until one day I was topping up the ballast near the double slip while a small train circled lazily around the flower beds. I happened to put a hand down on the double slip and found it was pretty HOT! Not the entire switch, but a couple of the rails. Eventually I figured out that the rails got hot only when the points were set in a particular formation. As long as I didn't set it to the stub lead track, the switch was at normal temperature. But as soon as I threw it to feed the stub, things got hot.

I gradually pieced together the puzzle and just didn't use the stub for the rest of the season, then brought the switch into the house for the winter. Here's what I found when I removed the screws that held on the two pieces of overheated plastic:










The plastic pieces (arrows), each held on with two screws, have obviously been well heated. The strips of metal (circled) that connected the appropriate rails above were bent so that they were almost touching. I'd guess that the weight of rolling stock caused the strips to get a few sparks flying. A simple push on the inner strip got it back to its presumed original spacing, a good 1/4 inch from the other strip.










I have no idea whether all this happened only since I got the switch, or if the eBay seller knew of the problem. Doesn't really matter at this point. The design doesn't seem faulty; I would expect the strips to maintain their positions, so this should never have happened. To make sure it doesn't happen again, I sqooshed (technical term) some RTV sealant between the strips, so now there's a rubbery blob keeping these guys apart.

Go figure.

JackM


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## Greg Elmassian (Jan 3, 2008)

Could have been the ballast pushing them together. 

Fiill the undersides of any switch with silicon rubber where there are connections/bare wires. 

Greg


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## chuck n (Jan 2, 2008)

Over the 30+ years I have been in the hobby, I have had to replace a few connectors on switches. Electrolysis results from dissimilar metal coming in contact with water. Element A will replace element B somewhere else in the layout. When this has happened, very rarely, I have replaced the copper foil with a heavy gauge copper wire. 


Check the drainage under your switch.

Chuck


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## Greg Elmassian (Jan 3, 2008)

Yep, moisture and electricity and dissimilar metals:










These are parts of an Aristo #6 switch.

Greg


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## JPCaputo (Jul 26, 2009)

My 2cents, I would add a plastic strip between the 2 brass strips in that LGB switch. Just a thin piece of styrene will do, tacked iin place. This will safeguard against accidental shorts from unexpected things pressing the brass pieces together. Im one of those who believe Murphy was an optimist.


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## chuck n (Jan 2, 2008)

You don't need an external source for the electricity. Two dissimilar metals in water create their own electricity. That is what batteries are all about.

Chuck


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## Pete Chimney (Jan 12, 2008)

Here is the galvanic series for corrosion. Gold is the least susceptible, magnesium the highest. The farther apart the two metals on this chart, the more susceptible the corrosion of they are in contact, espeically with a conducting medium such as salt water. On offshore oil production platforms a series of large magnesium bars are attached to the legs. in this way the magnesium is sacrified in lieu of the steel members. From time to time the magnesium bars are replaced to keep the steel frame intact.


*Galvanic Series In Sea Water*


*Noble
(least active)*


*Platinum
Gold
Graphite
Silver
18-8-3 Stainless steel, type 316 (passive)
18-8 Stainless steel, type 304 (passive)
Titanium
13 percent chromium stainless steel, type 410 (passive)
7NI-33Cu alloy
75NI-16Cr-7Fe alloy (passive)
Nickel (passive)
Silver solder
M-Bronze
G-Bronze
70-30 cupro-nickel
Silicon bronze
Copper
Red brass
Aluminum bronze
Admiralty brass
Yellow brass
76NI-16Cr-7Fe alloy (active)
Nickel (active)
Naval brass
Manganese bronze
Muntz metal
Tin
Lead
18-8-3 Stainless steel, type 316 (active)
18-8 Stainless steel, type 304 (active)
13 percent chromium stainless steel, type 410 (active)
Cast iron
Mild steel
Aluminum 2024
Cadmium
Alclad
Aluminum 6053
Galvanized steel
Zinc
Magnesium alloys
Magnesium*


*Anodic
(most active)*


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