I've see a lot of goofy stuff with trains over the decades but I had one last night that perplexes me. The rear truck of an Atlas C40-8CW came loose from the chassis, and caused a 3 unit consist to stall going into a tunnel. NO OVERLOAD CONDITION WAS DETECTED! As soon as I noticed my freight wasn't moving I hit the panic button and went looking for the problem. After fishing everything out of the tunnel, I noticed there was no rear truck on the lead loco. I found what was left inside the tunnel, stuck to the left rail. The actual plastic truck frame had melted down at the last axle. I mean melted down. You can't get the truck apart. It's "welded" like someone hit it with a hot soldering iron. The decoder and motor are still fine. I've already checked them out but the unit will definitely need a new truck. While I'm at it, I'm changing them both, just in case!
Yeah, I saw this once. This is the reason I always make a case for DCC friendly turnouts (not that this is what happened to you). DCC puts out enough power to the rails that it can melt the trucks on a locomotive if it shorts out the system and it doesn't trip the circuit. Jason
Any thing like that can happen. What that really shows is that the layout has very poor short protection. I saw a Kato F3 that had died on a turnout- apparently bridging the two rails near the frog. Front truck got hot and all that Delyn plastic melted in a horrible blob. Short protection matters.
Anything like that can't happen when you're still DC! (retreats back into bunker, bolts door, waits for artillery to stop) I am getting a DCC test system, by the way, next thing on my list is color TV and one of those phones with the light-up dials.
I had a Geep do that. The command station (DCC) went to beeping and shutting down. By the time I got down to the end of the layout where the Geep shorted at a turnout...the truck was history !! :-(
Thats like spinning your tires in deep snow. Keep the gas pedal to the floor...something is sure to happen sooner or later !!! ROFLMAO !!!
I know nothing about DCC, but can an ammeter be inserted into main track feed line? An ammeter (in a DC line) quickly shows a higher than normal current draw, which is what caused your truck(s) to melt down. My system is DC, but when I hear a change in engine sound, or the sound stops, a quick look at the ammeter then killing power if current is too high.
I once heard that some folks stick a 12 volt auto light bulb in series with one leg of the DCC feed. Normally there is not enough current to light it up and it stays off. When there is a short it lights up and adds a high enough resistance to the circuit to limit the current till you get things shut down.
Also it is my understanding that if your layout is not wired with heavy enough gauge bus wires that it can contribute to the problem. The system wiring produces a lot of resistance that somehow fakes out the short detector circuitry in the DCC system. That is why they are encouraging everyone to use 12 gauge wire when wiring up new NTRAK modules and such. For older modules that have not been upgraded they like to run an additional heavy gauge bus wire under the modules.
I had something similar happen while running on one of the local N-scale club's portable layouts. The systen was a top-of-the-line NCE wireless system, but there was no short protection other than what comes stock with the command station, so my U.P. Livestock Despatch shorted on a bad, non-DCC friendly turnout on one of the return loops, stopped the train and melted the lead truck on the Kato F3. Everything else was okay. This problem is indicative of one or more problems with your layout, and there's an easy way to check both if there's a problem or if you've taken care of it. First, in a properly protected DCC layout, this should NEVER happen. "Properly protected" means that the short protection that comes with your command station isn't sensitive enough, and every layout should have aftermarket short-circuit management panels installed for each electrically isolated power district. If your layout is small, then that should be considered to be ONE POWER DISTRICT and should be protected by a short-circuit management panel. What panel to purchase? They range in price from about 35 bucks to much more. On my DCC portable layout, I use the Digitrax PM42, which will protect 4 power districts and cost me about $65. A really good place to go to shop for and get some information as to which short management panel is appropriate for you is Tony's Trains here: http://www.tonystrains.com/products/type_powerprotect.htm The other possible problem with your layout would be that your wiring is substandard. I have no idea how big your layout is, but a minimum DCC Power Bus should be 16AWG, and ideally you should have 22AWG feeders on every piece of rail (rail, not track). My layout is equipped with 12AWG Power Bus cables, which are high-purity, low-ox, stranded (many strands) red and black zip speaker wire, but that's because it will eventually fill a 35' X 35' space with several hundred feet of track. Minimally, you should have feeders every 24", with the current/DCC Signal Loss problems being compounded with sectional track. Nickel silver is a notoriously poor electrical conductor which means it has a very high electrical resistance, and there is noticeable voltage drop-off even over just three feet through N-scale or HO rail, which can affect the speed of your engines. Sectional track and all those little thin nickel silver rail joiners (soldered or not) adds much more resistance and is one of the prime reasons it's not good practice to construct a DCC layout using sectional track. Those of us who use "best practices" for our electrical protocols, NEVER trust a rail joiner to conduct electricity. It's like cutting your garden hose and stuffing a soda straw in the middle of it, then expecting the same flow of water out the end. Multiply that times every 10 inches or so (using sectional track) and you can see what potential problems can arise. Sometimes, it's only one section of a layout that's got the problems due to a cold-soldered feeder or loose rail-joiner and the easy way to find out is to turn on you DCC system, then short the track using a quarter. If your master controller shuts down the layout, then there's enough current at that position to tell the controller there's a short. Keep doing this about every two feet on your trackage to see of your system turns off and then resets. When you reach a spot on your track where your DCC system doesn't shut down, then that's the spot you need to add a feeder to, or check to make sure all the electrical connections are still connected. If you know you have a problem, but there isn't a place on the layout your system doesn't recognize (turns off everywhere, then comes back on after you remove the quarter), do the same thing using a dime, and if that doesn't work, then try the same thing using the bronze electrical connection/bearing plate in your melted truck. Logically, you should be able to find the problem by shorting out your rails everywhere on your layout, then looking to spot bad feeders, bad rail joiners, or lack of sufficient feeders. Good luck! Bob Gilmore
It may not be that your command station is insensitive to detecting short circuits, it is because the command station is set for a higher current then it should be. Everyone wants/thinks they need the most power available. Five to eight amp systems are supplying too much power that is not needed. Using aftermarket circuit breakers that can be set low enough to prevent meltdowns of which I have had a couple, but allow you to run a triple headed train are necessary. You should have an ampmeter in the line so you will know what your locos are drawing so you can set the trip current appropriately.
This reminds me of something that once happened to me on DC on my dad's layout. This, incidentally, is an argument against hidden trackage, because the train was in a helix when I noticed that it was taking too long to come out. I turned up the power, waited a minute, and ventured under the layout to investigate. What I found when I reached it was that the trip pin on the lead unit (on a McHenry coupler, a Kadee knockoff) was hanging too low and had snagged the opposite polarity's rail on the outside of the curve coming into the diverging route of the turnout, and MELTED the coupler!
I like Russell's light bulb idea. I haven't done any math with it, but it sounds good in concept. Just make sure it's out in the open where you'll see it quickly.
Had a Bachmann doodle bug short out DC, melted the the trucks, but was using a converted power supply out of a old main frame computer. Judd Barton
This is correct. An overload detector (or circuit breaker, or fuse) works by detecting a high current. Current is inversely proportional to resistance. (Ohms law, V=IR). Thus if you have more resistance between the power source and the short, you will have lower current. Smaller wire and longer runs mean more resistance, mean less current, mean it's less likely the overload protection will kick in. More important than the wire gauge is soldering a feeder to every piece of track and not relying on rail joiners to pass electricity. Dirt and corrosion in the joiners means plenty of resistance. The difference in resistance per ft between 12awg and 20awg isn't really so great, but what using large wire does is buy you the required leeway for resistance in your feeders and your less-than-perfect solder joints and terminal connections. I'd say the melt-down problem can be even worse in DC than in DCC because often the voltage is lower, which also means lower current, so again your overload protection doesn't kick in.
Tell that to my ConCor M10000 that ran afoul of a switch and before I noticed it wasn't running anymore one truck melted.
