Another Bachmann K4 bites the dust

[Rich_S]

I don't own this model so I'm making some assumptions. I assume that the tender has all-wheel pickup.

This sounds to me like the loco was allowed to sit at some location on the track (probably a turnout or auto-reverser) where the same side rails were at opposite polarity.  The differing polarities were either between wheels on the same truck or between the front and rear truck. If the resistance of the electric pickups in the tender was high enough not to trip the throttle's (DC) or command station's (DCC) breaker (but low enough for higher current to pass through the tender) then the high current caused the electrical path of the short in the tender to heat up and melt.  At this point the damage is severe enough where it affect electric pickup. At least this is what I think has happened.

Peteski, I'm not 100% sure how the pickups on the tender work? The trucks have cups that the axle ends ride in like most diesels. These pickups have a small bus bar that extends up into the tender body. I know the Sound Decoder is mounted in the tender, but I do not know if these bus bars contact the bottom or side of the Sound Decoder? There are also brass wires that contact the frame of the locomotive and the front tender truck bus bar.  See this drawing http://www.bachmanntrains.com/home-usa/dwg/dwgs/NSCALEK4s4-6-2_TENDER.pdf

At this point I'm wondering if something shorted out in the Sound Decoder as the locomotive was performing flawlessly before yesterday. Also to note, all of my switches are Atlas code 80 with plastic frogs and every inch of my layout passes the quarter test without any delay. Also the melt down occurred on a straight section of track.

Anyway the locomotive is already on it's way back to Bachmann, so we shall see.

[Rich_S]

Achievement unlocked! 

Secret smoke unit.

Cool But now how do I keep the tender on the rails since the leading tender axle is now a permanent part of the undercarriage and the truck side frame is at a ninety degrees angle to the rail 

[Chris333]

Since it is DCC     The power from the locomotive drivers goes to the tender through the drawbar. Those drawbar wires usually rub the inside of the front tender truck contacts. Then the power would go to the decoder. Decoder to motor via. wires.

[peteski]

Peteski, I'm not 100% sure how the pickups on the tender work? The trucks have cups that the axle ends ride in like most diesels. These pickups have a small bus bar that extends up into the tender body. I know the Sound Decoder is mounted in the tender, but I do not know if these bus bars contact the bottom or side of the Sound Decoder? There are also brass wires that contact the frame of the locomotive and the front tender truck bus bar.  See this drawing http://www.bachmanntrains.com/home-usa/dwg/dwgs/NSCALEK4s4-6-2_TENDER.pdf

At this point I'm wondering if something shorted out in the Sound Decoder as the locomotive was performing flawlessly before yesterday. Also to note, all of my switches are Atlas code 80 with plastic frogs and every inch of my layout passes the quarter test without any delay. Also the melt down occurred on a straight section of track.

Anyway the locomotive is already on it's way back to Bachmann, so we shall see.

If you are 100% sure that the loco was fine and suddenly died on a solid piece of straight track than this is a mystery to me. Especially since only 1 axle was affected.  I took a look at the drawing and the truck sideframes contact metal strips riveted to the decoder PC board.  If something was shorting on the decoder itself, why only single axle was affected? If in the beginning (for whatever reason) only single wheelset was conducing most of the short-circuit current and it melted then one of the other wheelsets (the 3 on the tender and the drivers on the loco) shoudl then conduct the high current and also start heating up melting.

Plus you said that even after the meltdown you were able to write to CV 8 to reset the decoder and that it would function when you put pressure on the tender.  That would seem to indicate that the decoder was still fine.  But on the other hand, there might be some hidden damage (like melted wire harness in the drawbar and possible some other damage (inside the tender) to the contact strips for the other tender truck.

I would have liked to see a photo of the damage and even the tender taken apart to see if there was any internal damage. But that would have probably voided the warranty.  Sending the model to Bachmann seems like the easiest and best way to get it fixed.

[davefoxx]

Achievement unlocked! 

Secret smoke unit.

Haha!  But, unfortunately, Bachmann apparently put the secret smoke unit under the tender floor.  Useful for modeling a hot box, perhaps? 

DFF

[Rich_S]

If you are 100% sure that the loco was fine and suddenly died on a solid piece of straight track than this is a mystery to me. Especially since only 1 axle was affected.  I took a look at the drawing and the truck sideframes contact metal strips riveted to the decoder PC board.  If something was shorting on the decoder itself, why only single axle was affected? If in the beginning (for whatever reason) only single wheelset was conducing most of the short-circuit current and it melted then one of the other wheelsets (the 3 on the tender and the drivers on the loco) shoudl then conduct the high current and also start heating up melting.

Plus you said that even after the meltdown you were able to write to CV 8 to reset the decoder and that it would function when you put pressure on the tender.  That would seem to indicate that the decoder was still fine.  But on the other hand, there might be some hidden damage (like melted wire harness in the drawbar and possible some other damage (inside the tender) to the contact strips for the other tender truck.

I would have liked to see a photo of the damage and even the tender taken apart to see if there was any internal damage. But that would have probably voided the warranty.  Sending the model to Bachmann seems like the easiest and best way to get it fixed.

Peteski,  You have your time line backwards. The intermittent running started yesterday. I wrote to a value of 8 to CV 8 yesterday and had the same issue of intermittent running. I then wrote 36 to CV29 Yesterday and reprogrammed the engine number into CV17 & CV18 yesterday, still had intermittent running. Also note, while this was happening, I tested the layout with another DCC locomotive and had no issues with the other locomotive. Tried to run the K4 this morning trying to further diagnose what was happening and that is when the tender axle and side frame melted.

Up to this point I've not had any issues with track or other locomotives. My layout is a simple loop on a 24" x 80" hollow core door with a passing siding and some industrial spurs, no reverse loops. Now my passing siding is dead. What ever happened to this locomotive appears to have effected the turnouts on both ends of the passing siding. Something strange is afoot and will take some detective work to figure out.

All I can say is, yesterday I had a fully functioning layout and today I have a locomotive on it's way back to Bachmann and a dead section of track?   

[peteski]

Peteski,  You have your time line backwards. The intermittent running started yesterday. I wrote to a value of 8 to CV 8 yesterday and had the same issue of intermittent running. I then wrote 36 to CV29 Yesterday and reprogrammed the engine number into CV17 & CV18 yesterday, still had intermittent running. Also note, while this was happening, I tested the layout with another DCC locomotive and had no issues with the other locomotive. Tried to run the K4 this morning trying to further diagnose what was happening and that is when the tender axle and side frame melted.

Up to this point I've not had any issues with track or other locomotives. My layout is a simple loop on a 24" x 80" hollow core door with a passing siding and some industrial spurs, no reverse loops. Now my passing siding is dead. What ever happened to this locomotive appears to have effected the turnouts on both ends of the passing siding. Something strange is afoot and will take some detective work to figure out.

All I can say is, yesterday I had a fully functioning layout and today I have a locomotive on it's way back to Bachmann and a dead section of track?

Ok, thanks for the clarification.  I suspect that there is a pretty good chance that the problem you now have with the layout is directly related to the melted truck in the K4.

[Rich_S]

Ok, thanks for the clarification.  I suspect that there is a pretty good chance that the problem you now have with the layout is directly related to the melted truck in the K4.

I think I may have jumped the gun too quickly. I now thing the two issues are unrelated and just circumstantial. When I started construction on this layout a number of years ago, I broke all the rules, as in unsoldered rail joiners, only a handful of feeders. I think this bad planning finally came back to haunt me. If I run jumpers from the main track to the passing siding and check everything with my fluke, all is OK and no shorts. So now it's time to add jumper wires to the passing siding and quit relying on the rail joiners and Atlas turnout points    One of these days I'm going to redo this layout and add jumpers to each section of flex, that is as soon as I get a Round-Tuit.   

[robert3985]

I think I may have jumped the gun too quickly. I now thing the two issues are unrelated and just circumstantial. When I started construction on this layout a number of years ago, I broke all the rules, as in unsoldered rail joiners, only a handful of feeders. I think this bad planning finally came back to haunt me. If I run jumpers from the main track to the passing siding and check everything with my fluke, all is OK and no shorts. So now it's time to add jumper wires to the passing siding and quit relying on the rail joiners and Atlas turnout points    One of these days I'm going to redo this layout and add jumpers to each section of flex, that is as soon as I get a Round-Tuit.   

I bit the bullet and got a "Round-Tuit" six years ago, and put a 6" 22AWG solid-core copper feeder on every steenking piece of rail on my layout!!  No more dead rails.  Track power is now not dependent on flimsy NS railjoiners. Ripped out all of my rat's nest DC wiring at the same time, and replaced it with high-speed-low-drag DCC wiring.  MUCH SIMPLER, MUCH BETTER!

Photo (1) Red feeder wires positioned in their appropriate holes, waiting to be stripped, tinned, fluxed and soldered to the underside of every piece of rail on my layout...


Yes...it WAS worth the effort

Cheerio!
Bob Gilmore

[up1950s]

Ooo look tube worms with a sunburn .

[nkalanaga]

JMaurer1:  Not all steam smoked:

The Swiss Electric-Steam Locomotives
http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/swisselec/swisselc.htm


There have been commercial live steam models built on the same principle, using track power to heat the water.  I know it's been done in O, seem to remember at least one HO model, but doubt that anyone has tried it in N.

[nscaleSPF2]

Peteski, I'm not 100% sure how the pickups on the tender work? The trucks have cups that the axle ends ride in like most diesels. These pickups have a small bus bar that extends up into the tender body. I know the Sound Decoder is mounted in the tender, but I do not know if these bus bars contact the bottom or side of the Sound Decoder? There are also brass wires that contact the frame of the locomotive and the front tender truck bus bar.  See this drawing http://www.bachmanntrains.com/home-usa/dwg/dwgs/NSCALEK4s4-6-2_TENDER.pdf

At this point I'm wondering if something shorted out in the Sound Decoder as the locomotive was performing flawlessly before yesterday. Also to note, all of my switches are Atlas code 80 with plastic frogs and every inch of my layout passes the quarter test without any delay. Also the melt down occurred on a straight section of track.

Anyway the locomotive is already on it's way back to Bachmann, so we shall see.

Rich,
Out of curiosity, what brand of DCC controller are you using?  If one of my engines encounters a turnout that has been thrown incorrectly, for example, my MRC will immediately shut down power to the track, and tell me that there is a short.  If a wheel derails and gets caught in the turnout points (causing a short) then the entire system immediately shuts down and no harm is done.  Can't tell you how often this has saved my equipment.

As far as the pickups on the tender go, they work a little differently than other Bachmann tenders.  Instead of those "bus bars" as you call them contacting long, springy copper fingers that are attached to a circuit board in the tender, the K4 tender uses much shorter, stiffer copper fingers that actually lift the frame of the tender.  You can verify this by carefully pressing down on the tender and notice the vertical movement.  Perhaps Bachmann did not have room for the long, springy, fingers. 

Anyway, when I removed the shell of the tender from mine to install a MT coupler, I noticed that one of the short, stiff fingers was twisted a bit.  I straightened it out, but I'm thinking that it's possible that if the force applied to the bus bar is not vertical, as it should be, then one or more of the bus bars may have contacted something that it should not have.

This is all speculation on my part, of course.  I am sure that Bachmann Service can fix your loco for you.

[Rich_S]

Rich,
Out of curiosity, what brand of DCC controller are you using?  If one of my engines encounters a turnout that has been thrown incorrectly, for example, my MRC will immediately shut down power to the track, and tell me that there is a short.  If a wheel derails and gets caught in the turnout points (causing a short) then the entire system immediately shuts down and no harm is done.  Can't tell you how often this has saved my equipment.

Jim, I have a Digitrax Empire Builder DCC system. I'm surprised the system did not trip, as every section of my track passes the quarter test with ease.  Every engine I have that shorts on a turnout not properly lined does trip the Digitrax circuit breaker, cutting track power and sounding the beeping alarm until the short is corrected.

This is why I think something inside the decoder shorted causing the wheels to heat up and melt the plastic axle, the entire event happened very rapidly, maybe within 2 seconds.

[robert3985]

Ooo look tube worms with a sunburn .

Haha...yup....and that's only the near-rail bunch.  There are an equal amount of far-rail feeders (in black) too

Cheerio!
Bob Gilmore

[Nato]

                  I' am sure you will simply receive a new replacement locomotive, that is what Bachmann sent me when my second K4 had the drive rods come apart. When it happened on my first one they actually put it back together as shown on the work order they send you when it is returned, the order with locomotive  two read "Replaced Locomotive."                                                      Nate Goodman (Nato).