How DCC operator can make a mess and fix it

[carlso]

I feel sure that all of you have seen this malady before, at least those who operate on DCC layout.
This happened because the man with the throttle, that would be me, was not paying attention to a FVM SD60 parked on a siding. Somehow, ? ? ?, the loco creeped until it stalled out on a switch and sat and melted the lead truck. I have known this for several years now so just plain stupidity on my part.

Now the problem comes in with the fact the loco is a FVM SD60 and I have found parts impossible to come by. No replies to e-mails and yes I am aware of Matt's problem. Point is no new truck for me  for now. Can be patient!

I got to thinking about Matt's old affiliation with IM so I got a wild haired idea. I had some trucks out of an IM F3 that I mucked up a few years ago and thought just maybe. Guess what, the IM F3 truck looks identical to the FVM truck and one of them fit into the frame, revolved freely and ran smooth and quiet.

Wow, I missed stepping in a pretty big pile. Just passing on some 1st hand experience.

Happy again!

[Jim Starbuck]

Well played Carl!

It’s not what goes wrong but rather how we recover from it that counts.

[Cajonpassfan]

Ouch Carl, that is a mess😬
Glad you found a fix. What kind of short circuit protection do you have?
Otto

[peteski]

WOW! A good example of what can happen when high amperage is allowed to go through an N scale truck's front and rear driver (on the same side).
Since the high current was only passing through the wheels and the metal bearing/pickup plate, no fuses inside the model would have prevented the meltdown.  And obviously the total resistance of the "short" was high enough to just pass enough current to melt the delicate truck components, but not high enough to trip the DCC breaker.

[narrowminded]

WOW! A good example of what can happen when high amperage is allowed to go through an N scale truck's front and rear driver (on the same side).
Since the high current was only passing through the wheels and the metal bearing/pickup plate, no fuses inside the model would have prevented the meltdown.  And obviously the total resistance of the "short" was high enough to just pass enough current to melt the delicate truck components, but not high enough to trip the DCC breaker.

Is this something that a frog juicer would have prevented, correcting the polarity automatically?

[nkalanaga]

"was not paying attention to a FVM SD60"

I thought SD60s, like all SDs, had 6-wheel trucks?

[samusi01]

It's a GP60... I did the same thing with one of my FVM SSW (or SP? don't recall) GP60s.

The Intermountain tip is a good one.

Sam

[carlso]

N K - When I type, I hunt and peck, and often my fingers don't do what my mind is thinking but
          yes it is a GP60.

Thanks to all of you for the comments.

Otto - the layout has Digitrax P42's, I think that is the #, but they do not work well and we have not been able to adjust them to keep this from happening. To me the real bad deal is the loco was sitting on a stub end siding inside of my refinery and somehow I turned the throttle knob to "1" and it crept to the switch. I am fixing my sidings tomorrow with toggle switch to totally deaden the siding.

Great sport,
Carl

[Cajonpassfan]

Thanks, Carl, for the explanation, but I still don't get it... 
Even if you put an on/off switch on this spur, there surely are many other spots on the layout where a car or loco could short? I'm not familiar with Digitraxx, I have NCE, but if your DCC system doesn't trip a short reliably, you need to have something else between it and the track that does, like a DCC Specialties PSX or even an automotive bulb to draw the current. Or are we saying this can happen anyway?? (I did have a similar situation, melted a Kato passenger truck axle on a switch, before I installed the PSX's. Haven't had this problem since, and sure hope I won't in the future!)
Otto

[carlso]

Otto,

If you are not familiar with Digitrax and do not use it then you are the smart one. Our club established 8 years ago as a total Digitrax layout because they gave fantastic discounts on all of the products they sell including decoders for members. A one time only deal and IMHO we fell for it. We have had issues with their DS64's, P42's, as well as other items. Their manuals are all POS's. Try reading one and then understand what you read. We have not been able to get "help ? ?" from Digitrax at all because many times they will say "I don't know" maybe you should try this. But we made our bed and do the best we can. We are currently working on other manufacturers products to see if we can do better.

Perhaps we should go to the old reliable 1157 12v auto bulbs, they work.

As far as the toggle switches go, inside my refinery the locos will be safe on a non powered siding.
yes the problem will still exist on the rest of the layout.

[tehachapifan]

I was under the impression (hoping?) that this sort of thing only happened with early DCC.

[peteski]

Perhaps we should go to the old reliable 1157 12v auto bulbs, they work.

The bulb current limiter might not have prevented the damage (or at least some damage) either.  Depending on the resistance of that "short", there still could have been some appreciable current conducted through it (and through the short).  Also, 1157 is a dual filament bulb and I suspect you would use the higher wattage filament as the current limiter.

[mmagliaro]

Protecting circuits with an 1157 is one of those "sorta kinda" solutions.

The 1157 spec is 2.10 amps at 12v.

So in the case of a dead short through a loco truck, 12v is dropped across the 1157, 2.1 amps will flow, and unless that's
over the DCC booster breaker rating, it won't trip and the truck will melt.

What about a partial short (which is most likely what happens in these truck-melt cases)?
Suppose 6v is dropped across the lamp and 6v across the truck?   Incandescent lamps are not linear devices, so it won't draw half the current.  Let's say it draws only 1/2 amp?   Well, that's better, but might still be a lot of current to pass through a thin contact strip in a loco, and could still be enough to make it get really hot and melt the truck.

The answer is, "it depends" on how much of a short is created in that truck.  Sometimes the in-line lamp might save you, and sometimes not.  And incidentally, this same problem could plague a plain DC system, although it would be less likely, simply because the track voltage is very unlikely to be all the way up to 12.

[daniel_leavitt2000]

The trucks from IM, FVM, Atlas are all interchangeable. Micro-Trains may also be compatible. Some modern Kato truck are as well though they usually have different shaped contact strips. LL/Walthers uses very similar mounts and work gear though the truck gearbox and internal gears are totally different, they still work in Atlas, IM and FVM chassis.

[nkalanaga]

Carl:  Considering some of the things that have been done by railroad shops, it's possible that there IS a 4-axle SD60 somewhere.  It couldn't look any stranger than an 8-axle C40-9, in Conrail paint, in Brazil.