K Line Smoking Caboose Resistor Size?

Running TMCC or Conventional?

@cjack posted:

Running TMCC or Conventional?

Excellent question because the one thing I was warned about is that how may people have destroyed a smoking caboose running with command control typical 18V on the track.

Example topics https://ogrforum.com/...e-caboose-smoke-unit

https://ogrforum.com/...s-and-k-line-caboose

Link with pictures showing the damage that can happen https://ogrforum.com/...81#82945629844587581

I'm not trying to tell you not to use the smoke unit, but you specifically said with your son. The last thing you want is something cooking off and melting.

Bottom line is, the stock system may have not been ideal, many people modified it or flat out switched to something entirely different.

Sorry, he runs in command.

@dennish posted:

Sorry, he runs in command.

Given that, I would either recommend not running with smoke or this might take experimentation to find an ideal value.

This is now a bad example given new information in this topic, you could use the common 27 Ohm standard Lionel typical smoke resistor, however in command (18V on the track) you want to half wave feed that through a suggested 3A diode.

But even then that might lead to overheating. So then say you use a higher 30 Ohm resistor plus diode or maybe even higher value, but many of those are then not the uncoated wire wound style so they get hot but may not smoke well.

I know, none of this is the happy easy answer you might have been hoping for.

My advice is forget the smoke or consider changing to a small fan driven unit.  By the time you get that K-Line smoke unit producing decent smoke, it's getting hot enough to melt the sides and/or roof of the caboose around the smoke unit.

The original value of the resistor was 62 ohms @ 3 watts, but for conventional running only.

@Chuck Sartor posted:

The original value of the resistor was 62 ohms @ 3 watts, but for conventional running only.

That sounds good. I figured maybe a 5 Watt resistor, running 18 vac would result in about 64.8 ohms. With no regard for heatsinking.

What do the new Lionel cabooses use for a ckt? Running command they seem to put out a wisp of smoke and nothing melts. Fan driven smoke unit as GRJ suggests?

So far I've found this control for caboose smoke...

For smoke, you want to have the resistor underrated, it has to get a lot hotter than the normal 125C temperature in order to produce smoke.  That's why the smoke resistors are typically rated at 2-3 watts, even though they are running them at 5-8 watts.

I need to learn to check this forum before I flip the switch from off to on. Note that the switch was in the DCS position. I will follow the advice and not turn it on until I replace it with a fan unit.

note that the second picture it is smoking sitting on the workbench a good minute or two after I removed it from the track

I just got one of these and am also concerned about a meltdown when running in command @ 18-20v track power.  Would it be possible to wire in a voltage limiting resistor before the smoke unit to drop the voltage down to something more appropriate, but still maintain smoke functionality?  Any idea what value resistor might work?

You don't want a resistor, that will dissipate more power than inside the smoke unit!  You're just moving the heat to a different place!  A diode in series will cut the power roughly in half, that will bring you down into reasonable ranges with 18V track power.

Good answer! Is there a schematic on the smoking cabooses that had the conventional/18 vac switches?

@cjack posted:

Good answer! Is there a schematic on the smoking cabooses that had the conventional/18 vac switches?

I don't know of a schematic, but my guess is that the K-Line caboose probably did something like a diode switched in.  If the K-Line caboose wasn't such a PITA to take apart, I'd pull one of mine apart and see if it's just a diode as I suspect.

Would a 9.1v 0.5w zener diode work?

A plain silicon diode is what you need, it cuts the full-wave track power to half-wave.  Don't over-complicate this.

What value of silicon diode would be appropriate?  I have little experience using them.

Just a 1N4003 will do fine, you shouldn't have more then 300-400 milliamps going to the resistor.

Excellent, thanks for the help