[Steve on Cattail Creek]

If you desire a large volume of 'smoke' and plan to run it for a longer time, you might want to consider an inexpensive ultrasonic transducer, which uses distilled water to produce a copious plume of mist. I've used them for two projects, the first a campfire simulation:

The second was to add 'smoke' as an upgrade to an old Menards burnt engine shed:

For both projects, the volume of mist was mechanically restricted -- the full output is quite impressive, and too much for my scenes! Both also used plastic containers fastened below the layout to feed the transducers, and I have yet to need to replenish the distilled water. I've had no problems with the mist affecting the surrounding layout or equipment, either, though to be fair on both points, I do not run either display for very long at a time.

I also just started experimenting with some small Suethe smoke generators, and so far, I'm impressed. They do run on standard smoke fluid, so constant use will put a lot of chemicals in the air, and require regular replenishment, with all that implies. I suspect even the smallest generator will produce plenty of smoke unless you're going for a scene from the Apocalypse, but adding a second smaller generator if needed/desired shouldn't be too hard. Good luck!

 

[Steve on Cattail Creek]

That looks interesting. Did you make it? I did a quick google and couldn’t find anything.

Edit: ahhh, ok. I’m starting to find them. The only problem is a lot of reviews say they seem to kind of be junk lol.

Can you recommend one that will actually last?

Dunno -- I've had mine for a couple of years now with no problems (at that price, you could probably afford to throw away a few duds!). Here's a pic of the type I used:

The lead from the transducer at top plugs into the circuit board in the middle, and the transducer fits between the two halves of the base, which are snapped together with the white wick (not shown here) filling the barrel and drawing water up from the source.

Here's a video I did of a bench test prior to installation of the first one, showing the plastic supply chamber in the background, and the block of wood I fabricated to mate the transducer to the plastic tube that both limited the output and directed it through the layout to under the 'fire' in the camping scene, as well as all the above parts (some obscured):

 

[Steve on Cattail Creek]

In fairness, I should mention one possible drawback: since the transducers produce a fine mist of water droplets, the 'smoke' being produced is not heated -- in fact, it rapidly drops below ambient temperature, due to evaporation -- and will only rise as far as momentum (from being mechanically flung from the transducer's surface!) takes it, and then arcs over and tends to fall (you can see the effect on the campfire video above). Thus, there is at least potentially a small realism gap for some applications, but with a little adjustment it can be minimized, and the other benefits remain.

 

[Steve on Cattail Creek]

Personally, I don't think that's much of an issue Steve. If you used a long enough stack it would be, but if you keep it relatively short, it seems to have plenty of velocity. I think this rivals most fan driven smoke units, and surely better than most Seuthe smoke units.

I tend to agree, GRJ, but I thought the falling 'smoke' might be an issue for some, and IME the installation generally requires a bit more fiddling and fabrication than some other options (like the Suethe smoke generators, which are drop-dead simple IMHO). In any event, IMHO it certainly belongs in the modeler's "tool chest" for use where appropriate.

 

[Steve on Cattail Creek]

Interesting. I have to look into that transducer unit. Thanks for the information.

No problem, and good luck, Kenny!

 

[Steve on Cattail Creek]

Im going to be putting into a building that’s “on fire” so I have a couple of concerns. One is the flow of the mist. That’s probably not a huge issue. I’m sure I could make it work with proper positioning.

The other issue that worries me is water itself. Being that the unit will be spraying in a small structure, I’m nervous of water buildup and subsequent damage of the structure and surrounding ground.

FWIW, I agree with GRJ's points. IMHO, you should not design a system with the outflow directed in or constrained by materials that would be water- or humidity-sensitive (I wouldn't use one in a cardstock or foamboard structure, for instance!), and I endorse your thought to position the output to direct the plume away from the structure

The closest I've come to dealing with the issue is the burnt engine shed installation, where I routed the output up into the 'well' that holds the engine. The mist tends to gather there, and is wafted out between the wheels by the fan, rather forming a plume. So far, I've not noticed any moisture or related damage in the vicinity, but just about everything nearby is plastic, and thus impervious, and as I said before, I haven't tried to run it for long periods.

Finally, unless you are operating in an area with very high humidity, IME the mist just evaporates in the air (leaving no deposits if you use distilled water as recommended), and does not create any noticeable water. As GRJ and I have said, the amount of water consumed in use is relatively miniscule, so I doubt you'll add enough moisture to change anything.

 

[Steve on Cattail Creek]

So I just have to figure out how to rig eventhing up in the “burning” apartment building. I wonder if I could get some tubing and run it to the top of the structure thereby avoiding water accumulation in general, and more specifically water getting on the LED’s.

Shouldn't be too hard. Dunno what your design is like, but if you have a hole in the roof, that's what I'd try first. I've never tried splitting the output, but that might be a possibility, though you might run into condensation issues in the tubing if you get too aggressive.

For my campfire scene, I used the hole I had earlier drilled through the layout (to run the leads to power an Evan Design flickering orange LED I added under the stock campfire piece) to route the plastic tube to just under the campfire. Distilled water (and any mist made from it) is a nearly perfect insulator, unless contaminated with salts, so I had no qualms routing the 'smoke' directly over the LED, which, to be fair, was pretty well insulated itself. Not even a hint of a problem so far . . . 👍

 

[Steve on Cattail Creek]

Ok. I ordered a 6 pack of those things from Aliexpress. It was like $1.62 lol. Should be here in a couple of weeks.

Good luck! If you want to follow the earlier thread (about a year and a half ago) when I went down the same path, here's the link: https://www.modeltrainforum.com/threads/ultrasonic-smoke-generator.203290/