Smoke unit temperature

If you're making something that directly sets on the smoke unit, I suspect the printed part will not be appropriate.

What you made out of plastic, looks like it could be made with brass tubing and soldered together.

For MTH smoke units, I use the screw-in brass ferrule and solder a brass tube to it.

gunrunnerjohn posted:

For MTH smoke units, I use the screw-in brass ferrule and solder a brass tube to it.

John,

Do you know how hot a typical smoke unit gets? This is something I have not actually thought about? There are a lot of new 3d printing materials that can be chemical resistant and have a higher melting point than the early materials available.

I've never gotten inside, but I've measured around 160F on the outside of an MTH smoke unit running full tilt.  Obviously, one issue is if the fan ever stops blowing, it gets a whole lot hotter in a hurry, one of the arguments for the diecast fluid bowl.

If we can calculate or measure how hot the smoke resistor gets, it may give us some sort of idea the maximum temperature that could theoretically be reached by the smoke unit as a whole.

Not too long ago, I plugged in a 30 watt soldering iron, waited for it to heat up, and then touched it to a small amount of fiberglass insulation material soaked with some smoke fluid.  It smoked profusely.  I'm sure the tip of the soldering iron probably tops out at around 750 degrees Fahrenheit or so.

While I kind of doubt that a smoke resistor gets quite that hot, it's good for a starting point anyway??? 

gunrunnerjohn posted:

I've never gotten inside, but I've measured around 160F on the outside of an MTH smoke unit running full tilt.  Obviously, one issue is if the fan ever stops blowing, it gets a whole lot hotter in a hurry, one of the arguments for the diecast fluid bowl.

That high temp plastic seems to work okay. My only complaint is the screws strip out of body then its basically ruined. Unless you re tap them with a new screw.

I guess since the newer Lionel smoke units have the thermistors and the voltage drops when the are at idle. It might not be such a issue of overheating. They in a way have became self manageable. 

Has there been a discussion on the forum of the similarities between VAPE pipes and model train smoke units. The primary components used as vape fluid is Propylene Glycol and Glycerin the same major components of smoke fluid. Vape pipes generally operate between 212f and 480f give or take a degree.  As the temp increases above 400f the percent of potential carcinogens rises. As fluid boils away in our smoke units the temperature of the heating element goes up. I think this is good justification for a thermistor in the heater circuit to limit peak temps.    Surly we have a chemist on the forum who might shed some light and clear the smoke here.      I have a very poor tolerance for the smoke our locos produce and about the only time I turn it on is when installing testing or repairing smoke units.          j

Harry736 posted:

Does anyone know  the temperature that smoke units operate at?  I'm considering buying a 3 D printer to make funnels and tubes to retrofit  TAS smoke units to my 8776 C/NW GP 20.  I wonder if 3 D printers can make a these parts that will tolerate the heat put out by a smoke unit.

I used the plastic or nylon goal post shaped tubes I made shown here, and they worked well, but after time, they get burned by the heat where they attach to the smoke unit.  The gloppy stuff in pic 2 is the glue I used.

 The heating elements get between 350f and 500f  as the fluid boils off.  I bet a 20 ohm resistor running lean on 18v may go over 500f.  As the fluid boils off and the temp goes up the percent of carcinogenic compounds created goes up but the volume of VOCs are going down at the same time such that you see less smoke from the stack. So time to refill.  We need a chemist to step in here.

While I generally don't use silicon around electronics RTV silicone used for auto gaskets can easily stand the temps generated by our smoke units.  silicone tubing is available on eBay in sizes from 1mm to around 20mm it can also withstand the temps in smoke units. I found the 7mm tubing will sit in the brass fitting on top of a MTH smoke unit. I cut the tubing off so that it forms a good seal with the boiler at the stack opening.  If using RTV make sure it is completely cured before installing in a loco. You might even want to wash it before installing to remove any acetic acid that might be remaining on it's surface.    You can make molds for molding RTV with common modeling clay and scrape the clay away after the RTV cures.  What you can't scrape off soap and water and a stiff brush will get off.        j

I don't use RTV on smoke units as it's a PITA to clean off when you have to take them apart for maintenance.  It's not if you'll need to open up the smoke unit, it's when, especially if you actually run smoke any amount of the time.