wirewound ceramic resistors for smoke units

BoxcarBill and Jim Sandman here on the forum can supply various values of smoke unit resistors. Chuck Sartor as well.

6 and 8 ohm are common Lionel resistors used with the semi-smart smoke units that are powered by an 8VAC regulator.

Older engines with an 8057 smoke unit used a 27 ohm, which essentially produces nil smoke. They are powered directly from the R2LC board; no regulator.

I have replaced these with MTH 16 ohm resistors, or 18 ohm resistors. They smoke much better with the lower values.

Rod

Thanks, Rod....Just the info I was looking for!

Phil,

I used ceramic wire wound resistors that are 22 ohm and 25 ohm 3 watt ones and have used them in older TMCC engines. At first, they don't smoke well but once they heat up, they produce a fine amount that does choke you with all that smoke found in a MTH unit. Not knocking what the MTH units produce if you like smoke but these resistors work well in older Lionel TMCC steamers that had the 27 ohm ones that produce almost nil amounts.

I saw a post where someone took the 10W square wirewound resistors and broke the ceramic coating off to reveal wirewound resistors of the correct size for smoke units.  I'm going to give that a try, you can get them from Digikey for less than 50 cents each.

Ted, where did you find elements of those values? G

Digikey has ceramic resistors of all sizes and values.

Not the uncoated type when I looked.  They all had coatings.  G

George, he was talking about the ceramic coated ones, that's what I was talking about.  For uncoated ones, see my previous post, I ordered a few different values from Digikey of the 10W square ones, I'm going to break off the ceramic and see what I get.

John, I'd be curious how a 10 watt resistor works. I suspect it will not get as hot using a larger gauge nichrome wire. Typically to get the resistor hot enough to make smoke you have to overdrive it past rated power.

Pete

George,

I got those years ago when Bill Serratelli worked at Millburn Trains-now he works for Atlas. I think he got those coated ones from Digikey or Mouser Electronics. The coated ones work very well.

Remember, those square resistors are only 10 watts because they have a large heat sink, i.e. the ceramic shell.  They are much smaller and lower in rating when they're bare.  In any case, I figured it was worth a couple bucks to try it, I saw it mentioned as a very successful and inexpensive way to create a smoke resistor.

In truth, you don't really drive them past their ratings to get smoke, consider the standard 27 ohm smoke unit running on TMCC.  It gets half-wave rectified power, so in heating effects, it's about 9 volts for 18 volts track power.  That translates to three watts, and I'm sure those resistors are rated at least that much.

Ted, thanks.

john, no mention of coatings, I had assumed ceramic core.  My experience with coated versions with Lionel is they don't work so well.  The un coated are harder to find.  Remember dimensions of the element matter too.  Won't know what size you have until you open them.  Will be interested in what you find.  G

Could someone please explain the resistor ohm ratings?

I will admit I have never been good with electronics.

Now I followed a post by Rod and replaced the resistor in a Lionel TMCC diesel with a 16 ohm MTH and it works great. But I have no idea what the ratings mean.

Does a 16 ohm get hotter than say a 22 or 25 ohm?  I'm in for a little resistor 101!

Thanks!

When you reduce the resistance in a circuit, you increase the current, assuming the voltage to the resistor remains constant.  Increased current means increased power being dissipated in the resistor.  Increased power means increased heat being generated.

For the same type of resistor, and assuming the source voltage has the capacity to maintain the voltage, the lower the resistance value, the hotter it'll get, and the more smoke that will be produced.

With 16 ohms, you're down near the limit for the R2LC on a standard TMCC board, and that should produce plenty of smoke.

The relationship for DC circuit, V=IR, and Power=VI.  So as john said you can see current I goes up as R goes down.  So Power or heat in this case goes up.

Rod:  You mentioned also Jim Sandman & Chuck Sartor.  I'd like to contact them.  Can you direct me, please?