What would I need to reduce voltage going to a smoke unit?

One way is to use a diode(s).

Find the minimum voltage that produces the desired amount of smoke. Then use Dale H.'s method of a diode dropper to reduce 18v to the desired voltage. These may be a little big and they do get warm.  Although, just one diode may work, cutting the voltage in half to 9 volts. Most Lionel conventional smoke units start to work nicely at 7v - 9v.

 

Did you view Eric's Trains mod of the ice car effect? Shoot him an email to find his configuration.

I did see Eric's video and dropped him a note a couple of weeks ago but never heard back. I don' know much about diodes or rectifiers. i would like to keep it as simple as possible with maybe a basic diagram. 

Wire a 3A diode in series with the puffer unit, job done. 

 

The diode only has two leads, and it doesn't matter which way you wire it, so just cut one wire, splice the diode in, and run.

 

Radio Shack has them 2 for $1.99.

 

Considering you only need 1, U.S. mail order from the usual suspects (DigiKey.com,  etc.) will be more after shipping...though there's a recent thread in the Electrical forum about filling out a DigiKey order.

 

Or if you can wait a couple weeks, 3A diodes are 10 for 99 cents with free shipping from Asia on eBay (enter "1N5402" in search box).

All he did was repack it with more wadding and extend the fill pipe. Looks like the stock unit works ok. Watch from 17:09. Eric's Trains Ice Cold Express Review

Thanks for all the input guy's. I just picked up some diods from Radio shack and I'll put it in line tonight.