I finally inserted bridge rectifiers into my two conventional Lionel steam locomotives (starter set 0-8-0 and a 2002 4-4-2). Placed a single 4 amp rectifier in each locomotive, with rectifier in series between E-unit and motor. I used the methods mentioned by many of you...diagram available here: https://www.dallee.com/PDFs/MotorDiodeDrop.pdf
The results: modest smoke increase in the 4-4-2, with noticeably slower, smoother startup. This locomotive has a Seuthe unit, so I'm still experimenting with different fluids (including Seuthe that I use in Marklin HO locomotives).
The 0-8-0 responded very well, with nice slow startup and smoke belching at moderate speeds. (In the 0-8-0, I had already replaced ceramic 27 ohm resistor with an 18 ohm wire wound).
Nothing new here, but thanks to all who encouraged the use of diodes to improve performance.
