What is required voltage to run post-war DC?

I used to run our O-27  layout with a 12 volt automotive battery and rheostats during blackouts back in the 1970's just for the novelty. They ran OK from what I can remember. Three industrial/farm 6 volt batteries would probably be best for regular operation.

When powering with DC, your whistle/horn/bell will be always triggered. Vibrator motors will not function. The 3 pole pullmor motors will run on DC.

What's the max DC voltage I can put on a pullmor before I blow it?  And then I should do what 20% less?

The motor life is generally shortened by an inverse exponent of the voltage. And there are so many different "pullmor motors" for even more variation.

There is no magic number, but as a rough example, a motor run at 16 volts will easily last 10 times longer than at 26 volts, and at 26 volts 10 times longer than at 36 volts, and so on. 

Are you looking at doing some destructive testing to report back to us?

I'll wear safety glasses and have the fire extinguisher on the ready!  

As a newbie I'm staying conventional until I get the hang of this and engines are pretty cheap.  The old motors seem to be maintainable with abundant part availability... it's a childhood memory thing... and I'm not ready to drop a few $Gs for a DCS/Legacy system and a single engine (though I know I will!).

I'm playing with the concept of Bluetoothing some of my early engines for at least better sound (in tender or trailing car).  Some of my better looking/performing PW engines maybe I'd play with Blue Rail board if there were a way to handle the current and use their PWM output to control such a motor.  That's beyond me for the moment though.

All of what you want to accomplish can be done with traditional AC power... why DC?

I had read it runs a bit smoother with better low speed characteristics on DC... or maybe I read that wrong.  Kind of experimenting.

There was a guy on the other forum, but haven't seen him in a few years. I believe he ran dc but he had marx trains not lionel.