I run my layout on DC. I make no regular use of Lionel OO locomotives other than the one I own that was re-powered by a prior owner (I did not do the dirty deed!). Dick G. however wrote with news that he got his Lionel locomotive to run on DC. I will let him tell the rest of the story.

I have a OO3 Lionel 2-rail locomotive with a whistle in the tender. My dad bought it used, and gave it to me for Christmas when I was a boy in the late 1940s. This is the reason I’m interested in OO gauge. I also have the original Lionel instructions for it. There is a wiring schematic and explanation in the instructions.

The drivers on the left side of the locomotive pick up current from the left rail. The tender wheels on the right side pick up current from the right rail, and transfer it to the locomotive through the banana plug in the locomotive cab. There is a chrome plated spring jumper bar on the bottom of the tender that touches contacts on both truck assemblies. The screw holding the jumper bar in place supplies power from the jumper bar through the screw to the whistle motor.

For my experiment, I removed the jumper bar, and reinstalled the screw. With the jumper bar removed, no power is transmitted to the whistle motor. Also with the jumper bar removed, only the front tender truck picks up power from the right rail, and transfers it to the locomotive through the banana plug.

I clipped wires from my DC power supply to the ends of the rails on my test track. The locomotive and tender began to move with about 8.5V. DC. At 10V. DC, the locomotive and tender ran at moderate speed. The instructions say that about 8V. are needed to move the locomotive and tender, and up to 14V. are required when it is pulling cars. I ran the locomotive and tender a number of times in each direction.

When I pressed the reverse direction button on my DC power supply, the locomotive stopped. When I pressed the reverse direction button again, the locomotive ran in the opposite direction. It is the “E” unit (reversing mechanism) under the boiler in the locomotive that is actually reversing the direction of travel. When I interrupted the current once, the “E” unit indexed to a neutral position. When I interrupted the current a second time, the “E” unit indexed again and reversed the direction of travel. This is how the “E” unit works on AC.

I also tried backing out the thumb screw under the cab roof. I think it disables the “E” unit or reversing unit. (With the thumb screw screwed in, a point on the end of the thumb screw touches two contacts on wires.) The schematic calls the thumb screw the “E” unit switch. With the thumb screw backed out, the locomotive wouldn’t do anything on DC. I can’t explain why at this point.

If the tender does not contain a whistle, no modifications would be necessary to run the locomotive on DC. If the tender has a whistle motor, you have to disconnect the whistle motor to get the locomotive to run on DC without the whistle blowing continuously.

I also have a new Lionel motor. Some time ago, I tried running it on DC. As I recall, when I reversed the direction of the DC current, the motor ran in the same direction. You need a bridge rectifier or a reversing switch to reverse the direction of the motor as you have discovered.

Tonight I looked over the original Lionel instructions. I never noticed this before. It says “Lionel ‘OO’ gauge trains operate on low voltage alternating current (A.C.) or direct current (D.C.). … Storage batteries may be used with non-whistling outfits if house current is not available. Two six-volt batteries connected in series will deliver 12 volts which will be ample for the operation of the outfit. No. 91 Rheostat will be required for speed control.”

Now I don’t understand why guys that are smarter than I am remove the Lionel motor and “E” unit (reversing mechanism) and install a permanent magnet DC motor. I almost bought a modified Lionel locomotive so that I could run it on DC.

As to why modify a Lionel locomotive with a new drive, that is a good question. Perhaps the original motor was damaged, perhaps it was just the natural inclination to modify things to try to make them better.

UPDATE: Dick G. had two more notes. One was that it was helpful to know that the the Lionel OO whistle motor operates on DC provided by the Lionel 167X whistle controller and he also adds that

The whistle motor lead wire has a connector on the end with a threaded hole. This threaded hole acts as a retainer or nut for the screw that holds the jumper bar in place. I pushed the whistle motor lead wire connector aside to disconnect the whistle motor. Then I installed a #2-56 nut in place of the whistle motor lead wire connector, and reinstalled the jumper bar and original #2-56 screw. Now the whistle motor is disconnected. This is all that is necessary to convert a Lionel OO tender with a whistle motor so that the locomotive and tender will run on either AC or DC.