How do I slow down my big Alco?

Change the motor wiring from parallel to series.

The other way is to get a bridge rectifier, tie the "+" and "-" leads together and hook the remaining leads in series with one of the leads that feed the motors. This will drop the input voltage to the motors by 1.4 volts in either direction which will slow the motors slightly. You can use multiple bridges to drop the voltage further. This allows you to keep the motors in parallel which will prevent one from stalling and having the other one slip which is the down side of series wiring.

It seems like Atlas engines are build to run optimally at a scale 55mph (out of the box). I was devastated when I first realized this but a good friend and mentor, Ben Brown, showed me how to re-wire them for dramatically better performance.  I haven't experienced any of the stalling Matt mentions and have all of my engines wired in series now. The engines run much smoother....its an obvious difference you will notice right away. Another thing to do is add weight to the engine. I add 16 to 20 oz per engine (yup- that much with fishing weights). Once you remove the Atlas electronics, there is loads of room in there. The extra weight seems to add to them running smoother. They will pull a lot more as wheel slip is minimized (O scale is heaver than you think). Next break them in....pull some long heavy trains if your layout allows it. Run the engine(s) for a few hours....put some miles on it. This will break in the gearing and everything else. Periodically clean the inside of your wheels where the bronze piece contacts the wheel. Lubricate that when done with some Labelle electrically compatible  grease. Keep your wheels clean with denatured alcohol. 

Another upgrade for DC is constant headlights. If you want constant headlights, use the existing Atlas LEDS. Get some 470 ohm 1/4 watt resistors, simple on off mini switch, 9V wire harness, and 9V battery.  Wire the Atlas lights to the battery with the of on off switch in between. Next mount the switch under a roof mounted fan for easy access. 

For a dummy without headlights, pick up some 3MM warm white LEDS, 470 ohm 1/4 Watt resistors, 9V battery, wire harness and a single pole on off switch from Radio shack. Tape the LEDS into place and mount the switch under a fan as above. 

Having over 20 Atlas DC engines in my fleet running heavy trains every week, I can vouch for quality and durability of the Atlas product. I am fine with the China drive design now too.  With updated wiring, they are great even for switching (you must have frogs wired though). Look at my Youtube movies if you get a chance and you can see some of them in action....

I would like to check out your movies but don't know what your You Tube handle is in order to find them.  Please let me know or give me a link.  Thanks.

Phil Randall

TX

Mine run switching is the main reason for the C&O big Alcos, so it behooved them to go really slow.  I had limited success years ago with an Atlas Alco RS1  2 rail, converted to series wiring, but then I never really gave the machine a chance to break in.   Will try this again on the RSD7, as I believe this is about the simplest way to get where I'm going.  Keep yunz posted !   Gonna try a lot of extra weight too!

 Phil- here is a link to my movie page

http://www.youtube.com/user/Industrialmodels2

Hey Matt- I am not sure as I don't have anything set up to measure the current. I am running an MRC Power G and there aren't any meters on the unit. On the weight, I have been filling the fuel tanks with BB's and gluing in a 16 oz fishing weight into the engine compartment. Makes a big difference in pulling ability and seems to add to the slow speed performance......

It seem that my Atlas O locos (2 rail) pull about 1/2+ amps when I am switching.

Dick

I was looking at your videos with the consisted Geeps and they definitely were pulling smoothly. Are you running them under DCC or conventional DC?