Transition car.

Phill-

Anything is possible, but I think running 2-rail trucks on 3-rail tracks will be extremely troublesome. The biggest difference between 2 and 3 rail wheels is the profile - specifically the wheel flange. On 3-rail trains this flange helps the car navigate through track switches and tight curves without derailing; without this flange the car could only be run on very broad curves (O-72+) and high-speed switches (ex: #6 or larger).

Fortunately Atlas cars can easily be converted to run on 2 or 3 rail track by means of swapping trucks. Most cars have a screw in the truck bolster; when removed the entire truck assembly can be removed and swapped with another truck. Atlas offers numerous types of replacement trucks on its website (link here), which can be found in most local hobby shops. Requests to trade Atlas trucks do pop up frequently in the "for sale" and "wanted" forums, so you might even find what you need from another forum member.

Hope this helps!

John.

Phill-

I also forgot to mention this very helpful forum post from a few years ago; it is definitely worth reading.

Converting Atlas cars is very common; some dealers even offer to swap trucks when purchasing a new Atlas car.

-John

I use a transition car.  Lobster claw on one end and a Kadee on the other end.  All of my cars have high rail wheels through.

There are some here who use scale wheels... but your trackwork needs to be very good.

Have Fun!

Ron

I have a intermountain 2 rail tanker that is trouble free on Gargraves and large Ross turnouts

Our layout was 100% Atlas solid nickel silver track & turnouts. Everything was up-graded to Kadee body mounted couplers, with LOTS of 2-Rail freight cars. I rarely had any issues, once I modified all the guard rails on the Atlas turnouts. I added about .010" or .015" shim stock to the tops off all the guard rails, and the 2-Rail wheels worked a whole lot better, even backing through turnouts.

clem k posted:

I have a intermountain 2 rail tanker that is trouble free on Gargraves and large Ross turnouts

 

Yes, it is a matter of coincidental tolerances. Track like GG, which has a prototypical-ish near-flat railhead does well with "2-rail" trucks (GG makes 2-rail track). Real RR track is not flat on top; it is slightly curved, by design.

The 3RO switches and their flange ways can be problematic - too deep and too wide - but - some 2RO cars are OK with them. Try the car and test it as and where you will be running it before you do any conversions 

You can couple Atlas 2 Rail couplers to Atlas 3 rail couplers. 

Here is an example of an ACF hopper with 2 rail couplers coupled to ACF hoppers with 3 rail couplers.

Andrew