I have a Sunset 4-6-2 USRA Light Pacific, and it will easily go around 18" radius curves. However, mine has the four axle USRA tender, and not the tender shown in the OPs picture.
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As others have noted, this thing has poor pulling power. I plan to use it on a four car mail/express train of one 50 foot express reefer, one 50 foot express boxcar, and two 60 foot baggage cars. It is pretty well fully loaded with that.
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Pulling a circus train of 70 foot Mount Vernon flats and 86 foot heavyweights around 18 inch radius curves might be another issue.
I personally have one these locomotives, and in my experience, it is really finicky. Some of the tender wires came undone (which were a pain to fix), and when it does want to run it is kinda rough. Great display piece though with the rest of the set.
I have one of those Walthers engines. It ran like cr*p when I got it. I changed the tender, added all-wheel power pickup on the tender, did some filing on the trucks, and other things I can’t remember. It runs very nicely now and the original details are great. Today, I would probably consider a Bachmann USRA model.
