I had 4 of the Atlas F9s. One was kitbashed into a B unit using a urethane shell I found at a show. They all ran 25-30 years on my layout with the original drives. I always ran them as pairs because they are light weight pullers. But with trucks that roll a pair was fine for 15 to 20 cars on my 1 1/2 percent grade. I shaved off the cast on grabs and put on wire ones, and move portholes to make F7s and I filled in the pilots.
I never had a failed gear or any other problem with them. The second pair was sometimes a little jerky due to gearlash I think when running light. I never had a sideframe fall off either. But the sideframes are a flimsy assembly I did break one while do maintenance.
I also had a pair of the original Intermountain GP9s which had a copy of the same drive. Those had a little more gear lash, but again no broken sprockets or gears or whatever.
I think for a home layout, they work out OK as a low priced power source.
