The first group of these locomotives were built with 200 psi boiler pressure and a tractive effort of 16,700 lbs. The second group of locos had 225 psi and a tractive effort of 20,800 lbs. Factor of adhesion at that higher pressure 4.47.

For a locomotive 20' long and 8' tall riding on rails two feet apart, 20,000 lbs. is phenomenal. That is why we call her "Saddletank Superpower" !