When the PV&T sold the class D’s to the Milwaukee Road, that wasn’t the end of dabbling in high horsepower units. Some of the more worn out class B1’s were being retired, so one of them – #220 – was pulled out of the deadline and sent to the Portland shops to be rebuilt.

What came out of the shops was the class B1x prototype; a 4-section articulated locomotive riding on 7 class B trucks:

weight

~750000 pounds

horsepower

7800 continuous / 5 minutes @ 10500

tractive effort

1062 kN

traction motors

4 @ 450 hp (end trucks)

10 @ 600 hp (middle trucks)

It turned out to be a too ridiculously powerful locomotive for the railroad; if not driven carefully, it rips out drawbars without blinking and it’s very good at finding lightly loaded cars in the middle of a train (by popping them off the track on a horseshoe or loop.).

It operated as a hill engine for about 28 years before the talgo joint between the center sections failed, then was remanufactured into a class II locomotive with the same road number.