GN had “Heater cars” equipped with two large steam generators (and water and fuel tanks) that were used with the pre-war electrics. The two short-lived postwar W-1 class motors had on-board steam generators. Milwauukee took two of their Little Joes (E-20 and E-21) and installed steam generators in the cab space on one end for use as passenger locomotives. The boilers were removed in the mid 1950s.
What’s funny about the Little Joes is that they were designed for use as passenger locomotives with maximum continuous dbhp produced between 24mph and ~35mph depending on how much shunting was used.
Milwaukee re-wired all of the Little Joes at West Milwaukee, so I suspect they made some changes to make them a little more freight-friendly. South Shore had to convert theirs to 1500 volts from the USSR’s 3000. The nine Milwaukee Joes built to 5’ gauge must have been re-gauged at Erie.
Checked a little deeper on GN’s huge W-1s. They did not have boilers, so “heater cars” were used as required. The W-1’s outweighed a Missabe 2-8-8-4…
The major change that I am aware of involved the shunting, where the amount of field shunting was increased, along with adding another tap. This change provides more power at higher speeds, useful for passenger and freight service.
What would have made the Joes more freight friendly would have been a change in gearing.
Back in the early 1900’s, my grandfather and others were nearly asphyxiated while on