Pushing or pulling.

[Taunton]

Sounds apocryphal? After all, the huge American steam locos, certainly by the time of transition, were mainly either mechanically fed or oil fired.

Not mainly but entirely. There was a Federal Railroad Administration regulation that fireboxes over a certain number of square feet had to have mechanical stokers. Still, the advent of diesels might well mean the end of the "helper district" and the jobs of the crews manning the bankers, so embarrassing performance on the hill was definitely in their interest.