Some of the classic locomotives could be very rough rider, particularly whe worn.
Adrian Vaughn relates how he rode trhe footplate for,a long diastance on a very badly worn GWR loco (Probably ntowards the end of steam when no seemed to care ) He virtually had to be lifted off onto the platform.
Some of the smaller locos, would "nose" quite badly at quite low speeds, because of their short wheelbase.
And remeber the infamouse Southerrn River Class tanks. A combination of indifferent track and locomotive, literally, cost lives.
Especially with an unsympathetic driver, a fireman's job could be absolutely exhausting But in those days it was considered to be part of the job in climbing the ranks fro cleaner to top link driver (If you were lucky and good )
In winter, roasted on side and frozen on the other!
Often IF you gat a chance to sit down for a few mintes, the seat wasm't even padded, just bare wood.'
Howard