UP's 844 Rolled By

[Sumpter250]

Cast steel frame + all roller bearings have a lot to do with that.
What I find amazing, flabbergasting, astounding, is that that piece of industrial art cast frame - really the heart of the whole thing - has been in *constant* service pulling real load at higher speeds for 65 years. Given that steam locomotives are much rougher on themselves than diesels, that's astounding . Overall a testament to a solid modern-steam design by Alco.
The above amazement assumes that the frame has never been exchanged with one of the part donator FEFs. Does anyone know this for sure? How many times have the cylinders (part of the cast frame) been re-lined?

All of the "wear points"....those contact points where one item moves against another.... have replaceable bearing surfaces, which are inspected and replaced often. Even the journal boxes, ( driver axel bearings ), have renewable bearing surfaces between them and the actual frame. Combined with the equalizer rigging, that evenly distributes the driver weight on all axles ( even pilot and trailing ), there's not as much stress on the frame as you you might suspect.
A diesel locomotive frame, sits on two support points, one for each truck. there's a lot more vertical stress on it than on a steam ;locomotive frame.