844 rebuild and specifications

Greetings

So after watching my 844 dvd for the millionth time I was wondering if after this huge rebuild does the 844 have different specs? For example her weight in working order. all of this new steel used to rebuild the firebox and all associated parts. I imagine that new steel is stronger and lighter than the steel used in 1943-44. So has her tractive effort been changed and tonnage rating?

thanks

unionpacific4018 wrote:...all of this new steel used to rebuild the firebox and all associated parts. I imagine that new steel is stronger and lighter than the steel used in 1943-44.

Sean,
I'd be rather suprised if the weight of the steel has changed much. With new technologies, you can get more uniform quality out of batches of steel, but it's going to weight about the same, since it's almost the same material.

Now, if they had made a titanium firebox, or something crazy like that, then there might be a weight difference, but even with that, I'm thinking that the bulk of the weight is from the frame and drivers. I never really thought about locomotive weight distribution as related to parts before.

This post raises some good questions. The weight may not be the main concern here. This engine was built during the war. The buff press has stated that various railroads had to use different grades of steel at that time. This was due to material shortages. Who knows what the shop that made the new parts used. It may be something not available to Alco, in 1944, or even not invented.

Sometimes there are corrosion problems when you put different metals in contact. You also wouldn't want to use a metal that had significantly different termal expansion properties (for instance) than the original for fear of setting up stresses where the new parts connect with the old. The old parts, as far as I know, worked well: I'd guess the U.P. engineering people would have replaced them with material as close to the original in its properties as they could easily get. (Easily: without paying a steel company an astronomical sum to cook up a batch to a since distcontinued recipe.)

It is true that some alloys were not available for steam locomotive construction during the war, and that this led to increased weight. The ATSF 2900 class 4-8-4 were virtually identical in dimensions to their previous class, but much heavier because of the metal used. (I suspect, but don't actually know, that a major part of the difference would have been with the boiler shell: prewar a nickel-steel, wartime carbon steel. But don't trust my guess on this.)