I don't know how you guys could group the AA's and the AHS's together as original technology. Bethlehem Steel made the prototypes and set up the test venues, with cooperation of Penn State, and I sure wouldn't be surprised to hear that Carnegie/Mellon wasn't closely associated due to the brilliant minds being right there in Pittsburg. It was at the end of WW2 and things had to happen FAST. I don't know the whole story, but I do know that there are Bethleham boilers, Boston Boilers, and plenty of Axeman/Anderson boilers.
Note: AHS isn't on the scene until 1976 ish and it was called Eshland. I have 2 original Eshlands running right now, and dozens of Axeman/Anderson's. While they may not win any Beauty contests, their operation is a beautiful thing. Everyone that sees one refuses to believe that a unit that size can product 130K and 260K respectively.
As the newbies offer suggestions to improve, understand that these original guys were not dirt farmers who had no engineering background, they had just ended the greatest challenge the world had known: WW2.
They did have variable speed blower fan controls, ash removal systems, and infinite resources. Cost considerations dictated the final design and it is a beauty!
30 years later......Eshland came along, and proposed 'their take' on the AA design.
There were some stumbling blocks, and still are, as many of you know, especially the owners of the AHS product. There are subtle differences between the two, and many of you won't even know them for years. Let's just say: It's all about isolation.
So......do me a favor and in respect to the Axeman/Anderson folks, the AA is not an AHS, never will be. There are reasons AA's have an 'inclined auger' with a hole in the center......but that is enough here tonight. Suffice it to say, no one welds them better anywhere than Axeman/Anderson fabricators. You can drop a boiler blank out a C130 , clean it up and assemble the parts and fire it the same day. Crumple zones? Hell no. indestructible? Hell yah!!!
Also understand that Gentleman Janitor, EFM, Keystoker, Iron Fireman, Van Wert, Yellow Flame, Walker, and who knows how many others already had or were starting to built their versions of a stoker boiler.
I'd love to see all the history of Coal as a fuel, and the equipment used to utilize the most reliable heat in the Industrial Revolution; and it's use to our current times.