Good morning everyone.
Today we’re going to take a look at an important piece of industrial history.
During WWII it was common practice for Allied intelligence teams to examine downed and captured German aircraft in order to determine how they were constructed and if there was anything that could benefit the Allied war effort. What they found was that the German aircraft contained very large, high quality structural elements, and it was determined that these elements had been produced on large forging and extrusion presses that were much larger than anything existing in the Allied nations. The implications of this were immediately apparent. If forgings and extrusions that were large enough and of high enough quality to become key structural elements in aircraft could be produced in this country, it would lower the time and costs of fabrication and boost aircraft production output. Make more bombers faster, in other words.
The U.S. immediately started a high-priority project to construct a large press that matched the estimated capabilities of the German machines, and contracts were awarded to the Mesta Machine Company of Pittsburgh to build an 18,000 ton press, and others for the production facilities. Just about every part of the construction process was new, including the necessity of building the plant around the press due to its enormous size. The project wasn’t completed however, due to the end of WWII.
When all of the shooting stopped, Allied technical teams went into the German factories and found that the Germans had produced and learned how to operate die forging presses up to 30,000 tons capacity, and found that one 30,000, and two 15,000 ton presses were still usable. As part of the post war settlement, the Soviets got the 30,000 ton press and the U.S. got the two 15,000 presses, which were channeled into the USAF’s Heavy Press Program.
The Heavy Press Program didn’t really get started until 1950, after many months of planning and getting input from the defense industry. Since there wasn’t a consumer market for anything produced by the heavy presses constructed by the program, the government would own the facilities and rent them out to the contractors. Thus, Air Force Plant 47 was authorized to be built in 1952, located in Cleveland, Ohio next to the ALCOA plant, to house the 50,000 ton press that Mesta was making. The plant began operation on May 5, 1955, and that’s when the “Fifty” went to work.
The Super Giant
The Mesta 50,000 ton “Super-Giant” forging press is big. Everything about it is big. The press, called the “Fifty” by those who work with it, is 87 feet high, 36 feet below ground level and 51 feet above, and weighs in at around 8,000 tons. (Image #1) Some of the largest castings required over 350 tons of steel for the pour, and eight other castings weigh from 215 to 240 tons apiece.
On top of the underground foundation assembly are two upper and two lower base sections (Image #2). The lower platen is attached to these, and the lower forging die is clamped to the 12 foot by 26 foot platen. The upper platen is attached to the lower moving crosshead (Image #3), and with no dies on the upper or lower platens, there is 15 feet of clearance. Since the maximum stroke of the press is six feet, the forging dies it uses must be fairly large, to say the least. The entire moving crosshead assembly consists of eight steel castings that total nearly 1150 tons (Image #4).
Above the moving crosshead assemblies are the stationary crossheads (Images 5 & 6) that house the eight main hydraulic pressure cylinders. (Image 7)
Running through the press from top to bottom are eight massive alloy steel columns 76 feet long and 40 inches in diameter. The columns were forged from 270 ton steel ingots and machined on a 96 inch lathe. Each column was trepanned to remove an eight inch diameter core the full length of the column (Image 9). Four sections of each column were threaded and fitted with four steel nuts, each 52 inches in diameter, with eight of the largest nuts weighing 55 tons each. (Hey Louie, pass me the 51 and 13/16″ socket, wouldja?) Like I said, everything about this machine is big.
The press uses a hydro-pneumatic pressure system to generate it press force, using water with soluble oil as the working fluid. 1,500 hp motors charge four forged steel accumulators (Image 10) to 4,500 psi each, which is then released to the eight pressure cylinders mounted in the stationary crosshead at the top of the press. The combined effort of these eight cylinders produces 50,000 tons of force between the platens.
50,000 tons. I’ve used that number a lot talking about this big freaking press, but just how much is 50,000 tons, in something that you can visualize? Well, let’s see; the platens that hold the forging dies are 12 feet wide by 26 feet long, if you recall. If you had a steel bar that was 12 feet by 26 feet and 612 feet long, and stood it on its end on the lower platen of the press, that would be 50,000 tons of pressing force. My, my, what a vision.
At the end of the press cycle, the hydraulic force is reversed and the fluid is directed into eight pull-back and balancing cylinders that return the moving crosshead back to its starting position.
The “Fifty” was shut down in the summer of 2008 when engineers found stress cracks in the machine’s base. Much hemming and hawing was done by ALCOA, the operator of the press, on whether to rebuild or scrap the machine, as it was estimated that it would cost $68 million dollars to rebuild it. Pressure was applied by Senators and CongressCritters, as well as local government and unions, to fix it and preserve around 1,000 jobs. In 2009, ALCOA decided to rebuild the press after wringing out concessions and incentives from the interested parties, and it has just recently resumed operation. Which is a good thing, as most aircraft flying today have structural elements that were made on the “Fifty” before it broke down. Parts were made on the “Fifty” for the Space Shuttle when it was flying. While the big machine was down, a smaller 35,000 ton press was used as a backup, but it wasn’t an “ideal solution”, according to the operating company. Parts for the F-35 will be made on the big press, as well many other fighter and commercial aircraft. They expect to get another 50 years of service from the machine. Maybe I should have them take a look at my knees….
Many thanks and a huzzah! to jeepjeff for bringing this wonderful machine to my attention.
If you come across something that you think is of interest to our eclectic group of readers (and the dim-bulbs too. We’re nothing if not fair), submit your something to email@example.com.
The American Society of Mechanical Engineers – 50,000 Ton Closed Die Forging Press
The Library of Congress – Historic American Buildings Survey/Historic American Engineering Record
BoingBoing – Bringing a 50,000-ton forging press back to Life
The Atlantic – Iron Giant
Cleveland.com – Huge Mesta press is backbone of Alcoa’s Cleveland Works
Cleveland.com – Alcoa to rebuild 50,000-ton press in Cuyahoga Heights plant