A rivet is really just a hole with some metal put back into it.
Every one of them is a place where the material was interrupted, and interrupted material is where cracks decide to start.
Build a structure out of hundreds of them and you have hundreds of those places, each needing to be drilled, filled and then inspected for the rest of the aircraft’s life.
Which is a maintenance bill as much as a weight problem.
So the ideal is a single part with no joints anywhere in it at all.
The obstacle is that nobody can carve one economically.
Squeezing beats cutting and it beats fastening
There are three ways to get a complicated shape out of a piece of metal.
You can cut it away from a solid block, which works and wastes most of the block, and leaves the grain of the metal running straight through whatever curves you made.
You can build it from pieces and fasten them, which is cheap in tooling and expensive in everything after.
Or you can heat a block and squeeze it into a die, which is what a forging press does.
The advantage is not just the shape. Under that pressure the grain inside the metal flows and follows the contour of the part, so the strongest direction of the material lines up with the direction of the load.
A cut part cannot have that and a riveted assembly certainly cannot.
The catch is force. Aluminum at forging heat still resists hard, and the bigger the part the more of it there is resisting at once.
The machine that supplies the force
The press stands on the east side of Cleveland, and most of it is not visible from anywhere.
Roughly 87 feet of structure, of which about half is above the shop floor and the rest is sunk into the ground beneath it.
The frame alone weighs somewhere near 8,000 tons.
Eight rams push down through a stroke of six feet, working on hydraulic pressure of 4,500 pounds per square inch.
Rated capacity is 50,000 tons of closing force, which is where the machine gets its name.
It was made by a Pennsylvania machinery firm and started work on May 5 of 1955, under an air force program that paid for it.
What it makes and what stopped it
The best documented work on this press is not commercial at all.
It forges large aluminum structural parts for a fighter program: bulkheads that carry the wing and engine loads, weighing between 1,800 and 6,000 pounds and running 10 to 23 feet long, plus wing box components.
Those are the parts that replace an assembly. A bulkhead pressed whole does the job that a built up frame full of fasteners used to do.
In 2008 cracks were found in the structure and the press was shut down on safety grounds.
The repair was first costed at 68 million dollars. By the time it restarted in early 2012 the bill was 100 million.
The owner has changed name twice since, and the machine has been a listed engineering landmark since 1981.
Where the popular version overstates it
Two claims travel with this press and neither survives contact with the record.
The first is the jetliner. The documented output is military structure, and while the press serves commercial aerospace as well, a passenger aircraft wing spar squeezed here in one stroke is not something anybody has published.
The second is uniqueness. This is not the only machine of its size. A sister press of the same rating stands in Massachusetts, built under the same program in the same decade.
Even the height gets two answers, 87 feet in one account and 92 in the owner’s own, which is a suspiciously round disagreement.
None of that makes the machine less impressive, in the same way that figures around an expensive machine or a record vehicle get rounder with retelling, as the owner’s own announcement of the rebuild sets out.
Why a machine from the fifties is still the one
Nothing about the basic design has ever been superseded.
Force is force, and a hydraulic press that closes with 50,000 tons in 1955 closes with 50,000 tons today. What has changed is everything around it: the alloys, the die design, the heating, the controls.
Building a replacement would cost far more than the rebuild did, and the parts it makes have got larger rather than smaller.
The program that funded it was designed to give the country capability nobody could buy commercially, as the assembled history of the press records.
Seventy years on, the fighter bulkhead coming out of it is the argument for that.
So is the bill to keep it running.
