71–80 of 196 posts
Earlier quoted context omitted.
Spoked wheels aren't cast because it's hard to machine them. You can easily CNC them if you really want. But that would be insanely expensive and wasteful and not any better.
Yes, I said “impractical”, not “impossible”.
> The spokes are really hard to make precisely with machining
That is not true.
What strikes me is how great of an investment this turned out to be. Does the US invest in manufacturing like this anymore? Tangentially, if there were a war today would the US be able to produce as much as it did in WW2?
No, but that is different from not investing. Today the US invests more in automation and engineering and less in manual labor.
> if there were a war today would the US be able to produce as much as it did in WW2?
It took several years to ramp up to WW2 level production. We would see the same, a couple years of trouble on the fronts while building industry at home, then when the industry is built up massive production.
Historians (amateur so I'm not sure if they are right) tell me Hitler was ready for WW2 first and Italy begged him to not start the war as their industry wasn't ready. However France and Briton saw the war coming and were building their industry and so waiting might have made things worse.
These massive presses are/were of strategic importance. Something politicians, most of whom seem to be lawyers these days, completely fail to grasp. I am not in general a fan of government subsidy, but I was very disappointed when the government of the UK declined to fund a large press in Sheffield, which would have been used to build the next generation of nuclear reactors. June 2010 timeframe. Luckily natural gas i…
They are actually now directly govt owned as of 2020, with future investment for a new heavy forge.
> Forgings have the added advantage of variable grain direction which generally can be tailored to the stress patterns of a specific design. This is a super underappreciated fact! It's often repeated that forging is just stronger, but just squishing steel does NOT make it stronger. Forging a part is so much more than just smashing it into a shape. Steel cable is made of pretty ordinary steel which is stretched 100s o…
just squishing steel does actually make it stronger, because it increases the number of dislocations in its crystal structure. smaller grains mean higher strength even without the variable grain direction. also, peening, which is not exactly the same as forging but is also just squishing steel, can give you higher strength for a third reason: areas with residual compressive stress can't initiate cracks until you overcome that stress, which increases strength. even more, though, it increases fatigue resistance
Earlier quoted context omitted.
Castings can achieve shapes that are impractical to machine. A classic example is a spoked wheel. The spokes are really hard to make precisely with machining, but fairly straightforward when casting. Bandsaw wheels are virtually always cast, for example. Also, the processes are not really independent. It can be much cheaper to do a rough casting, and then machine just the critical faces of it, instead of using an “of…
Spoked wheels aren't cast because it's hard to machine them. You can easily CNC them if you really want. But that would be insanely expensive and wasteful and not any better.
Earlier quoted context omitted.
For context, I work on my car a bit, and the shop manual for it is hundreds of pages (thousands?). Now scale it up to a factory, maybe without manuals. Disassemble, crate it, assemble it 5000 miles away. Based on my software experience, I can sort of go in blind and figure out how a system functions. I suppose that translates to real world too..
There’s a UX school that says that if the user needs the manual you fucked up. I mostly subscribe to that school. Mostly. It drives my family nuts that I will assemble a piece of furniture without reading the instructions. But the thing is with a little mechanical sympathy, and a well designed product, there’s only one sensible way for the parts to go together, and if you organize them right while you disassemble it…
Machines are extremely complex, and that's before you even touch electronics and hydraulics, both of which are highly complex systems. Simply moving large machine parts safely requires documented procedures, let alone order of assembly.
> Forgings have the added advantage of variable grain direction which generally can be tailored to the stress patterns of a specific design. This is a super underappreciated fact! It's often repeated that forging is just stronger, but just squishing steel does NOT make it stronger. Forging a part is so much more than just smashing it into a shape. Steel cable is made of pretty ordinary steel which is stretched 100s o…
This effect also applies to polymers! Perhaps even more so. Take a polyethylene bag (LDPE) and stretch the material in one direction. You might notice the material becomes thinner but also stronger. This is due to the polymer chains becoming aligned. Eventually you get "drawn fibers" where the molecular strands are aligned with the fibers for optimum tensile strength.
What strikes me is how great of an investment this turned out to be. Does the US invest in manufacturing like this anymore? Tangentially, if there were a war today would the US be able to produce as much as it did in WW2?
Furthermore, all presses mentioned in the article have been surpassed by a 60,000 ton press that opened in Los Angeles, in 2018.
People with agendas will happily feed others narratives about the US not investing in manufacturing anymore, but it isn't true.
US manufacturing output has been steadily increasing since always, with the occasional 1-3 year dip during recessions. However, manufacturing does represent a lower percentage of our GDP with each passing year, despite the absolute value increasing.