What is this thing?

I think I still have a bunch of fuel line and probably a collection of aircraft hoses and fittings if I didn't give them away to the guy that got my camaro.

I don't know how you'd seal salt into the bend well enough for that one.

So back in the day, I was still trying to get into another union job before the Local rep crushed that idea... long story... but one of the things I trained for with the Union was a pipe bending cert. Like I was trained for oil pipeline bending machines for the big stuff. There is a rolling mandrel that gets shoved into each pipe by the boom loader. Then the bending operator guides the tube in place on the dies, instructs the boom operator on how to position and twist the pipe. The main job of the bending operator is to get the mandrel in the exact spot in the dies every time and secondarily, to get the bend in the right spot. The mandrel itself expands ahead of and behind the actual bend and there are a series of additional segments that expand but are not locked. The pipe itself has a maximum bend specification, but that does not include the seam which must be avoided and limits the total potential complexity of each bent section of pipe.

There are similar mandrel bending machines for higher end automotive exhaust tubing manufacturerers but they are like one person type operations. Those generally use a simpler mandrel from the big machines. The old skool hotrodder technique for bending tube for headers is with pitch tar. One can fill the tube and let it freeze and then it will bend like a single unit. I just hate the smell. I worked for around 2 years as an operating engineer at asphalt plants and was around and covered in the junk a lot. I've bathed in diesel fuel more times than I care to count. It is the only solvent that gets the stuff off your skin and clothes. The only thing that motivates me to think about playing with pitch again is how it is used for grinding DIY optics for telescopes, but dental plaster works too apparently.

For my tubing, I decided to completely redo by bedside laptop auxiliary side stand from scratch and that frees up a lot of space. I went down the rabbit hole of designing a 3d printed pleated air filter today. I have tried to make one once before a year or two back, but it is surprisingly challenging. I didn't see a single one on Thingiverse or Printables, so I must be the only one dumb enough to try and turn a tee shirt into an air filter, or make air filters to any shape or dimension of an air box. I could do the K&N style easily. Those are just a pleated wire mesh with medical gauze in between, but I want zigzag pleated fabric with nothing in between and no need for oil.

Finally the idea came back... for tube bending with 3d printing, I was going to try printing disks with a ball joint like pivot in the center and a nylon string or steel cable running through the center of the disks. That is similar to how some simple mandrels work with tube bending. You leave enough slack in the center string to allow the maximum bending range of motion desired. Then on the end of the mandrel, you need a cam lever that can pull the string over center and taunt. The amount of tightness can regulate how the metal/plastic/substrate moves in the bend. The more complex mandrels basically add multiple stages to this scheme where the front and back sections clamp tighter. Anyways, that is on my way back burner of things to try one day.