One of the best ideas I ever heard about making E-shafts is hydro
forming. That is where a hollow steel tube is put in a mold and
tremendous pressure is applied to form the lobes.  I suspect the the
tube is heated to high temperature first. I think a lot of steel car
and truck tubular frames are made that way. Stuff is made in minutes
not counting the heating time.

Paul Lamar

You can not heat it much as the oil/water would boil or carbonized.
Metallurgy and post heat treat I think. Body panels are also made
this way in steel or aluminium. For this a mold is installed a a
sheet is slipped in. An outer piece comes down and clamps the sheet.
Then high pressure liquid is pumped in which forms the sheet against
the mold or form. The the liquid is pumped out.

   Dale Davies


I would imagine you would need to start with 0.5" or 0.625" wall tube
to allow for the thinning during the stretching for the rotor
bearings and then allow a bit for final machine to dimension and then
heat treat and nitriding. Dale Davies

What range of pressure are we talking about here?

Paul Lamar


   I've done a bit of research into hydro forming.  I've been considering
   using it to form wing ribs.  I've seen in the literature pressures up to
   1000 atmospheres used for forming sheet aluminum.  I'm not sure what the
   pressures would be for forming steel tubing.  Maybe twice that amount?
   There's quite a bit of stuff on YouTube about the subject.

   I've looked a bit for a source for a high pressure pump that is capable
   of generating 1000 ATM but so far I've come up dry.  Even hydraulic
   jacks don't use any where near that kind of pressure.  Maybe a hydraulic
   multiplier pump could be built where a 4" diameter piston drives a 1"
   diameter shaft into a cylinder displacing the fluid inside at 16/1
   pressure ratio.  That should easily get you 1000 ATM.

   I just calculated that a 20 ton jack, with a 1.5" dia shaft, should be
   able to create 22,675 PSI using that method.

   I've seen several videos of people using a pressure washer to inflate an
   envelope made by welding the edges of two sheets of steel together.
   That might be a way of creating a poorly formed tank in a pinch but it's
   practically useless for anything else.

Mark LaPierre


Often the pressures used for hydroforming are created using intensifying cylinders.
This is a stepped hydraulic cylinder the pump pressurizes the big cylinder
which drives into the small one. It's like a brake system backward.
The pressure multiplies based on the relative sizes of the cylinders.

Bill Jepson

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