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

Paul
If you really want to make a super lightweight  shaft you can 3D
printing in titanium alloy . Today's metal 3D printing  are fantastic
and you can make a honey comb structure in the areas that needs most
strength. Machining will soon be past as with a metal 3D printing you
can have whatever shap and internal structure you are. The latter the
biggest advantage as machining complicated internal structures is very
difficult unless you can open the structure.
Also material waste is very low compared to machining

Roderick Scotto

The question is;  how long does it take?

I made some 3D printed intake manifold patterns years ago and it took up
to 24 hours.   Time is money.

BTW the whole exercise was futile as a p-port gave 50 more HP and was
MUCH! MUCH!!! lower cost to build.

Paul Lamar

I love 3D printing and use it semi regularly for non critical parts and prototyping, however, there is a little too much hype by the media and those with strong financial interest. Don't believe for a second the hype that 3D printing will replace traditional manufacturing. At best case scenario, you are looking at 10% (still huge numbers)

Case in point. printing metal at 0.002" resolution (poor resolution for any parts used in high precision application), requires 500 passes for every 1" of built hight. Each of these passes by a modern 3D metal printer is about a minute each. So for every inch in height requires 500 minutes of production time or over 8 hours per inch. Assuming you print an E-shaft laying on its side, we are talking about roughly 5 inches or 40 hours continuous printing or 1 complete week if you are running 1 shift or 2 days if you are running 24/7. These tools cost between $1 million and $2 Million each, so if you have a 250 day work year, and assuming 4 years to amortize the tool, every single day costs you $1,000 to $2,000 just for the tool.


The metal powder used is approximately $100 per Kilo depending on the alloy. Furthermore, the parts will need "support structures" that are printed, and then have to be mechanically removed. Of course with 0.002" layers, you will likely require significant post print machining and even then you have a good risk of having small voids in the metal. when you crunch the numbers, a 3D printed E-Shaft will end up costing over $10,000 (and I am probably underestimating it).

Making things worse, this process does not lend itself well to economics of scale.... in traditional manufacturing, you can drop the cost by orders of magnitude with volume, but not so with 3D printing. Based on the above rough numbers, under best case scenarios, the parts that are printed will cost about 10X more than parts that are manufactured in traditional methods in medium to high volume and the delta increases with increasing volume

If you are simply printing a prototype intake or exhaust manifold (I use 3D printing precisely for this application), then it's OK for one off designs (dimensions are not critical so at least you eliminate the post printing processing

Now, if you are Airbus or Boeing where every Kilo of weight over the life of the 30 year life of plane will cost you say $30K or more in fuel cost, then the extra cost of light-weighting the components can be well justified

Again, I am a strong proponent of 3D Printing but not of the hype the media and wall street likes to generate

Simon Saba

Thank you very much for the education on 3D printing Simon.

Paul Lamar

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