The One Man Turbofan

[monty]

Ok guys....here goes: win loose or draw I'm going to make this crazy thing.

If it melts down into a pile of scrap, at least it will make an entertaining YouTube video. I've been collecting parts in anticipation of being able to make some progress over the Christmas break. I should have some time starting after about the 17th of Dec. So far I have the material to make the rotating components for the core and some stuff for the fan side, but my basic goal is to get the core rotating assembly done and finish the design of the castings, so I can start making all the forms before I have to start back at work after the 1st.

Below you can see a 3D printed fan. The orange parts (except the fan blade) will be machined from aluminum, the blades carbon fiber. The blades fit the hub nicely, so I'll go ahead with designing the mold for them. I'm going to make them using resin transfer molding. The orange fan blade is the pattern I will use. It needs a lot of surface prep first! Under the fan you can see the stator for the starter/generator. It will probably need to be rewound...

Also you can see the core turbine and compressor.

There are some gear blanks, and a 3d printed ring gear- fits nicely. Blanks must be heat treated and lapped together.

Helmet added for size comparison

On the way is a M11X1 tap and die, a brand spanky new 7/16 reamer, some 1045 for the ring gear blanks, and some 303 stainless for the shaft bits.

Stay tuned for details.

[racket]

Hi Monty

Thats one fine lookin' fan , ............there'll be a number of "lurkers" following your build ;-)

Cheers
John

[monty]

John,

Hehe.....let them lurk!

She'll be a thirsty beast that's for sure!! Only useful for terrorizing buzzards and converting hydrocarbons into a smile.

If anybody want's to see how it "should" be done go check out Price Induction

Back when I gave up on this the first time - a long time ago. I ran the numbers for an ideal cycle and came up with basically what they have built. I knew there was no way I could build that with my resources, plus cost was going to be way too high.

Fast forward to today, and the technology available to the knuckle dragger in a shed has come a long way. I feel like I can at least make something work now. Perhaps not a Formula 1 V12...but the one-lung, flathead, Briggs and Stratton of the turbofan world...maybe.

Even if it's a miserable failure, I will surely learn something...and be entertained in the process.

Monty

[racket]

Hi Monty

Now that engine is a nice piece of work , but expensive I'd imagine , especially if they want it certified.

From one fellow knuckle dragger to another , go for it I say , theres nothing you're attempting that gets the hairs on my butt concerned, considering the abuse our engines have been subjected to at times without them complaining, I think the only unknown is the gearbox and fan, and you seem to have them covered .

I can guarantee you'll be "entertained" ;-)

Cheers
John

[Johansson]

Oh this is going to be so much fuuun!!!!!

[Deleted]

Me Like...... very interesting build

[monty]

I FINALLY had some time to work on the engine this afternoon. I turned the compressor seal bushing. Of course I had to do it twice when I ruined the first one. I had two reamers, one a 12mm and one a 7/16 in. Now you would think that the 12mm would have 12mm on it, and not .4XXX.....but I was wrong about that one!! Who labels a metric reamer in inches anyway!!!...

So I made two.... The good news is the second one turned out quite nice. Doesn't seem like much for an entire afternoon, but a large part of the time was spent futtsing around with the collet closer to get it running true, mounting tools, cutting stock, and being interrupted constantly.

Tomorrow I plan to turn down the turbine and hopefully get the front spacer/seal bushing finished.

The bushing is made from 303 stainless. It machines really nice. No work hardening. Chips were coming off a nice straw color and breaking in small pieces. Not a horrible deadly birds nest waiting to slice me open like a lot of stainless!!!

Monty

[racket]

Hi Monty

It must be feeling good to finally be cutting metal :-)

Yep , I know all about those stainless birds nests, everytime I have to machine out the 8 inch tubing I use for the 4th stage Allison wheel's shroud I'm confronted by it , scares the crap outta me , between the tool squeeling its head off and long tenticals of stainless trying to enstare me , its a horrible job that seems to take hours .

I'm looking forward to your Posts

Cheers
John

[monty]

Dec 17, 2018 22:50:14 GMT -5 racket said:

Hi Monty

It must be feeling good to finally be cutting metal :-)

Yep , I know all about those stainless birds nests, everytime I have to machine out the 8 inch tubing I use for the 4th stage Allison wheel's shroud I'm confronted by it , scares the crap outta me , between the tool squeeling its head off and long tenticals of stainless trying to enstare me , its a horrible job that seems to take hours .

I'm looking forward to your Posts

Cheers
John

Those evil blue razor sharp chips.....the squealing tool always on the verge of disaster. I HATE machining most stainless...If blue ever turns to orange and sparks.....you're sunk! That horrible grinding non-cutting sound....

And yes.....it feels great to be making chips!!!

Monty

[CH3NO2]

Subscribed! Cant wait to see this Monty!

[Feathers]

SWEET!

I've done a lot of work so far toward this exact goal. I'm working on a 300mm fan powered by a 25kW (~32hp) brushless motor.

Hubs will be aluminum and the blades are carbon fiber with carbon fiber filled nylon 3D printed core structures (they allow for a greater blade thickness and wider operating range)

Don't mean to threadjack but let me know if you're running into trouble. I've done wet layups to make similar blades, and am saving for a Tormach 1100MX that I can use to cut these aluminum tools. Similarly I will be proceeding on the final blades with a resin transfer molding process once I have aluminum tools plated in electroless nickel. I'm also replacing the CF-reinforced 3D printed cores with Rhoacell, something that isn't liable to leak and fill up with resin during molding.



www.youtube.com/watch?v=pw6GEDH8KBw

www.youtube.com/watch?v=__ufyRxeZik

Can't wait to see how this comes together!

Might eventually be able to really test the merits of kerosene vs agitated electrons

Regards,

- Feathers

[monty]

Dec 18, 2018 16:57:48 GMT -5 Feathers said:

SWEET!

I've done a lot of work so far toward this exact goal. I'm working on a 300mm fan powered by a 25kW (~32hp) brushless motor.

Hubs will be aluminum and the blades are carbon fiber with carbon fiber filled nylon 3D printed core structures (they allow for a greater blade thickness and wider operating range)

Don't mean to threadjack but let me know if you're running into trouble. I've done wet layups to make similar blades, and am saving for a Tormach 1100MX that I can use to cut these aluminum tools. Similarly I will be proceeding on the final blades with a resin transfer molding process once I have aluminum tools plated in electroless nickel. I'm also replacing the CF-reinforced 3D printed cores with Rhoacell, something that isn't liable to leak and fill up with resin during molding.



www.youtube.com/watch?v=pw6GEDH8KBw

www.youtube.com/watch?v=__ufyRxeZik

Can't wait to see how this comes together!

Might eventually be able to really test the merits of kerosene vs agitated electrons

Regards,

- Feathers

Hi Feathers!

Nice looking fan! I think fans are relatively agnostic about what spins the shaft. If I could get a motor big enough, and a battery that had enough juice it would certainly simplify things.

Monty

[monty]

Well today was not as satisfying as yesterday. I spent half the time trying to get the lathe properly set up.

First I made sure the collet set up was running true. It was!

Then I spent at least an hour fighting with the setup trying to get the turbine to run true.

Only to discover eventually that the 7/16 collet had two thou of runout and there was nothing that could be done about it. Somebody probably dropped it and didn't tell me!!

So I switched to the next size up, which was dead nutts true. Then I fought with the limited space, and carriage travel trying to make a left hand cut. Possibly the worst setup in the world for rigidity. I had to change the tool post, and the compound to a very ugly configuration. Plus the tool had to be sticking out way too far to clear the turbine..

A combination of the steel the shaft is made from, the lack of a rigid setup and the way carbide cuts led to nightmarish chips and horrible cutting. The surface finish was good in the beginning, but then the dreaded chatter arrived.....

Fortunately I know a few tricks....High speed steel to the rescue!! I was able to get the chatter out of the shaft, but I'm going to need to re-group. I need a high speed steel insert and a more rigid holder....stay tuned.

Monty

[monty]

Today was a much better day, even if I did spend the morning chasing tenths around with a 4 jaw chuck, a dead blow hammer, a sharpy and a dial indicator....

Then run the lathe to let it warm up....rinse and repeat. I finally gave up when I had the seal area on the turbine running out around 1.5 tenths, the bearing surface itself running out a little under a tenth, and the middle of the shaft about 1.5. I didn't think it was ever going to get any better. I really didn't want to do it this way, but with this lathe and the tools on hand I just couldn't come up with another way to do things.

I was rewarded with a very satisfying fit on the shaft. I had to use an extremely sharp HSS bit to cut whatever steel the shaft is made from. Carbide just required too much force and kept forcing the shaft out of running true. The nice thing about HSS is I was able to sneak up on the dimension. I got a nice fit better than the factory shaft for the compressor and the seal. If I had to use carbide where the last cut is fairly heavy and you just have to get the math right....You wouldn't have been able to drive a hypodermic needle in my bum with a jackhammer!! Fortunately I didn't have to do it that way and was able to hone the last couple tenths off the shaft.

And finally this assembly!!! Now I need an adult beverage.

Monty

[dieselguy86]

I emailed garrett a couple years back, and was told the shaft material is 4140 cr-mo. I tried machining a shaft for a project and had the same probs, carbide just wouldnt work. I didnt have any HSS tooling, but a nice sharp cutter was what i thought would work good. Glad to see my hunch was correct.

-Joe