The humble beginnings of something BIG; JU-03!

[finiteparts]

Feb 5, 2024 11:35:44 GMT -5 richardm said:

Quite amazing that the von Ohain experimental engine made it to 10 K given the technology of the time. Could all those calculations be too restrictive?... Did Ohain ignore all those numbers and just gave it a try and succeed?
May be you could just go the Ohain way ... about the same way way you see it. Give a try staying safe.

See above discussion.  The sheet metal model that is shown was never able to run self sustained.  The claim is it got to 8000 rpm and "overheated" in one book and in the other, it is claimed "When the engine blew up, Professor Pohl insisted that further experiments should be permanently relocated."

von Ohain did call his demo engine, "a working model born of optimism".   He is also quoted as saying, "It was not possible for me to build a model with high tangential velocity which could demonstrate performance capability.   I could afford only disks and blades of constant-thickness sheet metal. The maximum tangential velocity was set at 150 m/s.   At high tangential velocities, the blades would have been flying about our ears!"

His professor actually commended him on his theory and  calculations, but they were on performance and not mechanical design.

[Johansson]

There is very little information to be found about his early engines, but you are right in that the numbers are for the HeS2. My book mentions it being made from rivets and sheet metal but that is probably only the outer casing and not the rotor.

Guess I´ll be the first to make one then.

I will figure something out, making tapered steel discs is an option.

[Johansson]

Is there a program that doesen´t cost an arm and a leg for making these calculations?

It would be interesting to try different materials and shapes and see if it is possible to make a rotor that can survive decent revs from stacked sheet metal. I might abandon the sheet metal rotor idea at some point but I am not fully convinced just yet.

[finiteparts]

Feb 7, 2024 0:29:59 GMT -5 Johansson said:

Is there a program that doesen´t cost an arm and a leg for making these calculations?

It would be interesting to try different materials and shapes and see if it is possible to make a rotor that can survive decent revs from stacked sheet metal. I might abandon the sheet metal rotor idea at some point but I am not fully convinced just yet.

There is an educational disk design tool that was put out by the University of Cincinnati that is pretty neat, once you get used to the user input files.   It has some weird quirks, but it will allow you to play with the disk shapes to get an understanding of how the weight placement impacts the stresses.

You can download it here:

gtsl.ase.uc.edu/T-AXI/BD%20Suite%20Website/index.html

It also has a blade designer program T-BLADE that helps with understanding blade angles and vectors.   It is neat little learning tool....not sure how accurate....but definitely worth a try.

Below is a screenshot...there are sliders on the right hand side that allow you to change parameters and by watching the colors on the disk web you can see if it will meet the stress requirements.



If I try to think the disk near the bore, you can see that it starts to go red, which means that it fails to meet the fracture criteria for the material selected (A286 steeel).



If I change it to Inco 718, then I can meet the yield requriements, even though I don't quite meet the Safety Factor (SF) of 1.1.

The best part is, the price is right...free.

There is some documentation that comes with it, but I could also try to do a tutorial video and put on YT if needed.

I used the DEFAULT_INPUT.din file on this run and this is what I set the input to:



I get some warnings and I am not sure of the actual values, but it gets you started.   You do want the dead weight on the rim and then you can get to the screen shown above.

Good luck,
Chris

[finiteparts]

Oh....there is also a 3d view that keeps the coloring so that you can see where your stresses criteria fail...






There are only a few typical materials selectable, but if you need to, you can add your own materials....I haven't played with that, but it is there.

- Chris

[Johansson]

Thanks a lot for the link to the program! Unfortunately I don´t own a PC but I will save the zip file and try it out when I can get my hands on one.

This is really interesting, I had no idea that there were such forces involved in the rotary parts we use.

I am waiting for the registration to an IPSC handgun match to open in 3 minutes, then I am heading out to the workshop to cut aluminum for the diffusor housing!

Cheers!
/Anders

[Johansson]

I got half way through making the diffuser cover when I called it a night, when it is finished and welded I will clean up the edge and make a thinner mild steel compressor cover.



/Anders

[richardm]

Nice work! Too bad the strength and stress numbers are taking your performance expectations down a bit. But who knows? It could be worth it.

[Johansson]

I have been thinking about the future of the engine and I have decided that once (if?) it is running properly I will build a 1940 style Indy car with spoked wheels and leaf spring suspension around it.



If I can get 150hp out of the engine it will be plenty enough, John calculated the engine to produce >400lbs of thrust at 10.000rpm which translates roughly to 400hp from a freepower coupled to it.

So I really only need half of that power, which might not be very far away even with the RPM restrictions that these rotor parts put on the engine. Heck, 100hp and leaf springs is probably exciting enough on a gravel road.

After all this is a steam punk project, if I wanted max power I would just build two JU-02 engines and feed the massive freepower turbine that John sent me a couple of years ago. 500++ hp easily.

/Anders

[richardm]

That would be quite something Vintage style car with a gas turbine ! It would be like a Sopwith Camel with a turbo prop haha

[Johansson]

And a big, fuel thirsty, sheet metal behemoth as well. A small efficient gas turbine whistling along under the hood wouldn´t suit it at all.

With only 50% of the revs perhaps the fuel consumption won´t be quite as terrible as John calculated, 12.5 L/min at full throttle was what he predicted. It might settle for 5-6 L/min which is pretty ok, a 60 liter fuel tank will get me to the nearest village and back.

[wannabebuilderuk]

This but with your engine would look great ha

[Johansson]

The last piece of the puzzle, had this been the final stone layed in a church I might have praised the Lord. Had it been the final stone layed in a synagogue I might have sacrificed a child. Being what it is I will just make a cup of tea and watch the last part of the Tucker/Putin interview.



An overview.



Have a nice weekend!
/Anders

[richardm]

Are you gonna gite a little powered spin and enjoy the breeze That will hype you up!

[andym]

Feb 9, 2024 15:06:43 GMT -5 Johansson said:

The last piece of the puzzle, had this been the final stone layed in a church I might have praised the Lord. Had it been the final stone layed in a synagogue I might have sacrificed a child. Being what it is I will just make a cup of tea and watch the last part of the Tucker/Putin interview.



An overview.



Have a nice weekend!
/Anders

Dam...... that looks epic....