Raptor Composite Aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Dexacare, Mar 28, 2016.

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  1. Aug 14, 2019 #1261

    BJC

    BJC

    BJC

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    “The easiest way to solve a problem is to deny it exists.” - Isaac Asimov

    Edit: Asimov not only was a writer of science fiction, he also was a college professor and had a PhD in Chemistry.


    BJC
     
    Last edited: Aug 14, 2019
  2. Aug 14, 2019 #1262

    Tiger Tim

    Tiger Tim

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    What type of prop is he using again? I know piston singles often have props that tend towards fine when oil pressure is lost (to aid with a re-start) though with this scheme I think I’d rather have one that feathers in a failure (as seen on twins and turbines).
     
  3. Aug 15, 2019 #1263

    dcarr

    dcarr

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    It's hard to tell exactly how the new shuttle setup works in the video, but I think there are essentially three chambers inside the shuttle. The center chamber contains high pressure oil from the governor and that oil enters the prop shaft through radial holes in the shaft. I believe this center chamber is isolated from two lower pressure "scavenge" chambers (one on either side) by areas with a very close fit with the prop shaft. The concept is that bearings at either end of the shuttle keep the shuttle centered to avoid the tight areas making contact with the shaft and serve as low pressure seals on the two scavenge chambers. The scavenge chambers are connected to drains to ensure that the oil escaping through the tight areas exits to the sump without building up significant pressure.

    On a separate topic, I had some concerns that the PSRU main bearings appear to be grease lubricated only. Is that viable?
     
  4. Aug 15, 2019 #1264

    rv6ejguy

    rv6ejguy

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    Yes, that's how I see the design working too. However the inner shuttle bearings are not press fit to the shaft and I believe oil will find its way past here into the outer housing. I also see the inner races spinning on the shaft which isn't a good design. Perhaps it's good there will be some oil there to lubricate the shaft against the inner races.

    Grease worked on tapered wheel bearings in cars but since there is oil in close proximity here, that would be a better long term solution.

    The next video will be interesting as he runs the engine again. We'll see how the drive and prop work.
     
  5. Aug 15, 2019 #1265

    rv6ejguy

    rv6ejguy

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    Prop is a MT MTV-5-1-D/LD190-53a
     
  6. Aug 15, 2019 #1266

    Scheny

    Scheny

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    For a single engine you accept a worse glide rate in exchange for the prop to work in start and go around conditions in case the governor fails (fail safe). In a twin you still have the second engine to deliver thrust so a single governor fail is of less concern.

    During engine out trainings in the DA42, we did some tests how behaviour changes at different settings. A wind milling prop consumes around 13% thrust, meaning in order to simulate an engine failure, we first put it to 0 thrust and after finishing the checklist set it to 13% thrust (it has FADEC) to simulate feathering. We never switched it off in reality, as we once had an incident where it would never start again due to an oil leak.

    As for your idea to have a single in feathering, this is a terrible idea and forbidden. They always must go to fine. I once flew a two seater where the governor broke during take off and went to max pitch. Only easy I could notice was that rpm stayed at 90% and vibrated and it almost stopped to accelerate short of rotation speed. I rejected take off immediately and was able to stop last second. I would have been able to take off, but surely not to climb...

    So you see, there are reasons for why we do things as they are since ages.
     
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  7. Aug 15, 2019 #1267

    BJC

    BJC

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    Many aerobatic airplanes have counterweighted propellers that go to coarse pitch upon loss of oil pressure. That protects the engine from (even more) overspeed during moments of reduced oil pressure.


    BJC
     
    Last edited: Aug 15, 2019
  8. Aug 15, 2019 #1268

    Tiger Tim

    Tiger Tim

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    Thanks BJC, you beat me to it.
     
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  9. Aug 16, 2019 #1269

    rv6ejguy

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  10. Aug 16, 2019 #1270

    flyboy2160

    flyboy2160

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    What? After all that's happened and been said, you were expecting something different?

    Given the abrasive nature of the courts I play on causing wear on my shoe soles, I can't even play pickleball for 2 cents a mile. :D
     
    Last edited: Aug 16, 2019
  11. Aug 16, 2019 #1271

    akwrencher

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    Wow. Just, wow.
     
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  12. Aug 16, 2019 #1272

    mm4440

    mm4440

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    In the United States, we have the First Amendment which protects our right to dream, engage in wishful thinking, exaggerate or outright BS.
     
  13. Aug 16, 2019 #1273

    mcrae0104

    mcrae0104

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    I want a 20 year loan on a depreciating asset that has unproven performance. Sign me up.
     
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  14. Aug 16, 2019 #1274

    Hot Wings

    Hot Wings

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    What, no offer to lend me money so I can buy a franchised dealership from them!? o_O
     
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  15. Aug 16, 2019 #1275

    flyboy2160

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    No. Fraud is NOT protected by the First Amendment. This is a general statement of law, not particularly being applied to anyone under discussion.

    One can also be found guilty of negligence if one ignores 'facts' that a reasonable man could determine.
     
    Last edited: Aug 16, 2019
  16. Aug 16, 2019 #1276

    rv6ejguy

    rv6ejguy

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    Since nothing has been delivered yet, only the gullibility of those who put down deposits so far has been demonstrated. I wonder how they will react when they find that the real acquisition, training, insurance and operating costs are many times the predictions you see here? Really, who could believe 8 cents per mile in fuel costs? Oh, never mind... 1500 people, I see that now. How silly of me.
     
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  17. Aug 16, 2019 #1277

    Tench745

    Tench745

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    I decided to compile a short list of features from the website that are not on the aircraft. These are only the ones I've seen so far.
    -Carbon fiber engine mount instead of steel tube
    -Automatic deicing/engine cooling in wing skins
    -All pushrod controls in the wings instead of cables
    -Internal hinges on foreplane instead of exposed hinges
    -4-bladed prop

    So, at the very least the website is not reliable.
     
  18. Aug 17, 2019 at 5:51 PM #1278

    BJC

    BJC

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    The first amendment applies to state actors. It is mute wrt wishful thinking, dreaming, etc.

    I’m not a state actor; it you were to work for me, I would have the right to constrain your speech while you were on the job.


    BJC
     
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  19. Aug 17, 2019 at 6:01 PM #1279

    pictsidhe

    pictsidhe

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    Those sealed bearings will hold slightly above 0psi oil pressure. They do a decent job of keeping oil inside prelubricated bearings, but not much else. No surprise that the thing leaked on it's first run...I don't really understand why he doesn't just seal up the housing and use a single drain from the bottom instead the kludged shuttle 'sealing'. The propshaft bearings can get lubed too then.

    I much prefered the original trim spring, it just needed to be properly designed and made. If I say what I think of it's replacement, a mod will be upset.
     
  20. Aug 17, 2019 at 9:44 PM #1280

    Voidhawk9

    Voidhawk9

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    Indeed. It appears he is 'forced' to such measures as his composites experts have moved on; it seems he is far more comfortable with metal than epoxy.
     

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