Raptor Composite Aircraft

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

Help Support HomeBuiltAirplanes Forum by donating:

  1. Oct 19, 2019 #2221

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,032
    Likes Received:
    2,346
    Location:
    Port Townsend WA
    Does belt jumping indicate he is getting more power now? ;)
    Maybe he needs a third belt.
     
    BoKu likes this.
  2. Oct 19, 2019 #2222

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,854
    Likes Received:
    1,843
    Location:
    North Carolina
    He has a fixed idler. His engine moves relative to the output shaft. Belt tension is going to vary as the engine moves.
    He needs the engine and output shafts to be a fixed distance apart. With variable tension, the drive is doomed. Tooth jumping puts immense strain on belts. Even having them poorly tensioned puts huge strain on them as they will not mesh properly and will ride up the teeth. Too much tension is also bad, overly straining the belt. Has nobody read the story of Goldilocks and the three bears?
    A sprung idler might help, but if the shafts are not staying parallel because of the non rigid shaft arrangement, it will only delay the inevitable failure.
     
    cheapracer, akwrencher and BoKu like this.
  3. Oct 19, 2019 #2223

    cheapracer

    cheapracer

    cheapracer

    Well-Known Member

    Joined:
    Sep 8, 2013
    Messages:
    5,318
    Likes Received:
    3,570
    Location:
    Australian

    What can be said other than what I said a few posts ago, only a moron would mount the engine on flexible mounts, a diesel at that, and the belt driven PSRU on a seperate, solid mount.
     
    bmcj and BoKu like this.
  4. Oct 19, 2019 #2224

    flywheel1935

    flywheel1935

    flywheel1935

    Well-Known Member

    Joined:
    Nov 1, 2018
    Messages:
    99
    Likes Received:
    41
    Location:
    Downham Market, Norfolk, UK.
    Having just retired from 50 years of engineering Rocket Motors, Light & Microlight Aircraft and Le Mans Porsches, I now despair at the arrogance of
    a 'non-engineer' who wants to sell to Joe-Public a totally flawed concept, whats wrong with a Velocity ?????
     
    PagoBay likes this.
  5. Oct 19, 2019 #2225

    Doggzilla

    Doggzilla

    Doggzilla

    Well-Known Member HBA Supporter

    Joined:
    Jun 2, 2013
    Messages:
    1,888
    Likes Received:
    396
    Location:
    Everywhere USA
    Interesting. I know motorcycles run like that. What is the solution they use?

    The belts have far more movement than this. What solution do they use?
     
    flywheel1935 likes this.
  6. Oct 19, 2019 #2226

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,032
    Likes Received:
    2,346
    Location:
    Port Townsend WA
    Looks like the estimated production empty weight has been increased to 2300 pounds (from 1800, I think it was)
    This only makes sense, as I suggested in previous posts, since it can't be lighter than other pressurized aircraft in this class.
    The prototype remains some 700 or more overweight.
     
  7. Oct 19, 2019 #2227

    flywheel1935

    flywheel1935

    flywheel1935

    Well-Known Member

    Joined:
    Nov 1, 2018
    Messages:
    99
    Likes Received:
    41
    Location:
    Downham Market, Norfolk, UK.
    On a m/bike, like a Harley, the cog for the gearbox drive will be on the pivot line of the swing-arm, so it makes no difference to the belt length
    as the suspension goes up and down, it stays at constant length, the major design flaw with the ' Craptor' is the engine can move on its mounts but the Prop drive cant,
    so the belt never run true to the toothed cogs, and if a bike belt fails you just pull over !!!!
     
  8. Oct 19, 2019 #2228

    Doggzilla

    Doggzilla

    Doggzilla

    Well-Known Member HBA Supporter

    Joined:
    Jun 2, 2013
    Messages:
    1,888
    Likes Received:
    396
    Location:
    Everywhere USA
    That makes sense.

    The only way he’s going to get that with this setup would be to switch to flexible mounts for the PSRU and run a sub frame between the two so that the PSRU can flex with the engine.
     
  9. Oct 19, 2019 #2229

    flywheel1935

    flywheel1935

    flywheel1935

    Well-Known Member

    Joined:
    Nov 1, 2018
    Messages:
    99
    Likes Received:
    41
    Location:
    Downham Market, Norfolk, UK.
    Sorry Doggzilla, you've got it all wrong, Both the engine and prop-drive need to be integrated in one unit, then that whole unit need to be hung off a 'Dynofocal' type engine mount.
    ps. is your dog a Husky ? mines a Cockapoo :)
     
    wsimpso1 likes this.
  10. Oct 19, 2019 #2230

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    649
    Likes Received:
    154
    Location:
    Just an Ohioan
    So in the latest video at 21:20 and 27:40 you can see the plane vibrate and smoke in the exhaust. Motec is telling him that there is a mechanical problem. I don't think he is aware of the smoke.
     
  11. Oct 19, 2019 #2231

    Doggzilla

    Doggzilla

    Doggzilla

    Well-Known Member HBA Supporter

    Joined:
    Jun 2, 2013
    Messages:
    1,888
    Likes Received:
    396
    Location:
    Everywhere USA
    What did he do about the intercooler airflow issue? Havent bothered watching. Too long.
     
  12. Oct 20, 2019 #2232

    Doggzilla

    Doggzilla

    Doggzilla

    Well-Known Member HBA Supporter

    Joined:
    Jun 2, 2013
    Messages:
    1,888
    Likes Received:
    396
    Location:
    Everywhere USA
    The problem is that hes already chosen this layout, so hes got to work with what he has.

    And its not actually my Dog, I used to volunteer at the Humane Society.
     
  13. Oct 20, 2019 #2233

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    649
    Likes Received:
    154
    Location:
    Just an Ohioan
    I don't think he has done anything. If not then he is dealing with 450+°F temps and is heat soaking the intercooler. Which means he has lost half of the density/mass so the engine is starved for air but still shows 40+ psi since it is still moving volume. Interesting that it tends to happen on the later runs of each session. If he doesn't have a lot of fuel onboard it will be worse.
    Screenshot_2019-10-19-22-07-46.png
    Edit: Would that lead to compressor stall(surge)??? That would explain the vibrations.
     
  14. Oct 20, 2019 #2234

    christos

    christos

    christos

    Well-Known Member

    Joined:
    Nov 9, 2018
    Messages:
    50
    Likes Received:
    12
    Location:
    Greece
    We need the compressor map, airflow and pressure to check if turbo surge.
     
  15. Oct 20, 2019 #2235

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,854
    Likes Received:
    1,843
    Location:
    North Carolina
    Low pressure turbo is a 2867, high pressure turbo is a 2871. Yes, really. We can pick some numbers out of his data shots and estimate VE to get airflow and find that the low pressure turbo is well into choke. Surge would need much bigger turbos than optimum. He has way smaller turbos than he needs.
     
  16. Oct 20, 2019 #2236

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,854
    Likes Received:
    1,843
    Location:
    North Carolina
    Too cramped, no AC, not pressurised, inefficient, poor range. Won't make Peter rich.
    Most importantly, no cupholders!
     
  17. Oct 20, 2019 #2237

    Scheny

    Scheny

    Scheny

    Well-Known Member

    Joined:
    Feb 26, 2019
    Messages:
    141
    Likes Received:
    64
    Location:
    Vienna, Austria
    This is not true, if you go back two pages I exactly wrote about the cycles just don't care as it is a very small part of their lifetime... It should be equidistant, but not all are doing it.
     
    flywheel1935 likes this.
  18. Oct 20, 2019 #2238

    christos

    christos

    christos

    Well-Known Member

    Joined:
    Nov 9, 2018
    Messages:
    50
    Likes Received:
    12
    Location:
    Greece
    Did you mean gtx2867? Is it peter's turbo?

    # it is high pressure if you read compressor map.

    What type of exhaust house does it use?
     
  19. Oct 20, 2019 #2239

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,032
    Likes Received:
    2,346
    Location:
    Port Townsend WA
    It looks to me the prop is a significant mass hanging off the back of a steel tube truss holder that can pivot up down, because not attached to engine. (as others noted)
    So the prop weight would keep the belt tight in static tests, but bounce up and down hitting bumps on the runway.
    When the prop bounces upward the forward belt would get loose.
    I heard him say "Mark" designed the PSRU. (video of PSRU assembly)
     
  20. Oct 20, 2019 #2240

    poormansairforce

    poormansairforce

    poormansairforce

    Well-Known Member

    Joined:
    Mar 28, 2017
    Messages:
    649
    Likes Received:
    154
    Location:
    Just an Ohioan
    Thats what I thought also but is that accounting for density/mass loss at high temps?
     

Share This Page

arrow_white