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ENGINE PLACEMENT and THRUSTLINE

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  • ENGINE PLACEMENT and THRUSTLINE

    Start with a typical pusher gyroplane with a fixed prop position, fore/aft placement and height of thrust line. No changes to the airframe nor head placement allowed. You have two options: the engine can be placed with its COM (A) at or near the prop thrustline, or (B) 3 inches below the prop thrustline.
    Q: 1. Does it make a difference? 2. If yes, which installation is best? 3. Why?

    Thanks, looking forward to your responses! I already know the answer, just wondering what the responses will be. Hopefully some experts will take the time to chime, too!
    Last edited by NoWingsAttached; 08-10-2018, 04:46 PM.
    GT Mills
    Peachstate Rotorcraft Club

    Mohawk Aero Corporation
    PO Box 30133
    Savannah, GA 31410
    www.MohawkAeroCraft.com info@MohawkAeroCraft.com

  • #2
    Which are you asking about, the "engine's COM" as it says above, or the aircraft's COM ?

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    • #3
      Sure... everyone likes answering "gotcha" questions...

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      • #4
        You didn't mention the aircraft's current center of gravity. Engine placement affects that.

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        • #5
          Come on guys, this is elementary.
          It would be A, at or near the ENGINES COM.
          It is better to have your G/G equal or above the thrust line.
          Putting your engine C/G under the thrust line makes for a High thrust line, compared to your overall CG.
          Now I would have said Center of Gravity instead of center of mass because they change with effect of gravity and we ain't space ships !!
          If this is an Air Command installation with a Yamaha engine, it wouldn't matter, It's a Piece-O-Sh!t to start with !!!!
          Greg, if you smoke the good weed and stay off the booze you would have actually known the answer :)
          Brian Jackson
          He did give specifics that the THRUST line won't change and all else stays stationary in the new engine installation.
          Life,The leading cause of Death

          Live and Learn--OR--Die and be an example

          321.252.7705

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          • #6
            Jake, the thrust line is whichever direction the propeller is pointed, and I'm told that isn't moving. Only the CG of the engine. But I would have no way of discerning which is the best placement of that weight because he didn't tell me if the ship was CLT or not to begin with. Did I miss something?

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            • #7
              Originally posted by Brian Jackson View Post
              Jake, the thrust line is whichever direction the propeller is pointed, and I'm told that isn't moving. Only the CG of the engine. But I would have no way of discerning which is the best placement of that weight because he didn't tell me if the ship was CLT or not to begin with. Did I miss something?
              The existing C/G doesn't matter, he's installing without modifications or concerns. That's the problem with the ; That's close enough engineering.
              He was only interested of the engines C/G compared to the stationary prop thrust line.
              The machine may or may not be CLT, but that was not the concern.
              It's better LTL than HTL, and CLT is optimum, so I will alway go with weight equal or higher than thrust line.
              Plus, ya just gotta know Greg to appreciate his madness LOL !!
              Life,The leading cause of Death

              Live and Learn--OR--Die and be an example

              321.252.7705

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              • #8
                That's kind of where my thinking was leading as well, but trying to avoid that gotcha moment Tyler mentioned earlier.

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                • #9
                  Isn't this just a redrive vertical offset from engine COG question? It's not a variable that 99.9% of us can control.

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                  • #10
                    Originally posted by HighAltitude View Post
                    Isn't this just a redrive vertical offset from engine COG question? It's not a variable that 99.9% of us can control.
                    All it takes is a 7/16 wrench and a tube of caulk to flip the gear box. Pretty easy task.
                    The feel of his statement leads me to new motor mounts for either application.
                    Now modifying the machine takes some skills, but still can be done by the average gyro owner with minimal mechanical knowledge.
                    Crap, I build em from scratch and I'm retarded compared to most of you guys.
                    Life,The leading cause of Death

                    Live and Learn--OR--Die and be an example

                    321.252.7705

                    Comment


                    • #11
                      Come on Jake, retarded? this is 2018!!!, your mentally challenged, I think you need some of my hybrid tomatoes, I got 4 or 5 varieties, I'm sure one of them would give you more insight into bent and broken rotor blades.
                      Jay Gunderson

                      "Wise men talk because they have something to say;
                      fools talk because they have to say something."

                      Plato

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                      • #12
                        Can you easily change the redrive offset on a yamaha engine? All along I have assumed that the OP was referring to the Yamaha since that is his expertise.

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                        • #13
                          Originally posted by j bird View Post
                          Come on Jake, retarded? this is 2018!!!, your mentally challenged, I think you need some of my hybrid tomatoes, I got 4 or 5 varieties, I'm sure one of them would give you more insight into bent and broken rotor blades.
                          Yes Please !!
                          Yeah, I'm pretty ignorant but that's who I am, and so appreciate the fact that you accept me for who I am. Thank you Brother !!
                          So mail the mayters so I could be,............... what were we talkin about
                          Life,The leading cause of Death

                          Live and Learn--OR--Die and be an example

                          321.252.7705

                          Comment


                          • #14
                            Originally posted by HighAltitude View Post
                            Can you easily change the redrive offset on a yamaha engine? All along I have assumed that the OP was referring to the Yamaha since that is his expertise.
                            Nope. the gear box is on an offset and has to be set up with adapter to change positions.
                            What does OP mean, Original Post?
                            Life,The leading cause of Death

                            Live and Learn--OR--Die and be an example

                            321.252.7705

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                            • #15
                              original poster

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