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Dragon wings are hitting my torque tube, why?

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  • Dragon wings are hitting my torque tube, why?

    UPDATE below.
    Okay- So I finally got back to the airport yesterday and to my surprise, the teeter block was NOT in the top hole. This really surprised me because I thought that it had been there all along and so hadn't considered it further. Always humbling. None of the guys at the hangar thought of it in all this time either. I'm very grateful to have the additional online forum help, thank you.

    With the block now in the top hole, the teeter is as it should be.



    CLT Tandem Air Command, Subaru 2.2, Warp drive prop, 28or 29' dragon wings, electric prerotator. I've got over 100 hours on this machine. Sure does fly nice as best I can tell. More stick shake than I'd like since flying my friends MTO, but perhaps its as good as it gets.
    Problem is, if there's any kind of wind that gets under the rotor before or as I'm spinning them up, they can be at such an angle that the hub will hit the torque tube on the mast. Until I'm up over 50 rpm or so it can do this and it hits it enough to be really un-fun and it can stop the blades. It will even be on an extreme enough angle that it can scrape the ground if I'm taxiing out and don't have the rope on it. It doesn't matter if I have the stick forward or not because it is teetering so that it doesn't matter the angle of the whole head. I've attached pictures that I took in the hangar where you can see there where it can hit the tube. (though it would hit the other side when spinning, it was just to take a pic). some have suggested I need a rubber stop of some kind under the teeter block to act as a stop, but I don't know what that does when I need the stick forward, I don't know how the "teetering" looks when spinning at flight speeds.
    As it is now, I taxie down close to the end of the runway and pull the blades down with the tie rope so I can get hold of them. Then I give them a good heave-ho and try to engage the prerotator ASAP so they spin up before any wind can cause them to teeter too much. This has happened only a few times, but I don't like it and when I go out to have fun on a windy day it concerns me cause it can hit hard, then I have to go back and make sure nothing is messed up(and it hasn't been yet other than a couple small gouges out of the hub corner).

    Tried to be clear, but please let me know if I can be more clear. Just want to find out if this is either something to live with, fix, or could be dangerous beyond what I've already explained.

    Thank you very much for the help.

    Geoff
    Attached Files
    Last edited by N447MR; 05-26-2018, 06:10 AM. Reason: updated to include the answer found later in the discussion
    Air Command CLT Tandem
    BROKE, SIEZED, NO GOOD, Subaru 2.2 FI- Stock
    68" Warp Drive
    28' Dragon Wings
    0 #'s Thrust

  • #2
    Looks like you have to much swing in your teeter.
    You only needs 3/4" total swing.
    You need to make some plastic blocks that you can bolt to your stop plates .
    When level you need about 3/8" from stop to hub bar and when all the way against the stop you will have 3/4" between the stop and hub bar.
    Life,The leading cause of Death

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

    321.252.7705

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    • #3
      Plus the bolts in your towers to the bearing block are in backwards.
      You want the heads in the direction of rotation.
      Life,The leading cause of Death

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

      321.252.7705

      Comment


      • #4
        Look at the upper part of the rotor tower and will notice what looks like an inverted tee. Does your head have this. It limits the rotor tilt until centrifugal force slings them out.
        PRA member 41204
        PRA Chapter 16

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        • #5
          Originally posted by JEFF TIPTON View Post
          Look at the upper part of the rotor tower and will notice what looks like an inverted tee. Does your head have this. It limits the rotor tilt until centrifugal force slings them out.
          Flap stops are an accessory not a necessity. Proper swing is a safety factor and a necessity.
          Life,The leading cause of Death

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

          321.252.7705

          Comment


          • #6
            Click image for larger version

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            Looking at the last photo it seems like your teeter bolt goes not through the upper hole in the hub block. Check it - if this is so then it's a reason. DW28 must hang at upper hole of the hub block (if the hub block is original then it has 4 holes).
            If it hangs at the upper hole then yu need to rearrange teetering play angle - it's obviously toooo big. This is not good and this is really dangerous for your pocket. If I were you I'd stop flying immediately until this problem is eliminated. Common rule is that teetering play angle should be within 7-8 degrees from neutral (level) to stop in each direction. In your case this can be adjusted by lengthening the teeter stop plate (this one which covers the main bearing) or either installing some teeter stop blocks (usually made of hard plastic like at the attached photo. But first check if your rotor hang at the upper hole of the hub block.

            Fly safe,
            Alex Lameko
            Russian gyroforum
            Visit my collection of gyro videos

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            • #7
              When I set my head up I had 9 degrees teeter forward and 9 degrees back. That's not stick movement angle, it's the angle of the hub when it sits on the teeter stop blocks. My rotor blades are 29' and clear the ground easily.

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              • #8
                I am going for a stab in the dark. In the last picture, it appears the Teeter bolt is passing through the second hole in the teeter bolck, instead of the top hole. Flying the rotor in this position will increase the amount of teeter and will reduce the amount of undersling. While in flight, the rotors vertical CG is above the teeter bolt and this might be the vibration/2 per rev stick shake you are experiencing.
                David McCutchen
                615-390-2228
                Bensen B7m, 90 hp Mac
                Dominator Tandem, 100 hp Hirth
                Kolb Mark III Classic, 80 hp Verner
                Certified - Advanced Master Beef Producer
                EAA Member #0511805
                PRA Member #28866
                PRA Chapter 16 Member
                Secretary & Treasure - PRA Chapter 16
                President / Sylvia - Yellow Creek Volunteer Fire Dept.
                Chairmen - Dickson County Veteran's Day Committee
                Volunteer - Dickson County Airport Aviation Day Committee
                2 busy 2 No!

                Comment


                • #9
                  Wow, so grateful for the thoughtful replies. Thank you.
                  I bought this machine from the guy who built it, so other than what's there I can't be sure if he missed something other than having airworthiness certs and an A&P sign off.

                  I don't have the flap stops, but those appear to help with the movement up rather than down. Another fella in the hangar has sportcopters, another mccutchens, and another mto so I don't have a lot to look at.

                  Thanks for the pictures Twistair, it pretty plainly shows an apparent solution, but why wouldn't something like this come with the Dragon Wings? Seems like one wouldn't sell something that required a user mod out of the box, right? But I didn't buy them, so right now I don't know. Rotor Flight Dynamics has apparently stopped production but I've reached out.

                  GyroJake, you reiterate what some of the guys told me, but with a more clear measuring guide with less ambiguity. I was afraid to limit the swing without knowing it was okay to do so.

                  Paul C and Mr. McCutchen, - I believe that it is in the top hole of the block, but I can't be sure from the couch. I will double check that today since its a beautiful day to do so. I recall learning about undersling things and thought I did what you suggest. I hope I did it wrong and its a fix without modifying things!

                  Again, thank you. If the teeter bolt is in the top of the block already and I do need to add stops, has anyone done so, and how? Should I just cut some hard plastic and bolt them to he head?

                  Gratefully,
                  Geoff


                  Air Command CLT Tandem
                  BROKE, SIEZED, NO GOOD, Subaru 2.2 FI- Stock
                  68" Warp Drive
                  28' Dragon Wings
                  0 #'s Thrust

                  Comment


                  • #10
                    No one has mentioned it, so I am wondering why the rotorblade-to-hub bar bolts are head up. I know some people feel that way if the nuts come off in flight (what chance is that to occur when using plastic-lock nuts?) then the bolt would stay in place due to gravity.

                    But with the bolt heads underneath the rotorblades and the threaded end of the bolt & nut sticking up prevents that end in a down position from hitting anything in a blade-flapping (or sailing) situation.

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                    • #11
                      This setup (bolt heads down), Kevin, is necessary for Dominators due to their upper control cross bar is long and therefore nuts on rotor may hit it. AirCommand cross bar is evidently shorter so it is likely safe with long hub bar. Sure owner should check this.
                      Alex Lameko
                      Russian gyroforum
                      Visit my collection of gyro videos

                      Comment


                      • #12
                        UPDATE: So I was able to get hold of the super nice fella I bought the machine from and he told me he had the Teeter Towers manufactured. I Also heard from Mr. Boyette who recognized that they were not of his design and that the total movement from stop to stop should be no more than 18 degrees. I was also told it is a single bearing head and I needed a double bearing head.

                        Anyone have a double bearing RFD head for 28' blades they want to sell?

                        Also, Kevin_Richey, twistair is correct that there is nothing for the bolts to hit on this machine. Either because the cross bar is shorter or the 28' rotor hub bar is longer, but if these bolts ever contact anything on this machine, it'd be the least of your concerns and a real bad day. Thank you for pointing it out though. I don't know (some of) what I don't know.
                        Air Command CLT Tandem
                        BROKE, SIEZED, NO GOOD, Subaru 2.2 FI- Stock
                        68" Warp Drive
                        28' Dragon Wings
                        0 #'s Thrust

                        Comment


                        • #13
                          In addition to keeping the blades from striking something when they flap on the ground, the teeter stops also help to limit excessively large/fast control inputs in flight. Therefore, the 18 deg. teeter range should be preserved.

                          Comment


                          • #14
                            Originally posted by Doug Riley View Post
                            In addition to keeping the blades from striking something when they flap on the ground, the teeter stops also help to limit excessively large/fast control inputs in flight. Therefore, the 18 deg. teeter range should be preserved.
                            Would the blades actually hit the stops while they are at flight speed, loaded and in flight? That seems no good if a control input can do that, no?
                            Air Command CLT Tandem
                            BROKE, SIEZED, NO GOOD, Subaru 2.2 FI- Stock
                            68" Warp Drive
                            28' Dragon Wings
                            0 #'s Thrust

                            Comment


                            • #15
                              the teeter stops also help to limit excessively large/fast control inputs in flight
                              I don't think so!!! The teeter limits are positioned horizontal while in flight. The centripetal forces from rotation do this. The only time they are hanging/drooping down is in low RRPM, to limit the amount of teeter. The only time I notice them is from about 60 to 80 RRPM, while slowing to stop the rotors rotation. It is pretty unnerving for me, when they are engaging. There is a pronounced side to side motion and corresponding stick pressure. To assist in slowing the rotor, upon landing and stopping, I turn the Dominator so the incoming wind is 90* to the machine on the advancing blade side. In higher velocity winds, I will actually turn 180* and let the incoming air feed from behind. These two maneuvers reduce the amount of flapping because of the reduction the relative wind velocities to the AOI and AOA of the rotor and blades.
                              David McCutchen
                              615-390-2228
                              Bensen B7m, 90 hp Mac
                              Dominator Tandem, 100 hp Hirth
                              Kolb Mark III Classic, 80 hp Verner
                              Certified - Advanced Master Beef Producer
                              EAA Member #0511805
                              PRA Member #28866
                              PRA Chapter 16 Member
                              Secretary & Treasure - PRA Chapter 16
                              President / Sylvia - Yellow Creek Volunteer Fire Dept.
                              Chairmen - Dickson County Veteran's Day Committee
                              Volunteer - Dickson County Airport Aviation Day Committee
                              2 busy 2 No!

                              Comment

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