Dragon wings are hitting my torque tube, why?

[N447MR]

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

 

[gyrojake]

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.

 

[gyrojake]

Plus the bolts in your towers to the bearing block are in backwards.
You want the heads in the direction of rotation.

 

[JEFF TIPTON]

No Title

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.

 

[gyrojake]

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.

 

[twistair]

No Title

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,

 

[Paul C]

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.

 

[Gyro28866]

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.

 

[N447MR]

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

 

[Kevin_Richey]

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.

 

[twistair]

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.

 

[N447MR]

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.

 

[Doug Riley]

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.

 

[N447MR]

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?

 

[Gyro28866]

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.

 

[Vance]

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.

The teeter stops on The Predator don’t move and limit teeter movement to 18 degrees total.

It appears to me the teeter stops on G R’s head don’t move either.

I do not have a strategy for slowing the blades other than putting on the rotor brake below 100 rotor rpm. I work to keep the rotor tilt even left to right to avoid low speed blade divergence and excess control input pressure.

 

[N447MR]

Since I apparently have a modified Air Command Rotor Head, Can someone tell me if a regular AC rotorhead has separate STOPs pieces on it, or does the design of the head naturally stop the blades at the proper degreed angle?
Likewise for the Dragon Wings- does the dragon wing head have built in stops or is the simple construction of the head enough to limit it?
Thanks for any help.
Geoff

 

[gyrojake]

Since I apparently have a modified Air Command Rotor Head, Can someone tell me if a regular AC rotorhead has separate STOPs pieces on it, or does the design of the head naturally stop the blades at the proper degreed angle?
Likewise for the Dragon Wings- does the dragon wing head have built in stops or is the simple construction of the head enough to limit it?
Thanks for any help.
Geoff

Both heads in stock condition only have aluminum stop plates like the head you have.
Your towers are too long.
As quoted before, you need a stock dual bearing rotor head from RFD or Air command.
Air Command is back in business and is your best bet for the product you need.
Call RFD, he may have a head to sell you also.

 

[gyrojake]

The teeter stops on The Predator don’t move and limit teeter movement to 18 degrees total.

It appears to me the teeter stops on G R’s head don’t move either.

I do not have a strategy for slowing the blades other than putting on the rotor brake below 100 rotor rpm. I work to keep the rotor tilt even left to right to avoid low speed blade divergence and excess control input pressure.

The teeter stops Dave uses are designed for parking or to taxi without the blades spinning.
They are bolted to the top of the towers and stop the blades from flapping in the wind, they are disengaged by the centrifugal force delivered by rotation for normal flight.

 

[twistair]

Likewise for the Dragon Wings- does the dragon wing head have built in stops or is the simple construction of the head enough to limit it?

RFD rotorhead for bigger rotors (two main bearings) has centrifugal teeter stops but me personally remove them since I found that they make taxiing with slow rotating rotor too uncomfortable though such teeter stops are very useful for, say, heavy 30' SportRotors. In my personal experience teeter stop plate below a hubbar is quite enough a DW rotors.