Dragon wings are hitting my torque tube, why?

N447MR

Junior Member
gyrojake;n1133891 said:
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.
I've seen those on the sportcoper setup in our hangar, I was wondering if there was a "teeter stop" on the bottom side. Something for the blades to hit that wasn't aluminum as it looked like maybe there was something attached to mine at some point.

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. So it seems the towers were made appropriately, although it is clear the blades aren't tracking so on to learning how to do that to dragon wings.

I didn't get a lot of time to play with it after that, but it seemed to handle a little "tighter" as well. Looking forward to playing some more.

I'll have to contemplate the dual vs. single bearing head debate (which I've read extensively so far)
Ernie got back to me and said he could make me a dual bearing head for $1500. I haven't talked to AirCommand about it.
 

eddie

RAF, turbo subaru 230hp
I don't see where the double bearing rotor head is of any benefit,I have a single bearing head on my RAF with no problems.
 

gyrojake

Gyro Rehab Candidate
eddie;n1133903 said:
I don't see where the double bearing rotor head is of any benefit,I have a single bearing head on my RAF with no problems.
Eddi,
It is because of the oscillations of the radial load, the axial load is no problem but with big heavy loads the radial load is compensated with the dual bearing stack.
These bearings are designed for axial thrust loads. Better safe than sorry, I know your worth another couple -o-bucks for safety redundancy.
 

N447MR

Junior Member
gyrojake;n1133904 said:
Eddi,
It is because of the oscillations of the radial load, the axial load is no problem but with big heavy loads the radial load is compensated with the dual bearing stack.
These bearings are designed for axial thrust loads. Better safe than sorry, I know your worth another couple -o-bucks for safety redundancy.
In all the reading though, just one accident involving suspect rotor head bearings on a J2 that was stored outside and displayed significant issues/warnings that should have been addressed before it failed.
 

Gyro28866

David McCutchen
With the block now in the top hole, the teeter is as it should be. So it seems the towers were made appropriately, although it is clear the blades aren't tracking so on to learning how to do that to dragon wings.
I will attempt to explain this in a manner for you to also visualize.
On the Dragonwings, the only adjustment for the end user is just to adjust for lead/lag. Place the rotor onto 2 saw horses, several feet from where the blade attaches to the hubbar. One sawhorse for each blade. you will adjust the sawhorses closer or farther out, attempting to get the hubbar into a slightly lower position than the rotor blade tips. You will attach a string and pulled tight to the tip of each blade, I use the seam where the upper skin is attached. This position is exactly the same on each blade. With the string pulled tightly across, the hubbar teeter block should be slightly below the string. roughly 1/4" to 1/2". If the teeter block is touching the string, then adjust each of the two sawhorses out the same amount, until the string is not touching. The string should be crossing the teeter block at the dead center mark.
Also, because Ernies blades have a length wise twist. You have to compensate for that also. Cut you 2 pieces of automotive fuel line about two inches long each. These pieces will be inserted between the saw horse and the rotor blade. They MUST be inserted parallel the blades cordline, approx. 1 3/4" from the leading edge. this will get the blades into a position which closely resembles flying attitude. loosen the grip of the 6 blade bolts, on each blade strap. and adjust the lead/lag until you get it right.
This all sounds complicated, but it really is not. real easy, once you have done it.
Meet me at Mentone, and I will be glade to show you.
 

eddie

RAF, turbo subaru 230hp
Another way to adjust the lead/lag is to slightly loosen the bolts on the blades and then run up the blades to a speed where the blades are carrying

a load and then slow down and let the blade stop without the brake or any assistance,after they have stopped tighten the bolts,taxi back to the hanger

and torque the bolts down. the blades adjusted this way will find its own lead/lag.

Jake with the blades teetering where does the radial load come from ?
 

gyrojake

Gyro Rehab Candidate
eddie;n1133908 said:
Jake with the blades teetering where does the radial load come from ?
When your rotor is spinning under load, the drag of the rotor loads and unloads radial forces on the bearing.
The teeter takes care of the dissymmetry of lift not radial loads.
My best analog would be to stand in the back of a pick up truck at 60 miles per hour.
Hold a piece of 2'x2' plywood edgewise in the wind then the flat surface in the wind at 300 times a minute and you will then notice the radial oscillations your mast and bearings are withstanding.
I'm sure C.B. can explain it better.
The more support you give to the length of the bearing surface the more you displace the radial load and consequently displace the axial load with dual bearings, which means your bearings are taking less of a beating.
Anything over 750lbs in my opinion should have 2 bearings.
 
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N447MR

Junior Member
gyrojake;n1133910 said:
When your rotor is spinning under load, the drag of the rotor loads and unloads radial forces on the bearing.
The teeter takes care of the dissymmetry of lift not radial loads.
My best analog would be to stand in the back of a pick up truck at 60 miles per hour.
Hold a piece of 2'x2' plywood edgewise in the wind then the flat surface in the wind at 300 times a minute and you will then notice the radial oscillations your mast and bearings are withstanding.
I'm sure C.B. can explain it better.
The more support you give to the length of the bearing surface the more you displace the radial load and consequently displace the axial load with dual bearings, which means your bearings are taking less of a beating.
Anything over 750lbs in my opinion should have 2 bearings.
So is that kind of like a shear force on the bearings?
also, is that 750#s all up or empty machine?
thanks for the patience in exposing and teaching.
Geoff
 

gyrojake

Gyro Rehab Candidate
No Title

N447MR;n1133914 said:
So is that kind of like a shear force on the bearings?
also, is that 750#s all up or empty machine?
thanks for the patience in exposing and teaching.
Geoff
Wet and passengers.
Here look at this.
Remember, axial is thrust and radial is a bending moment 90* of the thrust.
 

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gyrojake

Gyro Rehab Candidate
You also have to look at the wear and tear of a single bearing in the ALUMINUM bearing block.
Think of a lever pulling back and forth on the bearing.
Two bearings have more surface than one and can withstand higher radial loads.
 

N447MR

Junior Member
Gyro28866;n1133906 said:
I will attempt to explain this in a manner for you to also visualize.
On the Dragonwings, the only adjustment for the end user is just to adjust for lead/lag. Place the rotor onto 2 saw horses, several feet from where the blade attaches to the hubbar. One sawhorse for each blade. you will adjust the sawhorses closer or farther out, attempting to get the hubbar into a slightly lower position than the rotor blade tips. You will attach a string and pulled tight to the tip of each blade, I use the seam where the upper skin is attached. This position is exactly the same on each blade. With the string pulled
This all sounds complicated, but it really is not. real easy, once you have done it.
Meet me at Mentone, and I will be glade to show you.
I hope to Fly into Mentone this year and look forward to the meeting.
This is “stringing” though and not tracking, right?
I did string the blades when I put them together, but I was unaware of this fuel line trick. At some point I did try and sling them also, but noticed no difference. Some speculated that the stringing was pointless claiming that the centrifugal forces were so strong that no matter how tight the bolts were the blades would essentially “sling” themselves anyway. Anyone have thoughts on that?
 

gyromike

Administrator
Staff member
If you have already strung your blades, and they are still out of track, lift them out of the teeter towers and spin the head 180º and put them back on to see if that make a difference.
If that doesn't get them in track, it's time for shims.

To track a set of Dragon Wings, you would need to use shims between the teeter block and the hub bar, but only on one side.
You just have to loosen the two vertical bolts in the teeter block enough to slip a shim under it, then re-tighten. I don't recall the torque specs right off the top of my head though.

I used shims made from Coke cans (~0.003" to 0.004" thickness).
It's kind of a hit and miss process unless you can identify which blade is flying high, or low.
Adding a shim under one side of the block adds pitch to one blade while removing pitch from the other.

I just put a shim under one side, and if it tracked worse I took it out and put it under the other side and kept adding until they tracked together.
Then I marked the hub bar and rotorhead so that if I took the blades off, I always put them back on the same way.
 

N447MR

Junior Member
gyromike;n1133933 said:
If you have already strung your blades, and they are still out of track, lift them out of the teeter towers and spin the head 180º and put them back on to see if that make a difference.
If that doesn't get them in track, it's time for shim

I just put a shim under one side, and if it tracked worse I took it out and put it under the other side and kept adding until they tracked together.
Then I marked the hub bar and rotorhead so that if I took the blades off, I always put them back on the same way.
Awesome, thank you. Can you really tell a definite difference in just one thin shim?
I just landed from flipping the towers 180*. I should mention previous owner had the towers and teeter marked R.H & L.H. But out of diligence I did it anyway just to see. The stick felt about the same but I could notice my leg and instrument pod bouncing more. So now I’ll put it back and start with the shims.
 
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gyromike

Administrator
Staff member
N447MR;n1133950 said:
Can you really tell a definite difference in just one thin shim?
It just depends on how far out the blades are.
Just pick a side and start shimming.

For some reason the tracking of the tips was more noticable when I was in a bank with the clouds in the back ground.
 

N447MR

Junior Member
No Title

gyromike;n1133952 said:
It just depends on how far out the blades are.
Just pick a side and start shimming.

For some reason the tracking of the tips was more noticable when I was in a bank with the clouds in the back ground.
Make sense. How many shims would you expect to use; 2,3.5? I know it probably depends, but I'm thinking if you put 5 in there and there's no difference, then it's probably not going to, right?

And as for the size of the shim; I read earlier, but I don't see any in my teeter block at all as they sit now. They would have to begin at the edge, and run the length of the block, but would they go all the way to the halfway of the width? And you're putting a hole in it for the bolt to go through, yes?
I drew this rudimentary picture with the red being the outline of the shim.
 

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Vance

Gyroplane CFI
I would start using one shim at a time so you can feel the change. Using five you may go past the ideal setting.
 

N447MR

Junior Member
Vance;n1133981 said:
I would start using one shim at a time so you can feel the change. Using five you may go past the ideal setting.
Yes, agreed. I more meant that if I get to 5 without improvement then that’s the wrong direction.
Any thought on my crude drawing?
 

eddie

RAF, turbo subaru 230hp
One of the best things to use is buy a feeler gauge and use the gauges for the shims,I would only go about 0.002 at a time 0.005

will probably move the tips about 1/2 ",remember as one tip go's up the other side go's down.
 

N447MR

Junior Member
eddie;n1133989 said:
One of the best things to use is buy a feeler gauge and use the gauges for the shims,I would only go about 0.002 at a time 0.005

will probably move the tips about 1/2 ",remember as one tip go's up the other side go's down.
Do you find any made of aluminum to eliminate rust potential? Also, those feeler gauges seem to be much thinner with a 0.5" width than what I put in that drawing, so I guess it doesn't have to have the bolt through it.
 
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