Dragon wings are hitting my torque tube, why?

gyromike

Administrator
Staff member
I think I made mine about 3/4" wide and as long as the side of the block, and punched a hole for the bolt.

You will start noticing a difference from the first shim.
Stick a shim under one side and it will either get better or worse.
If it gets worse, move it to the other side and keep adding until the blades tips are in track.
I kept adding shims until it went out of track again slightly, then removed shims until it was back in track.
 

Gyro28866

David McCutchen
Hello Geoff:
Let me see if I can explain this in a way that makes sense and you can visualize.
The teeter bolt and Bushings/Majic hats and Teeter block are a rigid/solid component. If machined correctly, there will be several thousands clearance.; as much as 20 thousands clearance to the Teeter Towers. This will allow the teeter block and hub bar to move side to side within the tower. Between the bushings and tower there is a plastic washer inserted. The aluminum SHIMS are placed between the plastic washer/shim and bushing top. You are shimming to close the gap to 4 to 8 thousands total. You should be able to take a flathead screwdriver and move the teeter block back and forth between the towers and have a total of only 4 to 8 thousands play. And you are trying to get it shimmed to the exact rotational center.
If you shim out all the gap/play and the teeter block and tower are being pushed together, you will have a pronounced stick shake (two per rev vibration) and probable galling and heat buildup at the tower and bushing area.
Hope this helps and hope to see you at Mentone.
Start making a list of questions to ask while you are there.
 

N447MR

Junior Member
gyromike;n1134018 said:
I think I made mine about 3/4" wide and as long as the side of the block, and punched a hole for the bolt.

You will start noticing a difference from the first shim.
Stick a shim under one side and it will either get better or worse.
If it gets worse, move it to the other side and keep adding until the blades tips are in track.
I kept adding shims until it went out of track again slightly, then removed shims until it was back in track.

Perfect, I'll give it a try and report back. I thought I read someone saying they just loosened the teeter tower bolts and slipped shims in. Also, as note for future readers, Mr. Boyette emailed me back and told me that there are no torque specs of any consequence for the teeter block bolts that hold the tower to the hub. Just tighten it up real well.
 

N447MR

Junior Member
No Title

Gyro28866;n1134039 said:
Hello Geoff:
Between the bushings and tower there is a plastic washer inserted. The aluminum SHIMS are placed between the plastic washer/shim and bushing top. You are shimming to close the gap to 4 to 8 thousands total.
If you shim out all the gap/play and the teeter block and tower are being pushed together, you will have a pronounced stick shake (two per rev vibration) and probable galling and heat buildup at the tower and bushing area.
I took the rotors off a couple days ago to check balance (seem pretty darn good still) and everything looks good to me visually. I didn't notice any plastic washers. There's no galling or apparent heat build up or wear. The only washers are on the outside of the teeter towers between the bolt head and on the other side between the nut and tower. I attached another crude drawing.
Should the plastic washer you reference be on the inside of the teeter tower?
Does the plastic washer contact the teeter block, or is it between the bushing and the teeter tower somehow?

I numbered the options I tried to explain the second drawing, but I don't know if it is clear.
 

Attachments

AirCommandPilot

Just a fledgeling
The teeter bolt, teeter block, and hat bushing should all move as one piece. That block assy should move together back and forth within the tower with the 4-8 thousands tolerance.
 

N447MR

Junior Member
N447MR;n1134110 said:
Perfect, I'll give it a try and report back. I thought I read someone saying they just loosened the teeter tower bolts and slipped shims in. Also, as note for future readers, Mr. Boyette emailed me back and told me that there are no torque specs of any consequence for the teeter block bolts that hold the tower to the hub. Just tighten it up real well.
Put ONE shim under the Right side of the teeter block and hub bar and didn't notice anything I could be sure about. Put a second shim in the Right side and at first didn't seem to notice much, but then realized over 50-60 mph indicated it felt really bumpy on the stick. Looking at the blades there was still definite separation (two lines).

Took both shims out of the Right side and installed BOTH (two shims) on the Left side. Definitely noticed a smoothing and certainly was nicer over 60mph. Fairly certain that the separation of the two blades was less too. It was a nice night so I just flew around for 45 minutes at that point.

After putting the Gyro away, I took One shim OUT so there is now ONE shim in the left side instead of two. I will see how that feels next time and either go to three or leave it. I'll let you know!

How many shims would you all think it would normally take? How many is too many?
 
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Gyro28866

David McCutchen
The shims are placed where in the drawing you have the washer.
NOTHING goes where you have 1 and 2 indicated.
 

N447MR

Junior Member
Gyro28866;n1134386 said:
The shims are placed where in the drawing you have the washer.
NOTHING goes where you have 1 and 2 indicated.
Thanks for getting back. Between the washer and the hat then. Are they put on both sides equally?
 

Gyro28866

David McCutchen
Thanks for getting back. Between the washer and the hat then. Are they put on both sides equally?
Normally , YES.
However, if you have a heavy blade and the the rotor is following it, the stick will move in a circular motion; and you are shimming to migrate the rotating mass to center.
 

N447MR

Junior Member
N447MR;n1134381 said:
Put ONE shim under the Right side of the teeter block and hub bar and didn't notice anything I could be sure about. Put a second shim in the Right side and at first didn't seem to notice much, but then realized over 50-60 mph indicated it felt really bumpy on the stick. Looking at the blades there was still definite separation (two lines).

Took both shims out of the Right side and installed BOTH (two shims) on the Left side. Definitely noticed a smoothing and certainly was nicer over 60mph. Fairly certain that the separation of the two blades was less too. It was a nice night so I just flew around for 45 minutes at that point.

After putting the Gyro away, I took One shim OUT so there is now ONE shim in the left side instead of two. I will see how that feels next time and either go to three or leave it. I'll let you know!

How many shims would you all think it would normally take? How many is too many?
Flew it with ONE shim on the Left side, where I left off, and I couldn't say it was any better, maybe a bit worse? Then I added two back to have a total of THREE on the left side. I feel like it had a strange feel to it, and was probably a bit worse, but I couldn't pin point it. So I put a FOURTH one in there and put it away. Hopefully I'll fly it tomorrow. Four seems like a lot looking at it. We'll see.
 

N447MR

Junior Member
N447MR;n1134475 said:
Flew it with ONE shim on the Left side, where I left off, and I couldn't say it was any better, maybe a bit worse? Then I added two back to have a total of THREE on the left side. I feel like it had a strange feel to it, and was probably a bit worse, but I couldn't pin point it. So I put a FOURTH one in there and put it away. Hopefully I'll fly it tomorrow. Four seems like a lot looking at it. We'll see.
Flew it with ONE shim on the Left side, where I left off, and I couldn't say it was any better, maybe a bit worse? Then I added two back to have a total of THREE on the left side. I feel like it had a strange feel to it, and was probably a bit worse, but I couldn't pin point it. So I put a FOURTH one in there and put it away. Hopefully I'll fly it tomorrow. Four seems like a lot looking at it. We'll see.

Flew it with FOUR shims expecting obviously worsening condition, but didn't. Was kind of indecisive really.
Went back down to TWO shims expecting it to be obviously smoother, but is wasn't. Probably better than when I started...I think maybe; but I wouldn't bet much on it.
So, I gave up. Four shims was visually alot. I figured if there wasn't a change there then FIVE was just being silly. YES, NO?

Took some video today using the SLO MO on the iphone. Kinda worked out. I may make a new thread sumamrizing all your input just to make anyone searching this topic again easier.
Video link here.
https://youtu.be/U64oam8WTS0
 

eddie

RAF, turbo subaru 230hp
looks like it might benefit from making sure the blades are centered between the towers.

A few thousands will make a lot of difference.
 

N447MR

Junior Member
Gyro28866;n1134403 said:
Normally , YES.
However, if you have a heavy blade and the the rotor is following it, the stick will move in a circular motion; and you are shimming to migrate the rotating mass to center.
I think I get the centering idea. The hat bearing moves in and out of the tower a tad so when it’s all tightened up it can move as much as that.
I found a when I took the rotors off this time I found extra play in the left side bearing. The measurements of the hole in the tower seem off. 0.75” side to side 0.78” up and down. I took a video. What do you think?
 

Gyro28866

David McCutchen
I did not like what I saw. I am thinking this is not a RFD machined tower. Ernies towers have a roller bearing in them and the bushings are teetering in the roller bearings. If yours are just bushing to tower and they have wore the slop into it. That is likely the culprit for the odd stick shake. Instead of just flapping/teetering on a fixed position, it is also able to move out of center; and is flapping on a moving out of center position.
I am no expert, by any stretch. But my gut feeling is excessive wear in bushings and towers.
 
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