Torque tube straightness and vibrations??

[ibflyen]

I am having problems finding a straight TT. My original TT was pinned on the ends and straight as an arrow as i checked it on a hi point balancer. Since then i have ordered 3 different TTs from different vendors and they are all the new ones with threaded ends on them. Im not sure if they are twisted and bent a little during assembly or what but none are straight!
At the speed that thing turns i would think having a perfectly straight TT would make a huge difference as far as vibrations go!

Bottom line is i cant find a straight one and wondered about putting in extra bearings to maybe help take the slight bend out of it.
I would really like some input from you guys on what you think the best combination of bearings and placement on the the tube would be to get the truest running TT.
I

[Helico-pteron]

A slight arc in the TT is not an issue using the two supplied bearings. The arc is removed after both ends are fitted into the drive gear sockets.

[ibflyen]

Are you assuming this is not an issue or have you done testing to eliminate this as a possible source of vibration?
For one ,the ends of the tt don't fit tight enough into the gears to totally straighten the tube and secondly the bearings are in a soft rubber which would allow movement of the tt.
The tt must be spinning roughly 6000 rpm and to have the slightest wobble would create quite a bit of vibration I would think. I'm not trying to argue with you but I am running the sk720 flybarless unit and am trying to eliminate all the vibes I can. I have been weighing blade grips and balancing clutch fan assembly,checking runout etc...etc..
You would be surprised at the difference in weights between grip bolts,feathering shaft bolts etc.
Has anyone tried more than two bearings?

[eightythree]

no sense in eliminating all these imbalances..
an internal cumbustion motor is naturally unbalanced anyway. build it and fly ;)

the newer SK units should have a vibration filter anyway, right?