Extra bearing on Torque Tube--Trex 450L

[AlvaSpeed]

I dont know if this have been posted before.

Today I was chasing an electrical problem with the esc and spooled up the heli (without blades of course) and felt a large vibration at high rpms.
Took the tail assy (boom-tail) out and spooled the heli again and it was vibration free.
Took the Torque Tube out and saw some scratches on it (rubbing against the boom).
Installed a new Boom and Torque Tube, (glued the bearing per Align instructions) spooled up and after a couple of seconds it started to vibrate again.
Took the new Toque Tube out and it was scratched in the same place as the older one.
I think the TT is too flexible.
So I went and installed an additional bearing on the torque tube on the same spot it got scratched and problem solved.
Check out the pics......

[AlvaSpeed]

The tool points where the torque tube gets scratched

[AlvaSpeed]

Torque tube with the extra bearing.
Have not flown the heli yet but it is silki smooth on the bench.
So It should be o.k.

[heli smasher]

Alva, I had the exact same thing. Three bearings were needed to make the tail silky smooth...

[Boinker]

My 450 Pro was doing the same thing to its torque tubes, I have yet another TT on the way and an extra bearing to help support it. Im pretty sure if the thing gets bent even a little then it flairs out under the Stress of rpm. Got to remember its a High RPM TT so a little eout of balance does a TON

[cobieg]

Originally Posted by AlvaSpeed

I dont know if this have been posted before.

Today I was chasing an electrical problem with the esc and spooled up the heli (without blades of course) and felt a large vibration at high rpms.
Took the tail assy (boom-tail) out and spooled the heli again and it was vibration free.
Took the Torque Tube out and saw some scratches on it (rubbing against the boom).
Installed a new Boom and Torque Tube, (glued the bearing per Align instructions) spooled up and after a couple of seconds it started to vibrate again.
Took the new Toque Tube out and it was scratched in the same place as the older one.
I think the TT is too flexible.
So I went and installed an additional bearing on the torque tube on the same spot it got scratched and problem solved.
Check out the pics......

I did not know you were supposed to "glue" the bearing. What glue is used for this?

[AlvaSpeed]

Originally Posted by cobieg

I did not know you were supposed to "glue" the bearing. What glue is used for this?

Check the manual. There is a measurement for the bearing install.
You clean the torque tube with alcohol.
Put a Little bit of CA glue on the TT and slide the bearing and glue it without letting any glue inside the bearing.
Put the rubber damper over the bearing and you are done.

[atkin]

I wonder if your first bearing placement was exactly at the 2/3 mark and so you got a resonance between the other 1/3 sections (sine wave)

[AlvaSpeed]

Originally Posted by atkin

I wonder if your first bearing placement was exactly at the 2/3 mark and so you got a resonance between the other 1/3 sections (sine wave)

Manual says 10mm to 15mm offset from center.

[atkin]

Originally Posted by AlvaSpeed

Manual says 10mm to 15mm offset from center.

True, I was just judging by your photo. Glad you are aware of where to put it.

I've never seen a brand new torque tube come out of the package straight....

[SMOKEMASTER60]

I recommend you put two. I had a torque tube wear itself in half a while back and now use two without issues. I may had installed it wrong, but now there is no worries.

[Pitch-Itch]

Interesting, noticed a vibe in my dominator with less than 15 flights on it. I took the boom off and noticed HEAVY scratches on the torque tube. I went ahead and ordered a new book, torque tube, and 2 bearings for the torque tube.

I've been unhappy with the tail (hunts constantly), and the head has been very wobbly and not locked in at all during tick tocs and such. Hoping the vibes from with TT issue was the cause.

[FrankFuss]

Originally Posted by heli smasher

Alva, I had the exact same thing. Three bearings were needed to make the tail silky smooth...

Based on heli smashers report, I will be using three TT bearings. My Skookum SK-720BE is vibration sensitive and will need all the help it can get.

[heli smasher]

Frank, I have one bearing as per the manual, and the other two around 80mm in from each end. In fact I think the front bearing was 70mm and rear bearing 80mm, just to offset them a small amount. Hope that helps

[Trexwilly]

Are you guys spooling up without the tail case?

[Pitch-Itch]

Originally Posted by Trexwilly

Are you guys spooling up without the tail case?

I did. I tried first with no mains, still had vibes. No mains and no tails, still had vibes. Pulled boom, tail case, and TT out, no vibes.

Pulled the TT out of the boom, and noticed HEAVY scarring on the TT itself and inside of the boom. TT is noticeably bent as well, but wasn't when it went in (made sure of that).

So if by tail case you mean boom, TT, but no actually case at the end - no I didn't try that. Couldn't really, due to the TT being so out of whack. I'll snap some pics of the TT. It's pretty bad. The vibes were crazy as well, hurt my hand a little to hold it on the boom. Really surprised I wasn't getting any weird interaction in the 3sx unit.

[Chep]

Weird. I've built mine and two more for other buddies and we haven't experience that issue.

Chep

[Pitch-Itch]

Originally Posted by Chep

Weird. I've built mine and two more for other buddies and we haven't experience that issue.

Chep

I didn't either for the first few flights. It was solid and vibe free as any heli that I've ever seen. Got it out again to mess with some ESC settings, gov and whatnot, then went outside to do some test hovers and I could see the skids shaking violently. It just came on with really no warning or cause.

ETA: Have you actually pulled the TT out and looked at it though? I'd be interested to see what those 3 TTs look like, even if you aren't having vibe issues.

[Chep]

Actually I did. I stripped the front TT umbrella gear and had to remove the TT. It was in good shape.

[CousinLarry]

Mine did the same thing. Had that front umbrella gear strip out while i verted hovering. Doh!

Rebuilt t last night. TT had a good 2" of shiny metal scraped off on the front side.

Cleaned everythin out, replaced a couple bearings and gears, and this time used two bearings on the TT. Wow - a noticeable difference! Much smoother sounding. My friend i fly with asked if it got quieter too. Haha

I think three might be good, i'll be ordering a new TT to have as a spare.