vibration help in london

[michaelsnny]

after crashing my beloved trex 450 and rebuild i have a vibration issue at mid throttle it will bounce a little on skids as you throttle up it turns to vibration you can hardley see but is their very rapidley now when you take blades off no vibration through full range of throttle this would tell you blade problem re balanced alined tryed everything when you track them they seem to be out of track in middle of blade by the way they are carbon is it my eysight thats playing up or has anyone else had this or any ideas whats wrong this heli was great till this not even sure what else to replace exept all of it any help appreciated

[Abu Soud]

from my little experience

blades balancing and tracking is important

check your torque tube maybe its bent a little

make sure you have the same pitch degrees for full positive and full negative

feathering shaft and main shaft should be straight (maybe you didn't notice a damage when you fixed the heli and you skipped checking them)

make the FBL unit setup again

sorry I'm not an expert but maybe its one of the above

[TheCajun]

It might help to know what was replaced in crash. Were the blades replaced?

[michaelsnny]

thanx for help replaced feathering shaft and main quilty of not changing bades reason they looked perfect it was a very minor crash striped main gear changed rest as precaution im gonna go throught blade setup again let you know hoe it goes

[Sefrez]

Assuming the blades are not the problem, tracking being out in the center sounds like the head is out of alignment or the grips are. Check those.

[savannahmick]

ARRGGGHHHH! I am going crazy trying to figure out what is the cause of the vibration but I can't afford to buy a whole bunch of stuff to replace on my 2-3 month old 450 DFC Plus. I have rebuilt it completely twice checking all shafts and making sure that I have everything setup right. I did get a new feathering shaft cause it came with the older version with the 3mm thrust bearing so I got the end to end 4mm shaft. I also got the alum grips to replace the plastic ones and the alum DFC arms v2 with the 2mm threads. Recently had a minor crash that broke a main blade so I replaced them and balanced them with a small digital scale. I forgot to mention I bought the other stuff that I stated above after the crash. I do have the single screw rotor housing not the clamping 3 screw one could that cause the problem it has VERY LITTLE play in it? I am getting discouraged by the issue cause I am trying to learn basic 3d and it is hard to takeoff without the heli gyro getting confused by the vibration but once I am above 50%-60% throttle it goes away! Maybe we have the same problem Michael if I can get it fixed I'll let you know how I did it! Thanks for any help you experienced flyers can give us!

[Bladecpnitro]

If the vibes are going away at higher throttle settings it might be that the blades are a bit too tight.

Usually vibes get worse at high RPM.

[savannahmick]

Originally Posted by Bladecpnitro

If the vibes are going away at higher throttle settings it might be that the blades are a bit too tight.

Usually vibes get worse at high RPM.

How tight should they be? Mine can be moved with a little pressure while holding the grips. I just completely rebuilt the heli AGAIN checking everything including shafts by chucking them in a drill they are perfect and I have no play in the head or grips. I am going to go crazy trying to get this resolved since I am ocd about my rc stuff! Thanks again!

[savannahmick]

[ame]http://youtu.be/YEQ9bMmfCKk[/ame]
Here's the video you can see the vibration better in the second throttle up. Its not real violent since I loosened up the blades more but it dances on the skids. Look at the antenna you can see it shaking! Thanks for any ideas! I flew it after the video and flies great just can't stand it dancing at takeoff! Thanks again!

[Harbormaster]

I'll guess a slightly bent main shaft. Without blades attached, you have less rotating mass, so the problem may not manifest. If all else fails, always replace "the usual suspects": main shaft, feathering shaft, and tail shaft.

[Bladecpnitro]

On Blade tightness, your supposed to be able to hold the heli nose up and the blades stay put but if you give it a couple of bounces the blades should drift down a little equally.

Does this heli have a belted tail? I've found a belt too tight will cause vibes. Also I've found tail grips that were unbalanced and even though I balanced the tail blades I couldn't quite get rid of the vibes. Main to pinion mesh too tight will cause vibes.

A motor out of balance will cause tremendous vibes.

How are you balancing your blades? I don't see any tape on the CG of either blades. Were the blades perfectly balanced already?

I'd take the head off and spool the heli up slow to check the main shaft for wobble. Then spool it up to the level your normally getting vibes and feel the frame close to the motor. Naturally there is going to be some vibes from the motor with it turning the main gear but you'll know if its excessive vibration. Do the tail the same way. Hold the tail carefully by the vertical tail fin and spool up the heli with the tail blades strait and feel for vibes.

I just have chased down vibes in my 450 that drove me nuts. Turned out to be worn out tail shaft on the tail end. New bearings were no longer helping.

That was some of my vibes but the rest were coming from an unbalanced motor.
I balanced the motor can and the heli ran smoother than I'd ever seen it. Great time to crash right? Ha! Nope!

I would imagine your vibes are in the tail blades or main blades. Its harder to get blades perfectly balanced than it seems. Teeter balancing only gets you close if your applying weight to the CG of the light blade.

[savannahmick]

I was able to get it better by using a colored tape that I cou see really good and I got the tracking almost perfect which was part of the issue. BUT I think it is the tail setup that is causing a little vibration also. I am going to get a metal tail case and if needed I will try the tape hit and miss method on the blades. I am getting better at all the little things that make it a good smooth flying bird. I have already done this once with racing 1/8 nitro and 1/10 electric off-road vehicles. Lol! I guess helicopters are no different and experience is priceless! Thanks again for the help!

[Larryu]

Check the tail shaft to be sure it's not bent. It can cause what you are describing. I had the metal tail housing on mine and it did make much difference. It will make it tail heavy so you have to add some counter weight in the front.

[Larryu]

That was it didn't make much difference. Sorry stupid phone.