Bad vibes! Do you need boom support brace?

[Jotto]

Originally Posted by SHARKGR

did you try leaving some space for the TT?
pull the boom out about 1.5 - 2mm,then push the tt dead in and pull it out a bit,and place the tail rotor housing,ensure that it adapts to the TT with no effort so that the tt doesnt bend......
thats kinda the info i got from align with my new tt assembly,its not mentioned in the manual tho

I don't understand what you mean by "pushing the tt dead in and pulling it out a bit". Maybe I can blame the "friday after lunch" effect. :-)

Could you explain a little bit more in detail please?

[DonDuc]

Originally Posted by SHARKGR

did you try leaving some space for the TT?
pull the boom out about 1.5 - 2mm,then push the tt dead in and pull it out a bit,and place the tail rotor housing,ensure that it adapts to the TT with no effort so that the tt doesnt bend......
thats kinda the info i got from align with my new tt assembly,its not mentioned in the manual tho

Yes, did that. I followed the Finless video and it's in there, too.

I did some more test runs and found that now the tail servo was vibrating as hell. First I thought that the holder is too weak but then I disconnected the pushrod and it went away. Apparently my CF pushrod falls in resonance. The one I had made was quite strong, made from a 5mm OD CF tube with the ball links slid into the tube.
The interesting thing was that the vibrations were now very localized, touching the frame there was very litte and the gyro was totally quiet. On the tail boom and the tail rotor housing I could feel very little. It was the tail servo, the pushrod and the boom supports vibrating strongly, apparently excited by the resonance in the push rod.

Now I made another push rod with 3mm OD and 2mm ID to lower the resonance frequency . It's a bit weaker but still should do the job nicely (especially with my Heim Joint CWM) To eliminate/ reduce harmonics I slid a short piece of the larger tube over it and glued it off- center. Now the epoxy is setting and I'll see what happens next.

I have the feeling that the airframe is quite stiff with little damping so every so slight vibration will be amplified somewhere.

Interesting new problems, my 450s had no vibrational issues at all, once all blades were balanced and all shafts running true.

[SHARKGR]

Originally Posted by Jotto

I don't understand what you mean by "pushing the tt dead in and pulling it out a bit". Maybe I can blame the "friday after lunch" effect. :-)

Could you explain a little bit more in detail please?

hehe,i meen with the boom on the heli and the tt off,u slide the tt in the boom and push it as in as it goes,then back it off a bit,so that its not tight on the umbrellas...

[DonDuc]

SUCCESS! Big improvement with the new push rod. It's still vibrating a little so I add another "weight" but the vibrations are reduced to very low levels!

[SHARKGR]

any update on the sit scoti333?

[Matt Nasca]

One of the things that happens and is a cause of the resonance or hum is the front white umbrella gear being ever so slightly crooked in the bearings. This combined with it being on too far (too tight) will cause the problem.

I've seen and fixed two 500s, including mine, with the exact same symptoms. Re-aligning the front gears and making sure they spin true and are smooth, fixed both.

Now that I am aware of this and make sure to install the gears properly, the resonance has not appeared again.

I am running two torque tube bearings with random spacing (no length measurements between bearings, or ends the same). I haven't really noticed any difference in performance by doing that but the theory makes sense so I continue to run two.

[scoti333]

Originally Posted by SHARKGR

any update on the sit scoti333?

Yea, I put my old tail assembly with the old blades on that I crashed with but wasn't damaged, and it fixed everything... go figure!

[SHARKGR]

rofl.....
are you sure you dont bent the TT when putting in the tail cases?
do they get in the boom without any,any strength?

[scoti333]

Yea, everything is new except from the tail slider to the tail blades.. So it couldn't have been the TT or the umbrella gears..

[SHARKGR]

..then there is only one thing left...
pray to the helicopter gods that it never happens again xD
enjoy your flights pal..

[scoti333]

No sh!t...! I think though, too, that it had alot to do with my headspeed being way too high. I took it to the heli field for the first time a couple weeks ago and my buddy maxed his tach on it at 3190! And that was only at 95% flatline. It always flew very well with no vibes on normal mode, so I dunno.. I hear of people on here all the time running 100 flat, but I think those people are running set rpm govs with that setup and I just overlooked that detail.

[SHARKGR]

what pinion do you use,i also see some huge Cratings on your batteries xD i meen no need for 40c on 3000mah xD

[scoti333]

This was stock align esc and 13T at 95% flat before I switched to 14T and an Ice 75 governed at 2680.. No vibe issues now and I even put the tail assembly back on that I had trouble with and it was fine..

[Jotto]

I don't understand - what did the trick for you?

[SHARKGR]

he lowered the headspeed....
maybe thats why align has a ! in the 2800-3000rpms in the manual...this issue!

[scoti333]

Yea but what was wierd was that when I was running the stock setup as mentioned before, the old tail assembly/slider that was on when I crashed (nose to dirt crash) fixed about 75% of the problem. The other 25% was definitely the headspeed.

[SHARKGR]

yes,companies make their products with some accepted tolerancies,and align knows that their tolerancies say that the parts wont stand 3000rpm...
maybe the on tail box can stand 2800 before vibe,maybe the other can stand 2900...it may have to do all with maker tolrancies...even a slightly different gear mesh,not seen by the eye could make this difference.....GOD i LOVE helis xD
this tolerancies could be anywhere,bearings,shafts,blablabla...

[Jotto]

Too bad my problems show up at 2600

[SHARKGR]

i think 2600 is too low to show up problems like this....
how d u know its 2600?measured it with tachometer?
if it is so,check everything,tt if bent,all bearings etc...

[Jotto]

I'm using governed headspeed (set rpm on a cc ice). I have checked the tt, just replaced tail bearings.