Extremly bad tail vibration - resonance?

[clayboy]

how tight is your belt? i get nasty vibes an horrible sound around 1900rpm on the short boom and 1800 on the long boom when my belt is to loose. think it is these big teeth on the belt .if the belt start to vibrate they hit the other side . mine is quite tight. have a slightly bent tail rotor but i have hardly no vibes

[skigolfmike]

My belt is really tight. I could get it slightly tighter, but not much.

I have the short boom and, yeah it's about 2000 rpm where I get the vib.

I got it the other day and then it went away. When I spooled down and back up, no vibration. That's when I loosed up the tail grips a little more, it stopped. Unfortunately I noticed the tail case had cracked, so I couldn't fly it.

I had the problem with the Trex 600 tail too. With the lightweight TR blades it shows up as an oscillation. With the stock blades it's a bad vibration. The lightweight TR blades are pretty flexible and I think they absorb a lot of the vibration while the stock blades do not.

FWIW, I did try the Guai CNC tail again and got it to work pretty well. It pretty finicky to get it setup right though.

I will be calling ReadyHeli about the tail cases today though. I wish there was a good CNC tail case for this heli. I do have a buddy with a tool and die shop...

[vicrc]

I don't run my belt tight at all and I have no issues with vibration. Make sure you don't have too much Gyro gain and that can cause vibrations. You only need enough gain to keep the tail from rotation during heavy cyclic. Lower the gain and see what it does. When your running even higher RPM you need to lower the gain as well. Some radios even let you program different gain settings for stunt mode, like a DX7

[skigolfmike]

I don't run my belt tight at all and I have no issues with vibration.

Which makes me believe having the tail grips (not having the tail blades loose enough) had a lot to do with it.

Generally, the 550 likes the belt pretty tight.

There is a chance the tail shaft may be bent, although I have no clue how I could have bent it. No crashes or tail boom hits.

[xodarap1]

Something must be wrong somewhere.

The belts on my helis are far from tight and both of them have the stock plastic tails and there isn't any funky vibrations on either of them. A slight bend in the tail shaft or a belt guide wheel that isn't spinning correctly would be easy things to check.

[dadde]

Thanks for all the inputs dudes! It realy helpt to know that some people do want to help.

I have tried a bit of new stuff;
new mainframe
new tailcase
new front pully set
new pully shaft with gear
new tailpully
new tailoutputshaft (3:rd one)
new tailblades
new motor (again)

Nothing helped.

I just came in from the latest atemt to get the vibrations to vanish
I tried:
Loosening the tailblades
Tightening the tailblades
7 diffrent belt tensions all from verry loose to extremly tight
Change between the new blades and the "old" set of new blades.
Dial down the gyro gain

Nothing helps.

I do think I'll try the T-rex 600 tail blade holders next :/

[skigolfmike]

The crazy part is at times my heli has flown great. Then, out of the blue, it starts acting up again for no apparent rhyme or reason.

Is your tail case cracked? You can tell if you grab the tail rotor and pull back a little on it. If the case splits it will be right in front of the bearing. If your tail gets the shakes real bad it WILL break the tail case.

[GatoVolador]

I feel for you man. I had bad vibes as well after a rebuild and changed lot of stuff until it went away. I'm still not exactally sure what the problem was which doesn't exactally inspire confidence. I love this heli but these sorts of problems make me wonder if I should go for an e550 or Logo 500 instead. The Gaui parts are cheaper but if you end-up replacing a lot of stuff to chase down a vibe the extra parts/time cost quickly erase the price lead of the Gaui compared to other helis....

[skigolfmike]

I'm starting to wonder if I should have bought something else a little more expensive up front rather than all the money I've spent chasing down these kinds of problems.

[helvetic]

I do think I'll try the T-rex 600 tail blade holders next :/

Try the T-Rex 600 tail case. I could solve my tail problem only with the replacement of this part.

http://www.helifreak.com/showthread.php?t=63121&highlight=tail+vibration&page=5

Hope you get flying soon... good luck!

[GatoVolador]

I have my Hurry running on 10SA123 using the CHP frame. I'm seriously thinking of getting an E-Raptor 550, the A123 Raptor frame extension from Gary @ TPPacks and then running my A123 packs in an 10S2P configuration. That will probably give me flight times around 10-12 mins. Most of my avionics I can swap out except for my servos and possibly a larger ESC (CC85HV). How many problems do you hear from Raptor owners? I'd also consider a Logo 500 but the Mikado parts are more expensive. At this point I'm looking for a proven design and that's the Raptor.

[dadde]

skigolfmike: Tailcase is fine, I checked a minute ago.

helvetic: Yeah a 600 tailcase is'nt that expensive to try, thanks.

I maby will have to get a whole new kit and use my current heli as a spare part :/

[mjdee14]

skigolfmike: Tailcase is fine, I checked a minute ago.

helvetic: Yeah a 600 tailcase is'nt that expensive to try, thanks.

I maby will have to get a whole new kit and use my current heli as a spare part :/


I really love the 550 but this tail vib problem is getting rediculous when a person has to replace every part and still can't get rid of it......

During my rebuild after "spiderman" shot me down I noticed there might be an oportunity for the tail bearings and or front tail pulley bearings to be a littel loose in the frame...

Finless recommends using sho goop or some other form to secure the bearings in the frame...I have also heard others complain about the quality of the bearings....I wonder if some of this vib problem isn't built "into" the heli with loose bearings and/or loose fitting bearings.

It seemed to me my tail case bearings could have a tiny bit of movement...at few thousand rpm that would be greatly multiplied...


Just thinking out loud.......

[mysticmead]

don't forget that the tail turns a LOT faster than the main, so yes, a little slop back there could result in vibrations..

[skigolfmike]

You may have something there. I don't remember that specifically from the Finless videos, but I do know the bearings are pretty loose in the tail case. It wouldn't take much shoe goo either. I may get some at lunch today and try it tonight.

Also, I think headspeed is definately involved. I didn't have any trouble with this until I started turning up the head speed. At 1800 I had no problems. Now I'm trying to run 2000-2100 and that's when all the problems showed up.

I'm going to give it a try tonight with one of my repaired tail cases. I also put on the CNC main blade grips and 500mm RCP II blades. I have the CNC see-saw too, but I'm going try and solve this before I move on.

[mjdee14]

I know th shoe goo is supposed to keep it from rotating...I have never used it..does it get hard or is it like RTV?

I would like to see something that really tightenend up the race in the plastic.

I was not impressed with the sloppy fit and the loosness in the bearings themselves.

Let us know if you have any luck.

[skigolfmike]

Shoe Goo doesn't get completely hard and if you put on a thin coat it stays pretty flexible. It's much firmer than RTV though. It also takes a while to setup, ~ an hour.

When I raced RC cars, we used to glue nicad and NiMh batter packs together with it because we could easily break apart the packs later and it wouldn't rip the original heat shrink.

I think the way to do it would be to put a small dab on a Q-tip and swab it around the bearing pocket in the case putting on a thin layer. Then press the bearing in the pocket. Any excess that squeezes out can be trimmed about 5-10 minutes later with an Exacto knife.

[skigolfmike]

I flew the heli tonight with one of the repaired tail cases. It actually flew pretty well. No vibration, even with the head speed cranked up. I was getting 2200 headspeed at 100% flat throttle curve and 2100 at 80% throttle. It was as smooth as can be. I did have a little bit of a rudder trim issue in rate mode. Not a big deal as I can easily correct that.

All I did was hover and I did a little punch out. Anyone want to guess if my tail repair held? (Pics below.)

I do have the Gaui CNC slider and TR grips on right now. Have a look.

[xodarap1]

Wow.. that's brave man. I've had some bad dreams of tail blades coming off and ripping into me. I've done a lot of heli frame repairs to minor areas, but a tail case is one repair that I will pass on. I hope the repair held up and that it continues to if you keep flyin' it so that nobody gets hurt. This hobby is dangerous enough and blind pilots can't fly heheh. Be careful.

[skigolfmike]

Actually the repair didn't hold. I would hover a minute and check. Lasted 3 minutes. You can see the crack in the middle pic above with it on the heli. The last pic is after I took it off and cleaned all the epoxy off it.

I have new tail cases coming, which should be here today. I don't think it's possible to repair the tail cases because, whatever they are made of, glue doesn't stick. Not even if you prep the surface first. I tried JB Weld, plastic epoxy and layers of CA.

The good thing is the vibration is gone. I think I was getting the tail blades too tight and they weren't able to get completely straighten out. As the head speed came up, it would hit a point where tail just went nuts. I'm hoping the current setup with a new tail case will solve the problem.

Too bad there isn't a good CNC tail case out there the stock components can bolt onto. Might have to make one.

[mjdee14]

http://www.helidirect.com/product_info.php?cPath=30_321_322&products_id=5889

I have the above case, I haven't used it yet but it looks pretty good....you need to use their control arm, but everything else can be Gaui...just don't use their hub...it's the one that blows apart until they redesign it. But I thought the case looked safe to use.

I'm saving it for my CF version, but I don't see any reason it would have any problems with it. (famous last words)

[skigolfmike]

I saw that and checked it out. I will probably get one soon. Helidirect also sells a swash leveling tool for the 550. I have one the my Blade 400, it's definitely a nice to have.

[phunk]

I just got that swash leveler, sooooo much better than eyeballing it. This thing is so stable now it'll just float there hands off for 10-20 seconds easily (if there's no wind).

[skigolfmike]

I think I got it sorted out. Put on the new tail case tonight, set it up and gave it a go. I got a little vibration in the tail as it was spinning up. I backed off a little until it stopped, then spun it up again. Smoothed right out. Popped it up and it flew great. I had a little bit of a blade tracking problem, which I sorted out. Also, the TR was back in trim in rate mode. (That's a good thing.)

I have the RCPII 500mm blades on it and it was really singing. My throttle curves are 0-60-80-90-100 normal, 100-80-100 idle1 and 100 flat idle2. I'm getting 2100 in idle 1 and 2200 in idle 2. I'm currently running 20T pinion w/ the 68T Revco gear and a 20T OWB. According to the headspeed calculator I can go to a 22T to get 2400 rpm.

I also have a CNC tail case coming from HeliDirect. I think that will hold up better than the stock tail case.

I'd change the pinion and get in a test hover flight in the coldesac, but it's raining and I don't need to short out all the electrics just when I'm getting it flying good.

Update: I put in the 22T pinion and spun it up. Man it flies great. That head is really singing at 2400 rpm. Can't wait to fly it where I have room to do something.

[WalterL]

I had terrible vibrations at different RPM. After many hours of work i found the reason: One of the very little screws fixing the Tail Supporter Pipe was missing.
Afterwards evrything went fine.