Tail Problems

[visuvius]

I installed a 401/3400g combo and as of yet I still havn't gotten much of a chance to see what its really like because of issues. My current issue is that as I apply throttle, the tail vibrates or shakes in a vertical motion. As more throttle is applied, the vibration gets worse. The front end at this point is not vibrating at all, it is pretty solid. As I get to midstick, the vertical vibration is pretty bad. I went to about 55-60% throttle and this last time, the tail rotor stopped spinning.

Basically every time I run the chopper, the belt gets loose. I bring it in, remove the four screws on the left side near where the gyro goes, pull the boom out and tighten the belt. When I apply throttle again, the vibration starts and the belt is loose again. I can't figure out what the problem is. Like I said, the front end seems solid, the skids aren't vibrating at all. The feathering shaft, main shaft and main gear have all been replaced.

What could my problem be? The tail rotor assembly seems okay as does pretty much everything else, but like I said, as I apply throttle, I get a vertical tail vibration/shake and the belt gets looser and looser culminating in the tail rotor ceasing to turn (if I apply enough throttle).

Please help.

[Heli Jim]

That would seem to indicate an out of balance in the tail rotor blades.

[visuvius]

The tail rotor blades are new, as are the main rotor blades. I haven't however checked the tail rotor shaft, thought I can't imagine what would have been or damaged that.

[LockMD]

This is a 'new' set up yes? lower your gyro gain. Someone mentioned about the boom slipping and the rex had a solution as it was comon on it....I cant remember what. Just dont get over board on tightening the boom stipping them screws in the plastic will not be good.

[visuvius]

Yeah its not the gain on the gyro. I know what that looks like and its a different kind of vibration; plus I've tried lowering the gain and it didn't stop the problem.

I'm definitely going to be careful when putting those screws back in. Stripping them would be all sorts of suck.

I'm going to try replacing the tail rotor shaft and see what happens but otherwise I'm pretty much stumped.:arggg:

[LockMD]

Yeah its not the gain on the gyro. I know what that looks like and its a different kind of vibration; plus I've tried lowering the gain and it didn't stop the problem.

I'm definitely going to be careful when putting those screws back in. Stripping them would be all sorts of suck.

I'm going to try replacing the tail rotor shaft and see what happens but otherwise I'm pretty much stumped.:arggg:


Me too.... with the heli on the table spin the main rotor and look down at the tail slider if there is ANY wobble what so ever it will cause this issue, believe me it bends very easy in a crash even if you thought the tail had no damage.

[sokal]

I installed a 401/3400g combo and as of yet I still havn't gotten much of a chance to see what its really like because of issues. My current issue is that as I apply throttle, the tail vibrates or shakes in a vertical motion. As more throttle is applied, the vibration gets worse. The front end at this point is not vibrating at all, it is pretty solid. As I get to midstick, the vertical vibration is pretty bad. I went to about 55-60% throttle and this last time, the tail rotor stopped spinning.

Basically every time I run the chopper, the belt gets loose. I bring it in, remove the four screws on the left side near where the gyro goes, pull the boom out and tighten the belt. When I apply throttle again, the vibration starts and the belt is loose again. I can't figure out what the problem is. Like I said, the front end seems solid, the skids aren't vibrating at all. The feathering shaft, main shaft and main gear have all been replaced.

What could my problem be? The tail rotor assembly seems okay as does pretty much everything else, but like I said, as I apply throttle, I get a vertical tail vibration/shake and the belt gets looser and looser culminating in the tail rotor ceasing to turn (if I apply enough throttle).

Please help.
check to see if your boom is cracked on the side that it goes in to the frame

if not apply 1 layer of tape on that end to help keep the boom from loosesning.

[visuvius]

I'm sorry for being a bit dense but can you please explain that a bit further. I checked the boom and it is not cracked, although on the tail end of it there is a little dent. This has been there for a couple of weeks and didn't affect anything.

So if the boom is NOT cracked I apply tape? Can you please tell me where exactly? I see that the boom goes into the body right under the gyro; where would the tape go?

Thanks!

[supra6]

Same sort o fthing happened to me, but it was after a know crash, the tail would not stay in place, after removing the boom I noticed there was a slight inward dent just where the slit is cut in for the belt tension, relace the boom and all fine.
On a different note after dicking around with those tension screws, you can not see the head, they can strip either the screw head or the plactic, I used #4 self tapping hex head screws with a washed on the side, much easier to adjust and you get a good tight fit with out the risk of stripping the screw.

[SeaComms]

I had a reasonably soft landing with no damage at all, but noticed a couple of nicks in the lower tail fin. I then realised that as it landed the tail fin was pushed over toward the tail and the blades nicked it a few times.

I now notice the tail rotor shaft is bent, not much, but if I spin the main rotor and look closely at the tail pitch slider I can see a slight wobble in it. ie - the shaft is bent.......

Cheers, Dave.

[sokal]

some times the boom can get cracked in the frame normally were the alignment slit is
if it cracked it will not be able to hold the boom tight enough in the frame.

if its not cracked use a layer of tape on the end of the boom that in the frame to help with the friction to hold the boom in the frame just cut the tention hole and alignment hole out of the tape once applied.
will post a pick one i get back home.

but if you loosing belt tention that were the issue is

like the one guy said new boom will more then likly solve it

[visuvius]

Thanks guys, I'm going to start the arduous task of taking the tail apart when I get off work. I'm NOT looking forward to it LOL. :dontknow

I just hope my LHS has the tail boom in stock if that is indeed the problem.

[visuvius]

Well before I started tearing into the tail, I followed Horizon's advice and decided to "loosen up" the head. The guy on the line said that it could be that the head is too tight or some sort of dampening problem. I loosened the screws that go into the feathering shaft just a bit (they were a little too tight) and I removed one of the 4 shims on each side.

I fired it up and it seems like the vertical vibration/shake is definitely gone when its on the ground. When I get to just past half stick, it does come in a little bit right before I get off the ground and then its fine. The belt has not loosened. (Without using excessive force) it seems like I can push the belt about half way across the tail boom.

I'm not sure if I want to fuss with the tail at this point but I probably will. My bigger problem now is that I'm pretty sure I need an external BEC. I thought it was my new Loong Max batteries but as advised in the other thread, i DO need a BEC. My Thunder Power V2 did the same thing; motor cuts and then a couple of seconds later it fires back up and the speed control gets excessively hot. Boooo!!! Does everyone with upgrades have these things??

ALSO, how far up the stick should I be when the skids start to float around a little bit? Right now I'm up to like 65-75% throttle before it starts getting light and off the ground. I'm using the stock throttle curve. I don't remember it being like this. I'm pretty sure I did the blade pitch right, but it WAS my first time doing it myself. Can someone please tell me what my blade pitch is supposed to be when the throttle stick is all the way down?

Thanks for your help guys and sorry for all the questions.

[Wolfpackin]

If you're checking the pitch in Normal mode (with motor disconnected) or Throttle hold and you haven't changed the stock curves then low stick position should be -3d, center 0d and high stick +10d.
Stock setup for idle up should be -10, 0d, +10d.
With these curves the heli should lift around 3/4 stick or about +5d pitch, approximately.

If you are running four "real" digital servos you may indeed need an external BEC.
The stock setup or an upgrade of analog cyclic servos shouldn't need one, it all depends on the amp draw of the electronics you're using.