450 Throttle up issue on 450L Dominator

[Eggy 71]

It seems my little fix it just keeps adding on. I'll take a step back and tell the whole story.
In the last few months I have assembled this 450L with a 3GX and got it dialed right in nicely ( with some helpful advice from Tony and others). While flying one day I hit the tail a little hard during landing. It actually bent the tail shaft ever so slightly. OK, I replaced the tail shaft and started up. Essentially, it did what was in the video and I lost some tail control and had a hard landing clipping the main rotor on the ground. That bent the main shaft. With that replaced (and the issue with the thrust bearing on a previous thread) I'm back to this stage. What getting me is everything seems to be aligned as I spool up. If I switch to stunt mode and 80% throttle it happens instintly, if I do a slow spool up you see the results after a bit. Any ideas on what's happening there? A second note is that the tail blades are VERY close to the ground (reason for the plywood). Any tricks for adding some clearance?
throttle up issue - YouTube

 

[holtneil]

Hi mate I had same on a copterx 450 black angel ,it turned out to be a bad tail blade grip, there was play in the grip which I think was a bearing so replaced the whole thing and it was back to flying right
as for tail blades you can fit a spacer between the skids and main frame to lift heli up but your need longer screws , or fit skid nuts which are rubber and fit on the skids they are for the older trex but should still fit ok
https://www.google.co.uk/url?sa=t&r...OXjafoH2cujng2zMA&sig2=p5C5TXaI3uBPbU0-oJ6kYg

At some point I would replace the 3GX they do strange things at time like tip overs etc , a great cheap gyro thats really great and flys so nice is the Kbar

 

[Tony]

I have to agree with Neil on this one, the tail grips sound like they are fluttering. May also be the piece that links the tail link (long) to the slider, the bolt may be loose. Check all screws and balls and make sure they are right, and remove the linkage rod and make sure the tail blades pivot freely.

Also, your main blades are way too loose. Tighten those down a bit.

 

[Eggy 71]

Ok I've disassembled and check the tail linkage. There was a very small amount of play between the control link and the blade grip on one side. The blade grips themselves have only the smallest amount of play on the rotor hub but are tightened right up with the screws. I'll give it another go in the morning. There was definite vibration in the tail once this noise started but nothing really seemed loose enough to cause it. If you listen to the shut down and stop in the video you hear a non symmetrical noise as the rotors come to a stop, is it possible the one way bearing in the main gear could be slightly damaged? just a thought. any comments welcome.

 

[Tony]

I don't think the OWB would do this since it's not in play when it's spinning under power. It's more of a clutch than anything. It should either grab, or not.

The only other time I have seen this issue is when someone put blades on backwards. But you have not done that here, trust me, I looked lol. The only other thing I can think of is the blades were just way too loose.

Speaking of loose blades, did you tighten your main blades? They torque over a good amount when you start to spool up.

 

[holtneil]

Hi you can always remove the tail from the frame take off main blades and just run up the head to see if the sound is still there to rule out a one way bearing in had a big tip over and still didn't damage the one way bearing
As for the tail blade grips there should be no play even a little can make the tail play up
Just remember the forces you have when heli is at a high speed

 

[trainrider06]

Hi Eggy, you can do a couple of things about the tinny boom on those helis, first of all get you some 500 boom braces and mount those on the tail. they are longer and help to support the tail better, also run two bearings in the TT drive. Those rods are so long they can get to flexing inside of that shaft causing vibration problems and tail erratic responses. Also check that your tail case is not leaning anywhere a bit to the right as you look at it from behind, I had a tail case on a 450 pro snap a drive gear because my tail case was twisted to the right slightly and caught the tail blades on landing.