Vibration and Tail holding problem

[OmegaRedIsDMan]

Vibration and tail holding problem.

Background info: my dbl brushless 4G3 had been flying ok for 2 months. Suddenly the tail stopped holding. and it would spin around while trying to take off.

I replaced the 2g tail with another 2g tail. Now I the tail jumps back and forth. I've tried adjusting the gyro gain higher and lower. Also I noticed that the bottom of the tail fin seems to be vibrating in flight.

I appreciate any suggestions on how I can fix this problem.

here is a video that shows the problem. I both recorded with the canopy on and off. I also got some up close video of the main gear and pinion near the end.

4G3 vibration and tail holding problem (7 min 23 sec)

[SQRT(-2)]

The 2.9g tail really works better, I did not believe it and tryed the 2g myself. It is worth the extra ten dollars.

Also inspect the head for any cracked parts. I had a crack in my head block that caused major vibrations that messed with the gyro.

[OmegaRedIsDMan]

The 2.9g tail really works better, I did not believe it and tryed the 2g myself. It is worth the extra ten dollars.

Also inspect the head for any cracked parts. I had a crack in my head block that caused major vibrations that messed with the gyro.

Thanks for the reply.
I forgot to mention that I also replaced the entire head since I could not get the screws out of the feathering shaft to replace the shaft on the old head. So I'll double check but I don't think the head is cracked.

Also I had a 2g tail before that worked fine. I think this 2g tail has enough power because when I turn up the gyro gain the tail heli starts to gradually turn to the right, but when I turn the gyro gain down it starts to gradually turn left.

I would have gotten the 2.9g tail but at the time I didn't want to have to buy a new tail holder to fit the 2.9g tail.

[Dusty1000]

The vibrations will be playing havoc with the gyro, and that's why the tail is misbehaving.

When you replaced the head, did you replace the main shaft as well?
Did you balance the blades with tape?

Like SQRT says, the 2.9g motor is well worth the extra, won't fix your current problem though would be worth ordering for the (near) future

Dusty

[mikejbb]

On mine when the tail stand was vibrating, the culprit was the tail boom. Even though it doesn't show, you probably have a splintered cf boom. You can temp ca all 4 sides, but you'll have to replace it. After replacing my boom, the tail vibrations were gone. I then added "struts" made from strips of the broken tail boom and ca'd 2 of them from the body edges to about 2" from the tail. I did the thread wrap where they connected to the boom for better strength and that connection never broke. But the body connections break off easily, but while they are on, the tail works much better and you can turn up the gyro gain so the tail will hold in full throttle spikes. I do have the 2.9g and it is wonderful. I even used a square aluminum boom while I was waiting for my ordered replacements. I then had to turn down the gain since the aluminum I used wasn't even close to as stiff as the stock cf boom.

Regarding vibrations, do make sure the head is balanced by watching the blade grip screws to be sure they spin in a circle and the blades are in line. I found my head was out of balance without the blades on and so I added a small piece of wire to one grip to get the head spinning without vibrations (mostly). There's probably some better way to do it, but that works. And then turn up the gyro gain cause you can.

[OmegaRedIsDMan]

Originally Posted by mikejbb

Regarding vibrations, do make sure the head is balanced by watching the blade grip screws to be sure they spin in a circle and the blades are in line.

Thanks to everyone who replied. It turns out that the pre-assembled walker metal head kit that I had installed was assembled with an extra washer between the head and the blade grip on only ONE side. The washer was so small that I didn't even notice until I took off the blades and watched the head spin. I took the blade grips off and removed the washer. I also turned around the stepped washers so that the smallest part is against the head. Now the heli. is flying much better. It's hard to believe that just that small washer could cause so much trouble

Thanks again!
-DMan

[Ampdraw]

Great you got it sorted...any vibes and the tail goes nuts as you found out!

Re the little stepped washer. The small side should go facing the grip. It is a smaller diameter so that it only contacts the inner race of the grip bearing and allows the bearing to work correctly.

Amp

[OmegaRedIsDMan]

Originally Posted by Ampdraw

Great you got it sorted...any vibes and the tail goes nuts as you found out!

Re the little stepped washer. The small side should go facing the grip. It is a smaller diameter so that it only contacts the inner race of the grip bearing and allows the bearing to work correctly.

Amp

well I turned the stepped washers around based on the info from this thread
https://www.helifreak.com/showthread.php?t=161753

there seems to be some belief that it is more stable when set up this way. So far it seems to work well.

-DMan

[SQRT(-2)]

Also, don't forget to balance the blades, a tiny bit of tape can make a large difference.