Bad vibration

[UAV_PILOT]

I got a bad vibration once I get to a hover. The tail starts shaking and sounds real rough. Also the skids vibrate so bad they look fuzzy. Any ideas what it could be?? I was thinking maybe a to tight of a tail belt.

[Blue-Heli]

A few months ago, I had real bad vibration with my heli. The tail vibrated up and down real fast and the landing gear also vibrated real hard which to the point it looked fuzzy. The problem began after I had a crash with it and I had to replace the main shaft and the feathering shaft. After lengthy investigation I noticed the Metal Main Rotor Head assembly did not fit snugly to the main shaft. At first I did not think it would cause any problem since I tight the socket screw (many people call it Jesus bolt; see page 5 on T-Rex 450SE v2 instruction manual page 5 right in the middle of the page) real good to the nut. To make it fit snuggly to the main shaft, I used a vice grip plier to squeezed the casing at the bottom of the Metal Main Rotor Head assembly very carefully a little bit at a time. After that the vibration went away.

If you have the chance, please check if you have similar issue like I had as I described above. I must warn you in advance though that you have to be very careful when squeezing the casing at the bottom of the Metal Main Rotor Head assembly. If you make it too tight, you might ruin it and you may have to replace it with a new one.

[UAV_PILOT]

Wow I didn't think about that! Thanks, I will check it out. This whole time though I have been having a problem with my tailboom sliding out and making the belt too tight.

[outhouse]

Originally Posted by UAV_PILOT

I got a bad vibration once I get to a hover. The tail starts shaking and sounds real rough. Any ideas what it could be?? I was thinking maybe a to tight of a tail belt.

not to tight a belt that wont do it.

belts normaly do not tighten themselves up, they loosen.

pull mainblades and tail blades off and spool it up and search for your bad vibes

[UAV_PILOT]

Well I think I may have a bent main shaft, which is wierd because I have not crashed yet?

[Andy01]

Easy enough to check - just roll you shafts on a piece of glass.

Colin

[UAV_PILOT]

Yup sure was bent.

[rcjpth]

Originally Posted by UAV_PILOT

Yup sure was bent.

uhmmm you don't crash - how could it be bent? I remember I read some thread around here, there are some self resistance from the material of the shaft during the high load that couldn't get the mainshaft back to its original shape...etc. It's kinda mystery but it does happen for someone as I heard of.

tks
rcjpth

[jteee]

Originally Posted by rcjpth

uhmmm you don't crash - how could it be bent?

It's not too uncommon to put on a new main shaft only to have it bent when checking tracking.
I've pulled new Align's and aftermarket Hong Kong shafts that were bent.
The only good thing is that when paying $1.00 per shaft, it doesn't hurt the wallet too bad.

[UAV_PILOT]

Also the tailboom support rods keep coming apart from the metal that screws into the frame and when that happens I get a bad vibration as well, like those supports HAVE to be on there.

[latte]

I wonder if I really need the boom-support with the alu-tailboom. A discussion I read a while back, had few facts about it, but the conclusion was that if your doing slammering 3D, you might want that extra stiffness.

What do you think? (Reason I ask, is because I have slight vibration also, and the supports always come loose)

[Andy01]

Good question - my Atom 500 does not have support struts, but it has a huge boom for a 500 - about 20mm diameter.

On HeliGuy forums there is a recent thread about a boom on a 450 shearing off just behind the boom block. The only thing the guy could think of was that his struts were a bit loose and it had fatigued and broken in flight. He has pics - the boom is not bent at all - just a clean break.

So I would say that the answer for a 450 is yes.

Colin

[latte]

I have also had a clean break right behind the boom, with a carbonfiber boom. Never ever using that again. My spare CF boom was also manufactured too small, the original Align ones.

In the end, all materials, especially brittle ones like aluminium, will fatigue from vibration. But I have tried everything. Rebuild it several times over. But I got a tip from this tread, to try to tighten the metal rotor housing, as thats the only thing left.

[Wolfpackin]

IMO, the tail boom supports definately provide structural support to the boom and prevent it from flexing.

CF might be better but I'd still use the supports.

[UAV_PILOT]

Well right after I got the boom supports fixed I was doing some light 3D and then crashed it! Dang! I just fixed it too! I was doing a front flip with a piro and lost orentation and gave it the wrong pitch and SMACK! This is one tough bird though! The only thing I have to replace is the blades, main shaft, and main gear.