I just rebuilt my t-rex 450, I've been working on this for about 2 weeks chasing whatever is making the tail shake, I just can't figure it out...

I've replaced:
main shaft
tail shaft
front pulley for tail
rear pulley for tail
flybar
main gear
feathering shaft
blades
flybar paddles

just about everything I can think of, I even took the tail apart to make sure the belt wasn't crossed, yet I can't figure out what has gone wrong... does anyone have any good ideas?

have you looked for broken servo gears

servo's all feel good, nothing is twitching or anything...

is it possible that I have the tail stabilizer too tight and the vibrations are being amplified? it seems to fly fairly well, I haven't flown it much yet because of the shake..

do any of the tail links have slop? maybe a bad ball link or something?

The best thing you can do is just go from servo to tail blades goining through every part and checking it until you find something wierd.

Take a look at your tail blade grips to make sure they are tight as well as the picth slider ball. On my V2 that gets loose quickly.

Is the tail shaking up and down OR side to side?? What gyro/servo combination???

Up and down is usually a blade imbalance.
Side to side could be gain, low headspeed, too tight/loose belt...etc.

Tailblades must swing freely (but not too freely) ... they should NEVER be tight in the grips.

when i got my 500 it was doing the same we had to turn up the head speed and it went away it was really weard

aarrrghhhh!! guys, this is just frustrating...

ok, I had it apart last night again (have yet to try to fly it, just don't want to go back into that depression, lol) it seems that the vibration is coming from the main chassis and just showing in the tail (you know what I mean?)

I don't have any slop that I can find... I'll check the belt tension and blade grips and then go out and try it and see what happens.

the gyro is a 401, the servo is a hitec... this came directly from the flying t-rex and onto this chassis, I wouldn't think that I'd need to change the gain right? (I will just to find out) seems like it's more of a side to side shake, I'll verify that also in a minute.

the headspeed? I went to a lighter chassis, but everything else remains the same, should the headspeed changed?

ok, I went and flew it, the tail still shakes but now not as bad (maybe 1mm of movement, side to side, at the bottom of the tail stabilizer fin in flight) I think this is tolerable...

I'm also thinking my main gear may be a bit out of round, I'm going to replace them as soon as I get a chance and see if that helps.

Have you had the head tached?

Are you sure your flybar/paddles are in balance?

What I do when setting it up: Insert the flybar rod and measure to the exact center, and THEN I'll see if it balances by watching it teeter on the mast. (NOTE, I do this with the cage links dangling and NOT connected to the mixing arms). Tighten the rod to the cage.

I then apply the weights if desired and temporarily slide them in towards the cage. From there I'll screw on the paddles at the same distance out from the cage, Then I'll check to see if it balances (teeters evenly on the mast).

Slide your weights out to the desired distance then check the balance ONE MORE TIME. Finally you can connect the cage links to the mixing arms and you're good to go.
BTW, I balance my tail blades too. EVERY Rex heli I own has virtually NO shake/vibes. FWIW, if it spins... balance it.

Good luck

thanks man, I'll check it all out one more time, it don't seem that it shook this bad in the XL chassis, but now taht I put tthe HDX450 chassis on it, it's got the shakes.

I'm thinking maybe that lower main gear or the autorotation shaft also... I'm going to swap them out and from there I'll keep looking...

normally, this is fun for me (finding problems), now it's gone on too long and has become a frustration... I've thought and though about it, and now both of my brain cells are too tired to think anymore


oh yeah, I'll throw the tach to the head also.

when I put the flybar in, I just measured it even, I'll try your route and see if I can get the change there.

Strato',

A majority of the time I DO see a difference between measuring and static balancing, this is my experience with all types and brands helis (helping the club's student's helis and my own).

You'll get it bro.

Peace

thanks bud.....

when I get off of work in the morning, I'll rebalance the flybar doing it your way, then I'll run it outside and tach it just for giggles and then see how it flies..

I'll let you know what happens...

ok, I measured the flybar, cage, rotor housing, everything possible, and that sucker is as center as it'll ever get.. then I balanced everything, put it together into an old chassis and made sure it stayed balanced, it spins like a dream. Along with that, I changed the tail belt (it was the only thing left that hadn't been changed) removed that tail pulley and went through everything agin. I also found that my rudder servo had a broken tab on it, so I replaced the servo, but this could've very well been the problem, it was a bit free...

oh yeah, I tach'd my headspeed, without blades, it came out to 2790 rpm, is this fairly decent? I didn't do idle up, it was raining..

we'll see what happens when the rain clears...

man this is flippin' crazy!!! everything on this heli is new except the reciever, and flippin' battery!

I took her for a test flight today, came off the ground pretty decent, I flew it around, made a left turn, FF, right turn, then it decided to shake itself afreakin'part!! It shook, the canopy got beat off, then hit by the rotor blades, I landed it and brought it home. I look at it, the mainshaft is bent all to hell, and this was without a crash, the mainshaft is bent, it was straight before the flight, what the hell bends the shaft in mid flight?

that sucks man, there's something very wrong with that heli, its gone MAD[>:] that all that was wrong with it
The only suspect left is the receiver, but as you said how's that gonna bend the mainshaft, damm!

I've angered the heli gods

I have no clue now... it's coming all apart and I'm going to start the rebuild entirely again.... I may leave the motor on the chassis, but that's going to be it! <insert string of sensless obscenities being muttered here>





maybe I should take up vodoo to help me out with flying? start sacrificing small animals? hmmm....

anyone know a good witch doctor? maybe I'll start a thread about that...

hehe! maybe you should get in contact with koolaid535, his heli flew itself between buildings and then landed, now that's madness!

I couldn't find a witchdoctor in the yellow pages so last night I sacrificed a bug to the heli gods, thinking that wasn't enough I looked at co-workers but decided better of it

I did look at the heli last night, it seems one of the servo's had come loose, I'm assuming at this point it gave way to the swash which bent that shaft... at any rate, a new high carbon shaft went in, those cheap ones all seemed bent... I thought about it and decided I didn't like the way my linkages looked and the setup, so I flipped the servo's... this allowed me to shorten the linkages (made me more comfortable not having them as far out on the threads), I checked everything over again and took it outside...

I got it up into a hover, no big tail shake, it did hover better than I ever remember it hovering, I'll try sacrificing another critter and flying it again this afternoon..