kinetic 50/head wobble

[kiptone]

can anyone tell me where i can get a better fitting head/yoke for this.i had tower hobbies send be another new piece,but there still is an off center condition in the head.i have checked the shaft,its true.and will any other upgrade parts fit this...this is a kenetic 50/with 10mm main shaft,,,

[GyroAl]

Have you tried to fly it? That is the true test.

If it does not vibrate - then the bloke is OK as there will be a number of things that can cause an illusion to a wabble on the bench.

[kiptone]

i have not tried to fly it ,because it really shakes on spool up,,,even with the mains off.i am goingb to take the head back off and recheck the main shaft,,its never been flown yet,iam sure the shaft is true,but iam going to check again.i'm sure the head block is not true,,it's only plastic. i would like to find a cnc head block for it,,,any sources that you know of?

[RAV50]

There are literally 10's of thousands of Hawks that are using that same head block and all fly well.

If you have a shake I would suspect it is something else (flybar balance or maybe a bent mainshaft???)

Of note, is when spooling up ANY helicopter you will get some shaking until the mainblades find their natural lead / lag.

But if you want to buy some BLING, you could get a complete metal head for it:

http://www.heli-world.com/detail.aspx?ID=8759

or assemble a Raven head using the parts differences between yours and the Ravens'. I believe you both use the same flybar/paddles and the same blade grips and feathering spindle arrangement, so you would have to change to the CNC head block from the Raven and the seesaw system from the Raven.

You can see the different parts by downloading the Raven 50 manual that you sill find in the customer support area of the Century site.

http://www.centuryheli.com/support/manuals/RAVN_30-50V2MnlBkltEdtn3.pdf

[t2o]

Hello,
I am new here and new to the heli thing... so I don't have a clue what I am talking about.
I learned to hover with a Honey bee FP and then a Blade 400. I am just starting forward flight and can hover all the way around the clock. I got nitro fever and bought the Kinetic 50. OK so you know where I am coming from.

I did not completely disassemble and rebuild the entire Kinetic before I flew it. This produced my first crash when the tail coupler came loose because of no loc-tite. I could not get parts for the weekend so I bought an entirely new kit and robbed the parts I needed. (I replaced the main shaft and everything above the wash-out, also the tail boom & shaft) Ever since, I have had a wobble from the head just like kiptone. I have balanced the blades so many times I have lost count and still get a big vibration. My dealer, who is an excellent pilot, has suggested that maybe the thrust bearings are not installed in the right order. He says that while the races look almost the same there is differance between them. It seems possible, that if they forget to use loc-tite on every set screw in the tail drive, they might have these installed wrong. I will know tomorrow and report back. I will say though, that it does indeed look like the whole head wobbles!

[kiptone]

I took the head apart,and found main shaft not machined correctly,have one comeing,,will let you know,,,note;if this shakes enough,will it cause the electronics to do funny things???like the gyro,or what ever?

[GyroAl]

Wobble - do you mean a low frequency bobbing or a vibration?

If it a left/right or fore aft bobbing that is always the result of flying at too low a rotoe speed for the damping hardness of the rotor dampers.

[t2o]

Hello,
The thrust bearings are correct on mine so thats not it.

It looks like a very small wobble when on the bench, Maybe a couple of thousanths off, and this becomes a big vibe at hover speed. The tail looks blurry, the body shakes it ain't pretty.

[RAV50]

t2o

It flew smoothly before your crash so it is directly related to your repair after the crash.

What parts did you replace?

[t2o]

Hello rav50

I replaced the main shaft, flybar, rotorhead (complete from the new kit), blades (all of them), tail boom, tail drive shaft and main gear. Only the swash and washout remain, they are perfect. After the crash I simply replaced everything from the washout up with a new unit from the kit I purchased as a spare.

Today I completely disassemled the head looking for anything, but found nothing. I am waiting for a balancer so I can try balancing the hole assembly. The guys at Tower said that perhaps the rotor head yoke was a bad cast, I checked it out real good and it is identical to the old one.

Tower is sending me a another shaft but tomorrow I will try it again with what I have.

The funny thing about it is how well the gy401 works even when being shaken to death. The thing is rock steady!

[RAV50]

If it is a high frequency vibration, then it is engine related - as it was smooth before and you changed nothing in that area, I would only suspect that maybe the engine is too lean or you lost some fan blades in the crash.(e.g. a good indication of these problems is that your fuel in the tank will tend to foam)

If it is low frequency shake, then it is something in the head so maybe your main shaft is bent, your flybar is of center or off balance or your main blades are off balance. (usually indicated by shaking landing gear skids)

If it is a mid frequency vibration, then it is tail rotor related. This is usually the result of an imbalanced tail rotor - one blade grip coming loose, a bolt holding one or both into the hub is bent, or the tail rotor output shaft is bent. (usually indicated by vibrations at the tips of the horizontal fin or bottom of the vertical fin)

A real LOW frequency wobble is almost always the result of too low a rotor speed.

[t2o]

Sorry about taking so long to get back, it is always crazy here!

The vibe is low frequency so I stayed focused on the head block. I re-read Rays Authoritative Helocopter Maunual Chapter 20, measuered the blade grips and found them un-equal from the center line of the main shaft. I had to set up and measure from a point external to the heli because the wobble seems to originate at the head block. I figured measuring from the center of the head block would be useless if it, in fact, was the root of the problem. According to Ray's manual this is not uncommon with plastic head blocks and he recommends shimming the short grip out untill they are equal and then rebalance the hole head, cordwise and spanwise. The distance here is about .5 mm and I have found a washer that should work for this. My balancer will be here by the weekend and I hope to have this resovled soon. Thanks for the help.

One other thing, do you know if the Raven CNC head block will fit the K50?

[RAV50]

Yes the Raven 50 Head block will fit the K50, but you will also have to change to the Raven 50 seesaw system which is from the Century Predator 90.

Check the Raven manual on the Century web site (in the customer support area icon) and you will see the different parts you would need for this.

[t2o]

I think I will start looking for a used Raven!

[RAV50]

Could be hard to find a used one. Most I know, once they get one, don't want to part with it :-)

[t2o]

Rav50
What you say is true. There is about nothing, zero, zippo on ebay for Ravens. I am persistent, however, and if one shows up I will know.

I have measured 4 K50 main blocks (called a yoke in the manual) part number hmxe4466 http://manuals.hobbico.com/hmx/hmxe0250-manual-v1_1.pdf pg39, and every one spins un-true one of them was out by over 1mm. Simply balancing the blades will not get rid of that vibration. I flew today for a bit but it was too windy for my unsteady thumbs to deal with and I had to give up. I used the washer from a glow plug as the shim to get the blade grips even on both sides, this was a major improvment. It is still shaking a little but the improvement was such that I know I am on the right track.

[centuryman]

Why buy a used raven when you can get a new one for $270.00 from tower hobbies?As for the cnc headblock don't get the raven one. get the upgrade full cnc headblock for $32.00 and the seesaw is the same as your kinetic. I've upgraded my whole fleet to this headblock.Bolts right on to the hawks and kinetics.I also upgraded my 3 ravens to it,but on theme i had to get the kinetic seesaw pivot to make theme work.

[t2o]

Thanks Century Man I just ordered one.

As for the why buy used question? I would not, of course, pay more than what it is worth and sometimes I get lucky indeed!

I

[t2o]

I got the aluminum block, Century part # CN2556 installed a few days ago and just like magic all the vibe is gone. This upgrade has fixed the Wobble of Doom! Now I can fly without fear of my heli shaking parts off itself.