My 700 vibrates like hell :(

[loiphin]

Hey all,

I am still having teething problems with my 700. Its the first 90 size heli I have owned and I can't get used to how much this things vibrates compared with my 600N. The heli flies fine, but I think I am suffering from premature mechanical failure because it vibes so damn much.

1. First thing to happen (after two flights) was the exhaust end fell off (MP5 - prob bad solder). Replaced with a Hatori #939.

2. Carbon spar that supports the boom came loose at the frame end. As I landed the spar bent backwards and got chewed up by the tail rotor. My fault for not properly loctiteing.

3. Nipple in my Hatori pipe has vibrated loose and destroyed the threads in the muffler. So I have to retap with a 5mm, plug the hole, and drill new 4mm hole and tap for the nipple.

4. And finally the rear engine bearing has gone bad, after only 10-15 flights.


I am sure the replaced bearing will help matters with vibration, but still it vibrates such a lot and the poor heli shakes itself to bits.


loiphin.

[HeliSmith]

Sounds like it could have been the motor bearings from the start. Change them and see if the vibration is gone make sure to get good stainless bearings. Otherwise time to start checking the usual suspects.

Vibration is bad you shouldn't fly with it. Mine doesn't vibrate and honestly I didn't even balance the fan it seemed ok. I aligned my frames very carefully square then tightening the screws on the second side. Using a mainshaft to make sure it slides through easily. Sometimes you have to loosen the clutch stack and tighten it again.

[stevehonn]

The MP5 has been withdrawn from sale due to failures similar to yours so this could be down to a component issue.

I've had the boom support vibrate loose, exactly the same as yours. I've since refixed it using some green Loctite. I've seen a few people report this with helis that weren't vibrating significantly.

The rear bearing could well be a major factor.

I get a lot of foaming in my tank which is normally seen as indicating a vibration issue but the 700 does seem to foam the fuel almost come what may, some blame pressure feed, others tank rubbers too tight.

[scooby61]

same problem here but i've seen many 7s that don't foam. i'm running the ys and a t first it foamed real bad found out i had the tourqe tube in too tight causing the shaft to cavitate. after dissassembleing the heli again and fixing that issue it still foams just not as bad. think i may shotgun it and replace most driveline components i.e, main shaft, clutch assy., fan , and main gear, this problem is driving me nuts.

[Laurens]

The MP5 has been withdrawn from sale due to failures similar to yours so this could be down to a component issue.

I never heard of that and I can't find any information about it on the CY website. Where did you read this?

[Rototerrier]

I had this EXACT problem with my 600, with the boom supports vibrating until they broke off.

Turned out it was a slightly warped Torque Tube. I purchases a Dubro TruSpin and spun and bent and spun and bent and spun....etc... I ordered a new one and it was bent too. I was eventually able to get it perfectly straight and now my 600 is vib free. Have not had the issue with my 700, BUT I did put it on the TruSpin during the build and it was perfectly straight. Just something to consider.

[Gearswinger]

I never heard of that and I can't find any information about it on the CY website. Where did you read this?

Call them and ask them. They aren't making them anymore after having failures. I tried to get one a couple months ago and that's exactly what they said. I ended up buying the Hatori instead, even though I HATE spending that much on an exhaust.

[loiphin]

Hi All,

QUICK UPDATE -

I replaced the rear crankshaft bearing on my OS 91 SZ-H PS and its made an enormous difference. It really flies smoothly now. Very pleased! Finally, after having the heli for months, it now feels right. :) :) :)

loiphin.

[John Cook]

I'm going to buy my wife an OS SZ for X-mas :whip:smokin::YeaBaby:

[DesertFlyer]

My 700 with YS91 vibrates pretty bad too. I'm even getting some noise now. Someone told me today that they use a dial indicator to properly align their fan and clutch. Is that necessary?

[HeliSmith]

What kind of noise like a can full of nails? Rarely have I seen a vibration that was accompanied by a noise.

[Rototerrier]

My 700 with YS91 vibrates pretty bad too. I'm even getting some noise now. Someone told me today that they use a dial indicator to properly align their fan and clutch. Is that necessary?

A dial indicator would only be helpful to determine if the shaft is bent or the fan hub is out of round/defective. If either is the case, the only thing you can do is replace the parts. I would not find it out of the realm of possibilities, but I would save this for the last resort...unless you just have a dial indicator you can use or borrow.

Take the head off and fire up the engine. See if it vibrates the airframe. Process of elimination. If not, then you know to look at the head or tail. Good luck