Vibration - tank foaming

[Aviation addict]

Guys,

I've flown that pants of my machines this summer and they are now foaming the tank a bit. On close inspection is seems that there is play in the mast bearings so I've changed them for new which has made the mainshaft solid again.

I've also greased the 'main blade' and 'tail' thrust bearings again. Due to a 2 week event at our field I've been unable to see whether these changes have made any difference.

Has anyone else been through this senario and regained the smooth machines they once had done the above?

If they are still foaming the tank (usually just the top 1/3rd) I'll check the run-out on the starter shaft again, but when it went in it was Zero.

Q. Can tired old mast bearings and/or dryish thrust bearings induce significant vibrations?

Cheers,

[Chuckie]

I suggest you also check to make sure the TT is installed straight on the tail box. Put the box in a vice with the TT pointing up and slowly turn the output shaft. If the top of the TT moves beyond 0.5inch then you might be getting vibrations from the TT. Readjust the 4 3mm set screws to center the TT.

Q. Can tired old mast bearings and/or dryish thrust bearings induce significant vibrations?

Usually the grips will lock so pitch might not change and the heil will be hard to hover. I don't believe they will cause vibrations.

Also, check the tail hub and tail output shaft. They might not be straight and they will cause vibrations in the tank.

What motor do you have?

Charles

[Aviation addict]

Hi Charles,

Thanks for your suggestion there. I'm running the Hyperdrive on one heli and the standard (but pinned for peace of mind) tail drive on the other. Will certainly have a good look at the tail drive and associated bearings.

Am using the YS91 SR with a CSM carbsmart maintaining 100 degrees. I don't think its the bearings. Engine sounds sweet enough. May as I say whip her out and dial the starter shaft on a rainly day to see that the runout is still minimal. Don't like to see any more than 0.001".

[Chuckie]

My SR was also shaking the heli a bit and I found after 120 flights I needed a new main bearing. Also, changing the plug helped reduce engine vibrations.

Charles

[Aviation addict]

Going to change out all tail bearbox beaings. Noticed that a couple had been moving ever so slightly in the gearbox. Going to red loctite the new ones in or use bearing lock.

Also going to replace the starter and clutch bell bearings. They probably take some hammering.

That should smooth her out, I hope.

Have a mate with a Synergy and SR and his fuel tank is like a mill pond even with a full tank and at 1900rpm +. Will home in on my vib issue sooner or later. Hope to test fly it early next week.

[Aviation addict]

Prior to test flying after all the changes, I got up the motivation to remove the engine and dial guage it. Found it to be 0.001". I therefore put her back in again. This time I got help from my buddy with aligning the engine - and ended up putting more shims in than before to get the main gear meshing right.

Took her to the field and...... she sounded smoother at idle. No vib's coming through the heli as I carried it out. Spooled her up and at 1900 rpm she foamed the tank again (plus the gyro slowly drifted left).

At about 1/2 tank contents the fuel is nice and smooth. Gyro still drifts slowly left though.

Q. Can the GY611 servos (S9256) get tired at all, or do they work perfectly then one day fail? Just wondered if its time to put a new one in there. The present one has had a lot of use.

Think I'll just have to get out there and fly it. Not sure that I'm going to get her to stop foaming the first half of the tank. Bit disappointing after all the work. Despite the back bearing being less than a month old, it could be causing the vibs. Will keep a good eye and ear on it.

What a hobby. Must take up golf!

[Chuckie]

Well sorry to say but the fact that the gyro is drifting tells me there is too much vibration from somewhere.

Charles

[david.read]

What a hobby. Must take up golf!

Thats what i did....

David

[Aviation addict]

Hi David hope you're well. Golf is without a doubt the best option for the wallet, your fitness and sanity! Should follow your lead.

As for this machine, to date, its never been crashed (from new) but continues to foam the first half of the tank. Tried to balance the tail rotor today. - tail hub complete with blades. Need to try it now.

[Chuckie]

Just fly the Fning thing!

[DavidH]

Just fly the Fning thing!

I agree, That way he can find out what is causing the vibration. LOL

David

[Aviation addict]

I am flying the F'ing thing. Sorry to have bothered you.

[X]

Aviation addict, did you find out what cause the tail drifting?

This is my second Synergy and only ran closed to 20 tanks. Tail drifting to the left also. Using 601, YS SR, all hypers. Still can not find my problem. Any input would be appreciate.

Thanks,

[tec548]

Mine did that for a while. Turned out to be the bearings on the tail input and out put shafts.

Joel

[Robgunbuilder]

I just finished building my first Synergy and flew it yesterday. It flies great but shakes the tank considerably. One thing I did discover was that the clutch had significant run-out. I held the rear of the clutch in my Lathe( it has enough of a round boss to grab in my 6 jaw) and measured the run out at approx where the bearings are positioned and it was .050. Another one was .200!
A friend who is also building a Synergy has seen the same problem with two other clutches.
Since the shafts are just press fit into the hardened clutch, The shaft can be straightened a bit but I was unable to achieve better than .004 run-out . My guess is the clutch itself was drilled, slotted and then hardened which caused some slight warpage which is amplified at the end of the shaft.
I don't know if we got a bad batch of clutches or what, I don't think a press fit shaft is the right way to go. At a minimum they should be threaded and llocktighted. I deceided to try my straightened clutch and still saw foaming in the tank. The motor itself runs smoothly and doesn't shake appreciably. I'm going to make a new clutch assembly myself, thread it and the shaft and see what happens with a zero runout assembly.-rob

[Chuckie]

Rob,

I have not checked the clutches like you describe as it doesn't matter if the bottom edge of the clutch is not straight. I dial indicate the base of the clutch shaft when I install it to the hub (after dialing the hub as well). In one clutch I had to open the 4mm screw holes so it would give me enough room to position the clutch shaft with zero runout.

Then I checked the runout at the top of the shaft just below the hex starter adapter hole. I used the closed end of a wrench placed it as low as it would fit on the shaft and bent the shaft to get a low runout at the top of the shaft. It took a few tweaks to get the shaft to dial straight through most of its length.

Thought I don't know how much it can be off to cause a problem I would think it’s good to have the side of the clutch (what contacts the bell liner) and base of the clutch shaft match. I can't tell how well they match because the clutch shoes don't allow an accurate dial check of the clutch side after the shaft is dialed straight on the hub. Also once the clutch shoes move out and lock the bell the entire assembly balance and runout is affected.

If you think the engine and clutch are set correctly then the next place to look is the TT. As I mentioned before in this thread you should also check the runout of the Torque Tube onto the tail box. You need to make sure the TT is straight and cannot just tighten the 4 3mm set screws in any order. Dial indicating the top of the TT shaft is not necessary just put the tail box in a soft vice so the TT is pointed straight up and slowly rotate the tail box output shaft. The TT end should not move more than 0.5 to 0.75inch.

Regards,

Charles

[Robgunbuilder]

Chuckie- Thank you for the thoughtfull reply. I will have to drop the motor and recheck things in a few days. I have the Hyper hub and Hyper drive torque tube assembly and run out on the tail looks good. Even with the clutch shaft having.004 runout, when I rotate the starter shaft by hand, I can see the clutch bell wobble. The back ridge of the clutch fits right into the hyper hub so there really isn't much adjustment possible. Once the engine is running at idle though I can't see this wobble anymore. At this point the clutch is not engaged and I expected to see the engine vibrating . To my amazement I could not feel any vibrations in the engine. The fuel in the tank shakes pretty well although the gyro is doing fine. I will check the TT though and see if ther is anything else going on. I really don't like the idea of trying to bend a press fit shaft. It definately loosened when I tried and it would not take much for the starter shaft to spin right up and out of the clutch. I purple locktighted the shaft in an attempt to keep that from hapening. In aheli of this high quality, I'm pretty disappointed in the way this clutch assembly is designed and or manufactured. -Rob