Vibration while spinning up

[darinr80]

I have a stock 550E 3G I fly w/a DX7SE. I have not done any mods. For some reason, when I'm spooling up, the heli vibrates and does a little dance which always makes me a little nervous so I mess w/the cyclic slightly, then pop it up in the air ASAP and let it finish spinning up. I always fly in idle up 2 at 100%.

[GT86]

You'll usually get some vibration as the head is spooling up until the blades straighten out. And at lower RPM there may be a resonance going on that disappears as the RPM increases.

You may also have a vibration source somewhere that's more noticeable on the ground.

[darinr80]

Thank you. On that note I wonder if my main blades are tight/loose enough to the blade grips. Not sure how to tell.

As well I have heard that there might just be some awkward ground effects from the 3G sensor (trying to compensate).

[Fullonoob]

You might want to go over your head setup again, one of my swash link was out 2mm. now no more vibration

[khymlawrence]

my first flight had a little vibration also, dance on skids also but after i put brace on my tail fin and made my throttle curve 0-70-100 on normal, the vibe is gone, i think its just headspeed. my 3g sensor has 1 align mount and strapped on the rotation bracket. settings all on 10 o'clock.. went up fine now.. my mainblades and tail blades are not tight so the can straighten in spool up.. read it somewhere..try headspeed ang blades tightness i think. ..

[darinr80]

Thank you. I will try loosening the main blades. I should say I replaced the tail fin w/ the 600 size 2mm to eliminate vibration in idle up 2.

[Wolfpackin]

If the blades fall under their own weight then they are way too loose, IMO.
I run them pretty tight and never had issues.

[bedye4]

I have a 550 3g as well and just recently was able to fix the vibe that I had at a funfly. If this is your first flybarless helicopter you should know that while spooling up you dont need to give any cyclic input (regardless of wind, incline, etc). The 3g works just like heading hold, you give a small input and it will adjust the travel depending on the response it is sensing. so if the blades are not up to speed and you are giving input, the 3g will overreact and give large swash movements because it is not sensing any movement. once this happens it will begin to go into a circle type dance unless you throttle hold. on takeoff I reccomend flipping right into idle up with the pitch slightly below mid stick so the heli stays glued to the ground but is able to get the blades rockin, and give no cyclic input until the blades are up to speed. The 3g will make adjustments as the blades are coming up to speed and keep it level.

If this is not the case I have a few more suggestions....

for one, I found some benefit in the 3g mod. you use nonconductive silicone adhesive and it helps reduce the vibration inside the sensor. you can find the info in another thread either in the 550 category or in the 3g category.

whether you choose to do the mod or not, what really reduced my vibe was moving the sensor down to the bottom plate. A lot of people have said to "hard mount" the sensor to the bottom after the mod however this made my heli go ballistic. Instead i switched to the soft gyro tape that came with my spartan gyro and the vibe was gone.

hopefully this helps!! does the heli do the wild dance once you have it in the air? is it jittery at all?

[khymlawrence]

YouTube

YouTube

heres my maiden with my t550 with reduced to minimum wag and bob. for me i found it negligible already.. all stock. only blades loosen from hand tight and back the screw 3/4 of a turn.

[Raptorg2zman]

I also have a question about spin up vibration although I suspect I already know the answer. Went to maiden my 550 yesturday after re-setting up the head. Everthing level & set up right by a friend who set his up. Anyway I have the 3G sensor on the anit-rotation bracket. after several failed atttempts to fly I noticed I fialed to put back the canopy mounts on the anti rotation bracket. I'm guessing this is probably most if not all of my issue.
I would be interested in feedback

[darinr80]

So I learned a few things. First, I adjusted both my blade grips to be a little more tight, and in doing so I noticed that one was already more tight than the other, which I heard can cause vibration. Second, while it is spooling up, someone said to not give it any negative collective and because I only fly in idle up 2 at 100%, to keep my collective at center then give it positive so it gets up as soon as there is enough lift. Both of these helped a little, but I still noticed some vibration from the head so the skids wobble a little.

Lastly, a guy at my field flies the same bird, but he did the Leon Luke 3G mod to the 3G sensor and his didn't vibrate. He swears this is the answer...

[reyn3545]

I spun my 550E up for the first time today also.. I went with a Skookum SK720 flybarless system on it.

I had the same blade shakes while spooling up... and down. I think it may be the blade tightness, althouth I tried to keep them pretty even. As a rule of thumb... they should NOT fall under their own weight... correct?

[Wolfpackin]

Correct, IMO.

I make them a little on the tight side but still smooth when holding the grip and pivoting. I straighten them by pulling on the tips and sighting down the blades to get them as straight as possible before spooling up.
I never have a problem with vibrations doing it this way.

Balancing and tracking is also very important to reduce vibration.

[reyn3545]

That was it! Tightened them up a little, spun up very smoothly. Blade tracking looks very flat.... time to get this thing off the ground!

I did have to put a lot more weight (tape) than I would like in order to get them properly balanced. To get the CG right, one blade needed one of the foiled strips right out on the tip... I was going to put one there anyway. But then, in order to properly balance, I needed 2 of the large foiled strips and 2 of the smaller strips right on the CG location of the other blade. As long as the tracking looks good, I'll stay with it, but it's a lot more tape than I thought I should have added.

[darinr80]

Yes that is correct. My blades may be too tight but I just checked them. I need to take a video to show you guys what mine does. Some say it is resonance but it seems worse than other helicopters at my field.

[darinr80]

To make this even more awesome, the guys I fly with said it was resonance, and some disagreed saying no it looks way worse than that!