weird vibration issue

[therick04pp]

Hi all,

So I need a little help with this. I replaced all the plastic head components with aluminum upgrades from Microheli. I replaced eveything because I was having this vibration issue I couldn't pin down after replacing all the moving parts, but it has continued even after replacing EVERYTHING on the head (including main shaft, main gear).

SOMETIMES* this happens and other times it is so/so. Sometimes around 25% throttle, sometimes when I am at about 40/50% throttle and only a few feet from the ground. The heli will start to wobble badly. I cut throttle and land. Take off again and it goes away. It is intermittent and comes and goes without me having to do anything except land and take off again? Sometimes the blades track perfect and sometimes I see a slight variation. If I hold it in my hand, I can feel a vibration at a certain lower stick throttle but seems to clear up a bit at higher RPM.

I have balanced and obtained correct COG on my blades and everything feels good on the head (no play or slop). Flybar paddles track perfect as do the weights and flybar itself. placed the servos on my tester and ran them (auto cycle) for a while, no issues there. Even when the blades are tracking perfect, I can feel this vibration at lower throttle. Bad at first and then it clear up a little making it so i can fly above 5-6 feet. If i try and hover lower (lower RPM) the damn thing looks like it is going to wobble itself out of the sky... SOMETIMES... lol

Anyone have any ideas. i'm all out?

[nighttrain06]

Have you checked screws in frame holding main bearings?
Did you replace feathering shaft when you replaced blade grips...
Main gear tight, shaft holder tight and snug against the frame where it doesn't
move up and down?
Since its intermittent it sounds like it's an issue of something
getting out of whack around the rotor head or in the drive train
Or maybe something is slipping in and out of place..
That's the only thing I can think of...

[JonJet]

My guess is that you've got a vibration messing with the gyro unit...

I had an SR years ago and they were very touchy with respect to how/where the gyro was mounted - I ended up parting it out, but the DX6i that came with it served Me well until I got the DX9

Just MHO

[therick04pp]

New feathering shafts, shaft collar is snug no binding but no play up or down. All screws are tight.

I even tried remounting the gyro with fresh gyro tape, 3 layers. Should I wrap something around the gyro to snug it down more (seen people use zip ties/velcro straps)?

[nighttrain06]

Do you happen to have a spare gyro? I only use one thick piece of tape on mine, thats it.
What about the swash holder thingy in back? Binding? cracked? try to gently pull it apart....
I had one that secretly cracked on me....didn't really notice a difference in anything but ya never know....

[nbells]

I note you say ..... "and only a few feet from the ground"

First of all make sure you are well out of the ground effect before doing any diagnosis. With the SR you need to be at least above 5 feet to avoid issues.

Try running the bird with no head on, check for vibrations, there should be none. This then rules out the motor, main gear and main shaft.

Slowly rebuild the head, trying it each time to see what part introduces the vibration.

A couple of things to watch out for / try........

Ensure your dampeners are perfect and that you have the correct amount of shims either side. When turning the blade grips they should be smooth as well.

Ensure the mixer arms are orientated correctly and mounted the correct way .

Tightness of the main blades is correct. Turn heli on its side and they should just start to drop from the horizontal.

[nighttrain06]

Well Howdy Nigel! Glad the expert checked in I was treading water trying to help this guy!

[therick04pp]

Originally Posted by nbells

I note you say ..... "and only a few feet from the ground"

First of all make sure you are well out of the ground effect before doing any diagnosis. With the SR you need to be at least above 5 feet to avoid issues.

Try running the bird with no head on, check for vibrations, there should be none. This then rules out the motor, main gear and main shaft.

Slowly rebuild the head, trying it each time to see what part introduces the vibration.

A couple of things to watch out for / try........

Ensure your dampeners are perfect and that you have the correct amount of shims either side. When turning the blade grips they should be smooth as well.

Ensure the mixer arms are orientated correctly and mounted the correct way .

Tightness of the main blades is correct. Turn heli on its side and they should just start to drop from the horizontal.

It happens no matter what height I am at, I stay at or around 6 feet(ish) normally but need to go lower to land it fast when it happens. It's definitely a mechanical wobble and not ground effect. I should have noted that it doesn't do this in idle up. Totally slipped my mind. Seems to attack at lower headspeed.

I have ran with no head and it seems smooth but have not tried to add things one at a time. That will will be next. I do know that it vibrates with no blades and no flybar.

Last night I took the blades off and left the flybar in place and spooled it up. The blade grips looked like they were 1/4 out of whack from one another. I grabbed them and gave them a wiggle (did not feel any slop or play) and spooled it up again and now they look like they are tracking perfect?? WTH. They have been changed several times now and this shaft has only 1 test flight on it, no crashes or hard landings.

I am using the microheli grips. There were no instructions included so I had to trial fit things so that everything felt good. I am using the dampers that came with the cnc head and have my grips set up with 2 step washers. One facing the grip and the other facing the head. There is no up or down play when they are installed so i am not sure how they looked like they were an entire 1/4 out of whack like my feathering shaft was severely bent. Should I add a shim to the middle of the washers? I read on here that someone was using just the two step washers and theirs were good to go, thats why I went that route but obviously something is up with them.

[nighttrain06]

Man it seems you've got it all covered, I wonder if say a main bearing getting ready to go out or even getting jacked slight misalignment for some reason. Do you have a different gyro to try?
Maybe it has some weird issue with it?

[therick04pp]

Just got my order in with new:

main shaft
main gear
flybar
feathering shaft
tail rotor
Revolution blades

Going to redo the grips with a shim in between the step washers and install the new parts to make sure they are straight. Ill update after a test flight (currently getting pounded by mother nature in Mass so it could be awhile)

[FAST EDDY]

Originally Posted by therick04pp

New feathering shafts, shaft collar is snug no binding but no play up or down. All screws are tight.

I even tried remounting the gyro with fresh gyro tape, 3 layers. Should I wrap something around the gyro to snug it down more (seen people use zip ties/velcro straps)?

Now I realize that these things have been thrown at you.

Reasoning is what YOU are not looking at the most. We get ""WOBBLE"" in lower speeds due to "Balance" issues. The Higher the Head speed, the less the issue becomes. For the wobbles becomes "Less defined!~!"

So as it was said. Start by removing the WHOLE HEAD... Check each bearing and the Motor Mounts. It begins at the Bottom and work your way UP. The issue could have nothing to do with replacing the head. It is usually a compounding thing. Every little piece that Moves, ADDs Up in a Spinning movement of a weighted pieces!~!~!~!~!

Since YOU pulled your fly bar out and put it back in. Is it EXACTLY back in the center? The Micro Heli Cage is almost exactly ,87mm different than the plastic cage. Did YOU measure that and Split the Difference??? YES that is less than 1mm, and it caused a WOBBLE in Mine and it took Thinking out of the box and using up two sets of Bearings!~! for me to Break out the Calipers and really start Truly Measuring what and where MY Collars were!~!

Slow and Steady is the KEY and Knowing your Numbers are EQUAL!~!

Happy Thanks Giving and Holidays Every One

Mr Ed

[rudyrov]

Any way you can post some video?

[therick04pp]

Originally Posted by rudyrov

Any way you can post some video?

I was going to do this last night because I almost lobbed the thing against a wall.

Last night, I replaced the main shaft, main gear, feathering shaft and flybar rod. I installed the flybar rod with my calipers and is dead center. I did this last time as well but the rod was a little twisted.

I attached my new Revo blades, spooled it up slowly. 1 blade is about an inch higher than the other when tracking at about 15% throttle. I spooled it up more and it got worse so I shut it down. Took the blades off again and checked the grips. They are rock solid with no slop whatsoever. I checked the grip opening with my caliper they were way off. One grip is open wide and the other is closed up. Never noticed this before. They were brand spanking new and nothing but a single test flight on it, no crash.

So after all of this, it looks like I got some bum grips. Im not sure they can be "tweaked" so that both are perfectly parallel with the base of the grip and to one another, but if the tines on one are bent down slightly and the tines on the other are bent up slightly, this would translate into a BIG difference at the end of my blades. Thankfully I only paid $7.99 for this set. Off to ebay to find another set and hope these ones work.

Blade SR is a love, hate relationship.. ha!

[nighttrain06]

Originally Posted by therick04pp

I was going to do this last night because I almost lobbed the thing against a wall.

Last night, I replaced the main shaft, main gear, feathering shaft and flybar rod. I installed the flybar rod with my calipers and is dead center. I did this last time as well but the rod was a little twisted.

I attached my new Revo blades, spooled it up slowly. 1 blade is about an inch higher than the other when tracking at about 15% throttle. I spooled it up more and it got worse so I shut it down. Took the blades off again and checked the grips. They are rock solid with no slop whatsoever. I checked the grip opening with my caliper they were way off. One grip is open wide and the other is closed up. Never noticed this before. They were brand spanking new and nothing but a single test flight on it, no crash.

So after all of this, it looks like I got some bum grips. Im not sure they can be "tweaked" so that both are perfectly parallel with the base of the grip and to one another, but if the tines on one are bent down slightly and the tines on the other are bent up slightly, this would translate into a BIG difference at the end of my blades. Thankfully I only paid $7.99 for this set. Off to ebay to find another set and hope these ones work.

Blade SR is a love, hate relationship.. ha!

Well looks like one more odd thing that can take place and drive a man to drink......WOW!
I would have never thought to check that!
I'd at least try maybe putting it in a vise and gently seeing if you can maybe "tweak" em.
Give em a good look over to see if any stress cracks have occurred.
I'd try that first....do a couple of spool ups see how she reacts.

[therick04pp]

Originally Posted by nighttrain06

Well looks like one more odd thing that can take place and drive a man to drink......WOW!
I would have never thought to check that!
I'd at least try maybe putting it in a vise and gently seeing if you can maybe "tweak" em.
Give em a good look over to see if any stress cracks have occurred.
I'd try that first....do a couple of spool ups see how she reacts.

SERIOUSLY!! Bring on the beers..haha
No cracks or stress marks. they still look brand new. So weird. I used a set of pliers to gently squeeze closed the open ones and open the closed ones until my caliper gave me the same reading on both sides and both appeared to be open the same height from the bolt end to the blade end. My only issue now is how to check to make sure both tines are exactly center with the feathering shaft and not both slightly bent up or down.

Thinking I can slide a long screwdriver through both grips and check the distance of each tine to the screwdriver shaft. That should tell me if either grip is bent up or down slightly.

[nighttrain06]

Originally Posted by therick04pp

SERIOUSLY!! Bring on the beers..haha
No cracks or stress marks. they still look brand new. So weird. I used a set of pliers to gently squeeze closed the open ones and open the closed ones until my caliper gave me the same reading on both sides and both appeared to be open the same height from the bolt end to the blade end. My only issue now is how to check to make sure both tines are exactly center with the feathering shaft and not both slightly bent up or down.

Thinking I can slide a long screwdriver through both grips and check the distance of each tine to the screwdriver shaft. That should tell me if either grip is bent up or down slightly.

Oh yeah, that could be an issue too....I have this cheap little screwdriver that just fits those bearings....slides right through....it's been great for removing those bearings on the ends.
I'll have to remember to check the grips I got from that sale too! I've been flying the one SR with
stock grips forever, if I break em I'll switch em over to the new metal ones.....

[FAST EDDY]

So after all of this, it looks like I got some bum grips. Im not sure they can be "tweaked" so that both are perfectly parallel with the base of the grip and to one another, but if the tines on one are bent down slightly and the tines on the other are bent up slightly, this would translate into a BIG difference at the end of my blades.

Blade SR is a love, hate relationship.. ha![/QUOTE]

THERE it is THERE!~!

[nighttrain06]

Originally Posted by FAST EDDY

So after all of this, it looks like I got some bum grips. Im not sure they can be "tweaked" so that both are perfectly parallel with the base of the grip and to one another, but if the tines on one are bent down slightly and the tines on the other are bent up slightly, this would translate into a BIG difference at the end of my blades.

Blade SR is a love, hate relationship.. ha!

THERE it is THERE!~! [/QUOTE]

Ha ha, yup we've all been THERE!
I have to say though, here lately it's been more love for my SR's
They are both flying very nice! But I worry the slightest nick of the
blade, too hard a landing will send me into the insanity of head scratching,
wondering, thinking, brooding, searching forums, and burning the midnight
oil, trying to find the cause of another mystery illness
that has afflicted my little heli.....lol

[therick04pp]

Originally Posted by nighttrain06

THERE it is THERE!~!

Ha ha, yup we've all been THERE!
I have to say though, here lately it's been more love for my SR's
They are both flying very nice! But I worry the slightest nick of the
blade, too hard a landing will send me into the insanity of head scratching,
wondering, thinking, brooding, searching forums, and burning the midnight
oil, trying to find the cause of another mystery illness
that has afflicted my little heli.....lol[/QUOTE]

* as I am reading this, I am doing exactly that*.. haha!

[nbells]

Don't know if you got this sorted yet or not, but could you post a clear close up pic of the head once its built. Try and get from the main gear up to the flybar if possible.