EVO 50 head balance

[MO_Helinut]

I would like to know how would be the best way to balance a rotor head, I balance the blades but when I spool up it shakes alittle hard until it reaches about 1600 rpm, I fly around and it seems fine, but when I land and spool down there is a point that it starts to shake again, I'm wondering if my head is out of balance. any help would be appreciated!

Jorge

[SteveL]

Have you had a crash? I have seen this when the AL hub gets bent. How tight are you blade grips? Blades should not move freely. If they do is will cause a lead lag on spoolup and slow down.

[MO_Helinut]

No, It's new, only have 4 flights on it.

[mudbogger2]

When you are first spooling up the blades are out of position in the blade grip. This causes an out of balance condition untill the centrifugal force causes the blades to center in the grip.

Another issue is with the Evo 50 it will shake at low headspeeds usually 1550-1600 or below will cause a nasty shake. It just does not like low headspeeds. Keep the headspeed over 1600.

[MO_Helinut]

I understand that, but after flying the when you land and watch it spood down it has a shake, you let the blades stop then spool up again and before it reaches 1200 rpm it starts again but goes away when you reach higher rpms, anyhow I'm going to try balancing the flybar paddles and see where it takes me.

[mudbogger2]

are you flying off grass or a hard surface like concrete?

[MO_Helinut]

Flying off grass. here is what I did also, I removed the blades and the main gear, set the heli on it's side and noticed that one paddles seem to drop like it was heavy, when I use my calipers that paddle was almost 2mm farther out than the other side, so I moved it in to match the other side then they would set even, maybe that was the problem. wish the weather would let me test it, I guess I will find out in the next few days.

[vera]

If you take all the links off the flybar - and get them out of the way - the flybar should teeter freely and balance.

Fire it up without the blades - being careful not to rev it up beyond normal - to check for a non-blade related vibration.

[MO_Helinut]

Vera,
That's close to what I did except spooling it up without blades, soon as the weather gives I'll test her out.
:glasses2:

[Ivan]

This is what was called the "Raptor Shuffle" back in the days of the RV1. Dampening affects this, do you have the infinavation or the carbon extreme dampers installed, harder dampers help.

Also, are you using blades that are perfectly balanced or just using the bolt them together and see which one hangs trick? If they are wood blades and the cord wise balance is off, they can have lead lag differences that will cause shake at certain rpms.

The reason it goes away at higher rpms is harmonics.

My sceadu will wobble terribly if I let teh head speed get too low in autos, so it might also be inherent.

[MO_Helinut]

Ivan,
I have the stock dampers that came with the kit and the blades I'm using are MAH carbon, and they have been balanced perfectly, If you read above I have made changes and will try it out tomorrow when I go out and fly; but i am thinking of installing harder dampers anyway. It's a new bird and I want to work out any bug before I start upgrading.

Thanks,
Jorge

[Ivan]

I have the infinavation ones in my skiddy now, and I think I like them a tad better than the micro ridge ones that I had before. Just my opinion.

It has also been my experience that the paddles will not generally lend to a visible shake. They are usually pretty light and much closer to the center of rotation than the center of mass of the blades.

I know you said you have a set of respectable carbon blades, but have you actually checked them on a Koll or like balancer. I have had some quality blades come up out of balance.

One other thing I thought of is to make sure the main rotor hub can not wobble on the main shaft. On the Sceadu, the shaft doesn't stick into the hub very far, so make sure the top Jesus bolt is tight.

[MO_Helinut]

the problem is solved! those corrections I made did it! put some flights in today and she was smooth and I was able to open her up, I was surprised on how well it handled and the power this bird has. very happy puppy here! :thumbup:

[MO_Helinut]

Oh!

I want to thank everyone that gave me thier input. :cheers