7hv ultimate main rotor woble

[KatoSan]

Hello guys.

I came back to Compass family 3 months ago buying a second hand 7hv ul.
Indeed I was already dreaming about It in 2010 when It was a prototype.
My 7hv was in good condition exept a delrin fbl tube that was damaged.

I decided to change the fbl arm by the chronos one and i have a main rotor head woble at some rpm range.
When my 7hv is between 1720 and 1930 rpm my Heli is shecking under the main rotor.
I Fly It with a Brain gyro, rjx servos with 3D défaut setup. I use 70 of agility.
I tried several lower value of cyclic gain but Nothing have changed.

Any idea ? Does someone experiencing the same issue ?

Ps :
-my dampers are new
-I tried SAB, i Fly rail : no change
-I tried 2 Brain on my 7hv
-I don't Fly latest Brain firmware.


Thanks for help

[cyclo]

Are the blade grip dampers still tight? If not maybe its time to replace them. If you do so, apply silicone grease liberally to the dampers before you insert them to the blade grips.

EDIT: Just saw that your dampers are still new... In any case I would apply silicone grease to them before putting them in the blade grips.

[quinn]

If you generally fly lower headspeeds, try the blue dampers

[KatoSan]

Hello guys

Thanks for posting.

@ Cyclo, I put silicone grease in the inner hole of the damper to insert the shaft. No grease in the outside between the Blade grip and the damper. Should I ?

@ quinn, i Fly 2 Speeds, half the time with a pack. 1700 and 1950 rpm.
At 1700, wobles appear sometimes when i'm on statio. When I Fly and doing 3D I'm not sure i have them.
If i lower the speed to 1600-1650 i don't have the wobles but i'm not fan. Minimum for me is 1700.

At 1950 it's ok but of i put 1900 that is the high speed i wanted, It wobles every time.

Strange.

[KatoSan]

Perhaps i have a clue that chronos or 6hv owner can also help.
My fbl arm that i put instead of the stock ones are suspect for me.
I explain : i build them respecting the orientation with the rond curve towards when rotating. I noticed that the external face was not the same, see the pics :



The front one have a rectangle mark face to outside. The back one have this mark in the inside.

IS that normal ? Are there other 7hv owner that put this arm in their bird with succes ?

[Djhandz]

This is quite a comman issue for some with the 7hv see the wobbles over 1600rpm thread.. for me the only fix is to loosen the boom support clamp this takes care of it for me. I tried everything else with no success. Hope this helps

[scoio]

Originally Posted by Djhandz

This is quite a comman issue for some with the 7hv see the wobbles over 1600rpm thread.. for me the only fix is to loosen the boom support clamp this takes care of it for me. I tried everything else with no success. Hope this helps

Mine holded till 1400.. less then that wobbles appeared, using the lime green dampers tho.

[vinnyd]

Originally Posted by KatoSan

Perhaps i have a clue that chronos or 6hv owner can also help.
My fbl arm that i put instead of the stock ones are suspect for me.
I explain : i build them respecting the orientation with the rond curve towards when rotating. I noticed that the external face was not the same, see the pics :



The front one have a rectangle mark face to outside. The back one have this mark in the inside.

IS that normal ? Are there other 7hv owner that put this arm in their bird with succes ?

You have your arms on the correct way. Fat edge leading like a blade. My markings are the same as yours. One oriented inward and the other oriented outward. I am running these arms on both my 6hvu and 7hvu. Running 2050 headspeed on the 7hvu.

[vinnyd]

Originally Posted by KatoSan

Hello guys

Thanks for posting.

@ Cyclo, I put silicone grease in the inner hole of the damper to insert the shaft. No grease in the outside between the Blade grip and the damper. Should I ?

@ quinn, i Fly 2 Speeds, half the time with a pack. 1700 and 1950 rpm.
At 1700, wobles appear sometimes when i'm on statio. When I Fly and doing 3D I'm not sure i have them.
If i lower the speed to 1600-1650 i don't have the wobles but i'm not fan. Minimum for me is 1700.

At 1950 it's ok but of i put 1900 that is the high speed i wanted, It wobles every time.

Strange.

Yep apply a liberal amount of grease on both the inside and outside of the dampers.

[quinn]

Originally Posted by vinnyd

You have your arms on the correct way. Fat edge leading like a blade. My markings are the same as yours. One oriented inward and the other oriented outward. I am running these arms on both my 6hvu and 7hvu. Running 2050 headspeed on the 7hvu.

Same here, have them on both, working great. Sometimes I go down to 1800 and it flies well. Also I fly 6s for about 1200 or so.

[Smoggie]

The softer blue dampers along with slightly reducing cyclic gain fixed it for me.

What also seemed to help was converting to the conventional radius arm swash driver head. In fact you might well find that the more flexible standard 7HV links work better for low HS rather than the moulded ones off the 6HV.. The stock ones are much more flexible which should allow the head to articulate more, especially when using the softer dampers.

[Ah Clem]

Also, you might try turning the gain down on the cyclic in the FBL unit. The three ways to get rid of a high frequency shudder are:

1) Increase RPM
2) Softer Dampers (KBDD Royal Blue, as suggested above).
3) Lower Cyclic Gain

Also, look at the "SZ" arms-with one snapped onto its swashplate ball, does the other one align perfectly with the ball on the other side? If not, you can add one or two of the very thin washers between the "SZ" arm bearing and the blade grip arm on one side to get them to match exactly. This has been known to reduce shuddering.

If is it a vibration and all is balanced, make sure the dampers are lubricated with silicon grease (also mentioned above).

[acidla]

I also had good results from the blue dampers @ 1910rpm.

[cyclo]

Originally Posted by vinnyd

Yep apply a liberal amount of grease on both the inside and outside of the dampers.

+1. This is what I do. I am using lime green dampers and mostly fly at high headspeeds.

[KatoSan]

Hello guys

Thanks a lot for your suggestion. I'm going to put grease inside and outside the dampers. I will also buy a delrin arm to test the 7hv stock fbl arm.

I really like the way this bird is flying except my woble.
I hope i will succed in solving it because i like 1700 and 1950 rpm.
I'm ready to sell my Trex 700 dfc pro and maxi. Perhaps a Chonos wil complete my 7hv.

I'll keep you posted.

[KatoSan]

I'm about to buy some grease, stock FBL delrin.
I notice that there was two models of damper
MTT-KB4112 MTT-09-0109
The second one is installed on my 7HV. What are you oftenly using ?

[renaudrenaud]

Hello Katosan
I use the Damper MTT-KB4112 with great succes on my 7 HV.