Annoying Wobbles

[Avi_Y]

Hi,
Got my Whiplash rebuilt after an unsuccessful auto (one should land after his timer starts beeping...), and installed new maingear, mainshaft, feathering shaft, grip radial bearings, some plastic ball links, boom with torque tube, and one boom support. I also put on a fresh pair of SAB 710 (before I was flying Radix 710 and Maverikk WC 710).

Getting back to the field, I tried flying with the same setup as before, with headspeed of 1700 rpm, which is what I use in "normal" flight mode. However, I got bad wobbles. To make a long story short, I could not get rid of it without going to 1800 RPM or above.
I tried lowering cyclic gyro gains (Skookum SK720), and in fact went thtough the whole gain range.
I put on a set of Align 690, but this was even worse, requiring 1900 RPM to avoid the wobbles.
Head assembly is free of slopes, grips run smoothly, and there is no latheral play in the feathering shaft. All feathering shaft components are installed correctly, dampers are the clear soft, rounded side facing inward, and have no visible deformation (could they be damaged without it being visible?).

Any ideas for what to look at?
Thanks.

[paverpilot]

At 1700 head speed something as simple as having one blade tighter than the other one could cause the wobbles, How hard did it go in, was it on the head, Did you double check to make sure nothing is bent like the head block or a grip, I have had this problem many times after a crash but never with the whiplash, it is almost always a damaged bearing or something bent that i have missed, If it was me I would take the blades off and have a friend hold it while you spool it up and try to find the vibration that is causing the wobble, Hope this helps

[frito169]

Do you see any vibration in the tailfin that is the most noticeable place to see any. Considering it was in a crash it could be anything With a bearing or a shaft.

[Brian James]

Originally Posted by Avi_Y

Hi,
Got my Whiplash rebuilt after an unsuccessful auto (one should land after his timer starts beeping...), and installed new maingear, mainshaft, feathering shaft, grip radial bearings, some plastic ball links, boom with torque tube, and one boom support. I also put on a fresh pair of SAB 710 (before I was flying Radix 710 and Maverikk WC 710).

Getting back to the field, I tried flying with the same setup as before, with headspeed of 1700 rpm, which is what I use in "normal" flight mode. However, I got bad wobbles. To make a long story short, I could not get rid of it without going to 1800 RPM or above.
I tried lowering cyclic gyro gains (Skookum SK720), and in fact went thtough the whole gain range.
I put on a set of Align 690, but this was even worse, requiring 1900 RPM to avoid the wobbles.
Head assembly is free of slopes, grips run smoothly, and there is no latheral play in the feathering shaft. All feathering shaft components are installed correctly, dampers are the clear soft, rounded side facing inward, and have no visible deformation (could they be damaged without it being visible?).

Any ideas for what to look at?
Thanks.

The Whiplash was really designed with higher headspeeds in mind. The kit includes a set of blue, and a set of white (clearish) dampers. If you're wanting to run the lower headspeeds, use the white dampers, and make sure to lube them with some non-petrolium grease. We use Tri-Flow, or our Synthetic Hydrogen grease.

[Avi_Y]

Thanks for your comments.
I did not see any vibration in the fin, yet the SK720 logged more vibrations than usual, in a pattern that might be caused from a damaged bearing in the motor frequency. I'll check it out, but I must admit I did not thing a bearing related vibration may cause wobbles. I'll try to isolate it (doable with the SK).
Brian, I realize no one opts or the low speeds anymore, but I loved my 1005 gasser landing approaches so much, that I can't give it up easily, especially since the heli worked fine in this speed. I do use tri flow grease. I'll give it another try after sorting the vibe issue, and if it won't work I'll give up.
Thanks.

[Brian James]

Originally Posted by Avi_Y

Thanks for your comments. I did not see any vibration in the fin, yet the SK720 logged more vibrations than usual, in a pattern that might be caused from a damaged bearing in the motor frequency. I'll check it out, buy I must admit I did not thing a bearing related vibration may cause wobbles. I'll try to isolate it (doable with the SK).
Brian, I realize no one opts or the low speeds anymore, but I loved my 1006 gasser la ding approaches so much, that I can't give it up easily, especially since the Heli worked fine in this speed. I do use tri flow grease. I'll give it another try after sorting the vibe issue, and if it won't work I'll give up.
Thanks.

So, have you tried the white/clear dampers yet? They may be a little too firm for that headspeed as well. THey also do soften up a bit with time as well.

[Avi_Y]

Yes, as I stated in my original post, I am using the softer white/clear dampers.

[hndaluvr]

Take a good look at your head block. I found that the head block is susceptible to damage in a crash (especially if you hit the head hard enough to bend a feathering shaft). Bent mine ever-so-slightly in a failed auto also.
Spin the head w/o the head button installed... and observe the hole in the top.
Is it "true"?... if not, then this may be your problem.
Not something that you'd typically think would get damaged, but the nice cutout that they've put in it does weaken this part. happened to me and others.
Just give it a look.

[kumar2494]

check your boom supports. a loose one will cause a wobble even if you change your gain

[Avi_Y]

Originally Posted by hndaluvr

Take a good look at your head block...

In fact, it's a new head block. I damaged the original one during the build, and since the heli was noce and shiny, I had to buy a new one... I did not install it until the crash, when I had to replace the fethearing shaft. I will, however, try putting the original one on.

[Brian James]

Unfortunately, I think you may just be trying to fly the model with a headspeed that is lower than what it was designed for. As the headspeed goes lower, generally a softer damper is required. At this time, the white dampers are the softest ones available.

[Avi_Y]

I well understand that.
What would you consider lowest speed for it?

[RobertAbles]

Have you tried running your blades on the loose side in the main grips?

[RobertAbles]

...

[Brian James]

Originally Posted by Avi_Y

I well understand that.
What would you consider lowest speed for it?

Well, it'll depend a little on the temperature of the dampers, in a really warm climate you may get away with lower headspeeds, than a colder one. Since you mentioned you couldn't get the wobble in yours to go away until over 1800, I'd say that in your case, you found the low headspeed limit for your model, at the temperature you were flying at. As the dampers wear in a bit, you may find that you can go a little lower.

[Avi_Y]

ok, thanks.
I'll try to keep everything in shape, and wait for some softer dampers to be produced... :-)