violent head wobble on spool down

[ahunter852]

Hi Guys,

Just built up a brand new warp 360. Everything seems smooth, but i have some pretty bad ground wobbles on spool up and spool down. the spool down is the worst, it almost tips the heli over the wobbles are so bad.

Im not really sure whats causing it. The blade grips seem to have equal amounts of play and are very smooth. Bearings seem seated well. blades are edge 353's. with out the blades everything is silky smooth. once i put the blades on i get quite bad vibes on the landing gear and these massie wobbles on the spool up and spool down.

blades are not on to tight either. My only thought is it could be the T hub, one of the holes doesnt seem to be exactly centred.

any ideas??

regards
Alex

[Shogun71]

I have my blades fairly tight with no issues.

I had similar with my atom 5.5. Tightening the blades up a little solved it.

Also what surface is this on? Hard, soft, grass, snow?

[Jeff_Barrett]

I sometimes get a bit of ground resonance on spool up and spool down at a certain headspeed / blade pitch.

Try hitting TH mid air and mini-auto / float down, if you don't see it happen there, then try tightening your blade grips.

[fjoe]

Have you checked the main blade balance?

[Jeff_Barrett]

Originally Posted by fjoe

Have you checked the main blade balance?

Good point, I assumed everything was dynamically balanced.

[ahunter852]

Hi guys thanks for the info. Seems like tightening it helped a bit. However there does seem to still be bit of a head wobble in flight.

I will try dynamically balancing the blades? Do you guys balance with the head on the main shaft? I've heard some people doing that with the warp.

Thanks
Alex

[Jeff_Barrett]

To dynamically balance the head, you'll need something like a dubro prop balancer or make your own rig. I doubt the head needs to be balanced ... what RPM are you running on the head?

[ahunter852]

ive balanced the blades both static and dynamcially.
Still having some vibes. I think it might be the main gear. it seems to be fairly warped. no matter how many times I loosen and re tighten the white rings sitting on top and botth of the main gear, i will still get rubbing at certain points against the frame, and the motor and tail belt don't seem to track straight on the main gear.

anyone else have issues like this?

regards
Alex

[Jeff_Barrett]

I would double check to ensure the main gear section is assembled correctly.

I've rushed sometimes building or rebuilding and forgotten the spacer or assembled it incorrectly.

My main gear has a tiny bit of warp to it as well, but it runs smooth as does the belt alignments.

Do you have some photos you can share?

[ahunter852]

Sorted out the blades and the main gear! Just did as you said and went over that part of the build again. Turns out one side the One way unit wasn't seated properly on the main gear. Gear looks fine now. Visible vibes gone.

However Vbar is still telling me I have raised vibe levels and the wagging drifting tail seems to co orberate that.

Any ideas?

[Jeff_Barrett]

Excellent to hear you've got part of the issue licked!

Are you able to post the vibe analysis log as a JPG so we can see where it's coming from?

[ahunter852]

Thanks for your continued help Jeff, really appreciate it.

I took her up for just a quick hover and I'm still having a wag/drift.

The extreme vibes I beleive came from spool down (had the blades on a little to right I think).

[Jeff_Barrett]

It's no problem at all. I'm here to help.

Do you have the actual analysis graph that shows the frequency at which the vibration is coming from?

[ahunter852]

I have had a look through the vbar program. I don't think the mini vbar has that function.

[Fooferdoggie]

Tracking or a misplaced washer in the head can cause this 1.2 turn on my gaui link kept the start and stop vibes from happening.

[Jeff_Barrett]

Does the tail control rod appear to be vibrating?

Mine gives a bit of wobble at a certain RPM on spool up and spool down ... possibly ground resonance.

[ahunter852]

Just had a little test hover. No visible vibes on the tail rod or fin.

[Ah Clem]

Drift is usually caused by high-speed vibration (motor, tail rotor, etc.) feeding into the FBL unit.

Tail wag is usually caused by too long of a rudder servo arm (the length stated in the manual is incorrect, by the way), binding in the linkage (links themselves tight on the balls, tail collective spider links not moving freely on the hinge pin, etc.), tail bell crank ball binding.

Does the tail pitch change mechanism move completely freely?

Have you lubricated the tail shaft where the slider moves over it?

[ahunter852]

The tail seems to move quite freely. I have lubed the tail shaft.

What hole should i use on the servo arm for the tail? How many mm out from centre?

[Ah Clem]

5-8mm.

You will get a variety of answers on this, but I think most are in this range.

I installed the 19T tail pulley to see what it did. It allowed me to increase the tail gain before the onset of wag, resulting in better overall tail hold.

This is not necessary, as I flew it a lot with the stock tail pulley first and it flew well.

The drift may be very easy, or very hard to get rid of. Every FBL unit that I install now, regardless of brand, gets installed with 3M 411 tape. The stock V-Bar tape seems to work pretty well, with the V-Bar. Some of the stock tapes seem to almost amplify high frequency vibration. I know that the tape that comes with the BeastX works better if you remove the rectangular section that is die cut in the middle of it (at least, this was the case for me).

Wires flapping or tapping against the FBL unit, or trapped under it, can cause some very interesting and very undesirable behavior.