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HomeAircraftHelicopterAerial Photography and Video › Strange wobble...
03-04-2008 01:31 AM  10 years agoPost 1
djsegler

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Dallas, Texas - USA

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Anyone ever have a slight wobble that only affected the left skid? It seems odd that it would show up on one skid and not the other...

The heli is a Bergen Observer EB with a G26 running with a headspeed of 1550 where the wobble seems to be minimized...

Practice = Precision... No shortcuts...

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03-04-2008 01:45 AM  10 years agoPost 2
xcellgasman101

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WOODWARD, OKLA....

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First thing I would check would be the dampners in the head,, make sure they are not stuck, or dry,, Something to think about.. XGM/VGM

John Crotts
www.soonerhelicamproductions.com

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03-04-2008 03:06 AM  10 years agoPost 3
djsegler

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Dallas, Texas - USA

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Well, I took the head apart to fix some slop that I found on one side. Ended up replacing the spindle just for grins and all the slop went away. The dampeners are relatively new and Chris Bergen specifically requested that I not add any lubrication to them during installation.

This was prior to my present condition of having the wobble on one side only. Before doing this, the wobble was much worse and all over...

Practice = Precision... No shortcuts...

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03-04-2008 03:53 AM  10 years agoPost 4
xcellgasman101

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WOODWARD, OKLA....

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Well if Chris said, don't,,, then I would do what he told me, He must have a reason,,, I have always lube mine, when I start to get a wobble on the skids, and it goes away,, Xcell and Bergen's are pretty close in the head department???, I think.. One thing I do is pull one blade, and put a hex wrench on the spindle bolt, and try to turn it, if it is hard to turn,,, Then I will lube, if it turns free and smooth, then its good to go.. Just how I do it,,

Did Chris say why?? not to lube?? XGM/VGM

John Crotts
www.soonerhelicamproductions.com

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03-04-2008 03:57 AM  10 years agoPost 5
djsegler

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Dallas, Texas - USA

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I'll ask him.

Practice = Precision... No shortcuts...

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03-04-2008 04:05 AM  10 years agoPost 6
xcellgasman101

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WOODWARD, OKLA....

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I use Tri-Flow,, just a small amount on my finger, then rub all o-rings, or dampners, just a light coat is all I do.. Please let me know what Chris says,, I might need to quit for some reason that I'm unaware of.. Thanks, XGM/VGM

John Crotts
www.soonerhelicamproductions.com

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03-04-2008 09:44 AM  10 years agoPost 7
helisin

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Calgary, Canada

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Not sure if your wobble issue is the same. Not sure what you mean by left skid only. I just had a wobble issue...

Mine occured when spooling up. I had head speed at 1550 before blades even hit 0 deg. Wobble would start at aprox 0 deg pitch. As soon as blades loaded up above 1 deg pos pitch, wobble would dissipate while lifting off and it would fly smooth with nil obvious vibes. Wobble was negligable when coming into land and going from posiive pitch into and through 0 deg. Blade bolts were snug and nil obvious play or bent parts. I'm sure minor play in some parts will contribute to this.

Was given advice and adjusted rpm to be 1400-1450 through 0 deg and bring rpm up as soon as blades load up. That seemed to do the trick. Nice'n smooth through all blade angles now. Running 1550 head speed in flight - Intrepid EB. I'm still trying to replace anything with any play in it to keep flight controls predictable and vibes at minimum.

Rob.

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03-04-2008 12:42 PM  10 years agoPost 8
djsegler

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Dallas, Texas - USA

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Yeah - I definitely have to keep the headspeed lower overall and ease into it as well... There are the typical couple of resonances that you hit as you spool up, but this one is independent of those and only noticeable in the air.

Practice = Precision... No shortcuts...

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03-04-2008 02:53 PM  10 years agoPost 9
aambrose

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Pana, IL

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Another thing you might check is the tightness of your blade grips. If ours are too tight, we'll get some wobble.


Tony

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03-04-2008 03:00 PM  10 years agoPost 10
hgflyboy

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SoCal

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My T-Rex 450 had the same problem with an Askman mount attached. Turned out the main bearings were going bad . . .

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03-19-2008 09:49 PM  10 years agoPost 11
djsegler

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Dallas, Texas - USA

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Update -

While aligning the paddles and making sure that everything in the head was perfect did help with my wobbles and vibes, I discovered this weekend at B'Ham that my problems all went back to a bad plug.

The plug must have had a weak spark and unburned fuel was building up causing the engine to sag and produce the wierd wobbles I was having.

Moral to this story - always keep a fresh plug on hand. Might be a good idea to check the gap too to make sure the spark is appropriate for your motor.

I have had one recommendation from someone that Champion plugs have plagued him in the motorcycle industry for years and he strongly recommends NGK. I don't have any personal info with that to boldly state that myself, but FYI...

Thanks to everyone for the help, but it looks like I'm good now!!

Practice = Precision... No shortcuts...

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