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Interesting Blade Tracking Problem - Suggestions or Help Appreciated

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Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Old 06-29-2008, 01:42 PM
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Yarm6
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Default Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Hi Everyone-

I have an interesting blade tracking issue (well, at least I think it’s interesting) that you all may be able to help me out with. When I do my blade tracking, it’s usually at about 70-80% throttle (i.e. in hover) and I can get the blades to track. I noticed that after tracking is done, and I move the cyclic, the other blade seems to “snap” out of tracking and rides higher. For example, when I first start to do the tracking, the red blade, say, rides high. Then they both track and they are fine. As I move the cyclic around, the blue blade will snap out and always ride higher, even if I move the links down. It stays higher, and it really seems to “snap”. Sometimes the red one will snap back for a little as well.

Here is the equipment I’m using
HBK2
Stock Esky Woodies
3900 motor
10 tooth pinion with Blade 400 gear (also this happened when I was using the 9T and stock main gear)
Xtreme Turnbuckles and 43T pulley
Metal swash and washout

When I searched the forums, it sounds like the wood blades aren’t great. I have balanced and adjusted the cg best as possible on the blades. This happened on my last set.

Can head parts wear out to cause this? I’ve checked the usual and replaced the feathering, main and flybar shafts and all that other good stuff. I’ve even made sure the flybar center holder is not broken (i.e. the little tabs that ride in the bearing and cause all kinds of tracking problems),

Should I just ignore this with the woodies? Would this go away with carbons? Is there anything else I should replace such as the blade grips? I’m wondering if I should just replace the flybar center holder and other pieces (control arms) anyway to see. Any help would be greatly appreciated. Sorry for the long post, you guys have been so helpful! I love flying this little thing around.

Thanks,
Dave
Old 06-29-2008, 06:33 PM
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DumbDawg
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated



Are you still with plastic or you have cnc head??? Plastic is a little harder to keep tracked because of the slop in the plastic.

I haven't had that much trouble with the woodies. I balance mine out the best I can and forget about them... they are cheapies so you can't exactly expect them to track flawlessly.

It also depends on the type of flying you are doing. If all you are doing is hovering or some FFF then the woodies are fine. Anything moe extreme the CF is probably what you might want to get.

hope this helps... happy fly'n
Old 06-29-2008, 09:13 PM
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Yarm6
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Thanks for the info Dawg. Oh, I’m using the plastic central hub, blade grips and flybar seesaw. The swash and washout are Microheli. This is still the same blade grips and central hub (replace the flybar center holder multiple times along with the feathering shafts). I wonder if they are getting worn. The head does seem to have more slop than usual. I can actually hold the grips steady, and move the flybar up and down slightly.

I just can’t figure out what part of the grips or others actually wears. Is it the plastic balls, or maybe in the grips where the bearings go, causing it to move differently. Would replacing the linkages help as well? Not a big deal, just looks a little weird in the air with a gap between the blade tips.

I’m doing mostly hovering and circuits in the back yard, so no 3D yet. Wasn’t going to use carbons for awhile. Just was wondering if there was something wrong with my setup. I like the woodies (mostly because they explode on a hard crash), maybe just a tired pair that I have.
Thanks for your help.
Dave
Old 06-29-2008, 11:52 PM
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kenhiraihnl
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

since you can hold the grips, and still move the flybar up and down, that would indicate a source of excessive slop, and maybe something broken...make sure none of the tiny beveled screws are not stripped in the plastic head...there's a hundred ways to assemble spindles - with spacers, step-washers, flap bushings (o-rings), etc...try to pull the grips apart, and try to move them up and down (flap)...they should be snug, but feather easily...also, the m2.5x16 blade retention bolts don't last forever...ken
Old 06-30-2008, 12:45 AM
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

You set the pitch and when you check the tracking it is way off even when the pitch is correct? Is that right?
It appears to be only one blade and when you get the tracking dialed in you find your pitch is off by several degrees on one blade?
This can be caused by two things in the upper part of the head one is the weakest link in the head which there are one of for each blade. On the top of the head on each blade there is a seesaw that has the long link that you adjust blade tracking with on one end and short link that attaches to the blade holder. The screw that holds this little seesaw to the head has a habit of comming loose and wobbleing a little (just a little will translate to a lot of sudden slop) Be sure it is tight (not stripped either) and also not worn out or the bearing worn out. If you look at behind it there are two tiny phillips screws that hold the flybar in place, make sure these are tight and not worn or striped.
The CNC washout due to the way the seesaw arms on it are attached they tend to work lose then strip and wobble. Since it is metal you need to clean out the thread holes and the inside bore of the bearing and replace the bolt, on my washout this done with a longer bolt, 2x10 mm old one was 2x8 locktite it in let it dry. the little brass cone washer has the poiny cone side towards the bearing in the arm, also dont get Loctite on it or the arm or bearing. Put the screw through everything apply the Loctite to the screw or into the threads with a toothpick and install. Loctite only works on clean surfaces that dont have any oil or old Loctite on them.
Also check that your washout is not installed upside down!
If the long links that you adjust the tracking with appear to be very close or touching the mounting bolt for the seesaw then it upside down. I found out by measuring a new cnc washout the play (slop) with a dial indicator that the stock plastic washout has about 50% less play or slop in it. Some is due to the tighter fit of the pins on the side but most was due to the way the seesaw arms were mounted. Where as the plastic flexed a tiny bit the cnc had loose play in the linkage itself which amounted to more play then the plastic had flex. I went back to a plastic washout and my hover was immediatly improved.
Old 06-30-2008, 05:53 AM
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jh1947
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Forgive me, but anytime I come across a post concerning tracking troubles, I feel compelled to submit this link
[link=http://www.youtube.com/watch?v=HwJA8McHNsg]Fly bar Video[/link]
Am going to assume that you've already determined that the feathering shaft is not an issue (its absolutely straight).
One other area that's often overlooked is the arrangement of the thrust washers in the blade grips. The washer W/ the smaller hole needs to be on the nut side of the bearing.
The difference in hole size is small. I find the easiest way to determine which has the smaller hole is to place both of washers on a feathering shaft & look for the one that has the least amount of slop.
If you haven't been conscious of this difference in the past & have had the both thrust bearings torn down. It may be worth while to compare all four washers, and pair them back up.
Old 06-30-2008, 01:07 PM
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funflier
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Good point JH I have installed them backwards a few times and noticed a little more headplay then before.
Old 06-30-2008, 05:36 PM
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Zimatosa
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

I also posted a fix for slop in the center fly-bar holder using an align feathering shaft. Make sure to read my comment in the text area under the playing video first. If you have a few basic mechanical skills, this mod is no problem! This was one of the greatest things I did to the plastic parts to eliminate slop...You can get it as tight as you need it to go and it will not strip out ever again. [link=http://www.youtube.com/watch?v=aJmoido-SqY]Fly-bar mod vid[/link]

Another killer fix is to buy the CNC center fly-bar holder from Micro-heli or cnchelicopter. It is a great little replacement if you don't want to upgrade to full CNC at this point....

peace,

Z
Old 06-30-2008, 09:15 PM
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Yarm6
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Hi Guys-
Thanks for all of the help and suggestions. I worked on my heli today and think I have it pretty much fixed. It boiled down to two problems (one was more major than the other). First, I think I had my washout plastic “A” arms and Ti turnbuckles on the wrong balls on the swash. I had the tracking adjustment linkages on the balls that stick out further and the washout arms on the balls closer to the swash. This should be reversed. I just never noticed this until today!

Second, was what Ken and funflier were talking about. I broke down my head and as I was doing it, I noticed that the two black flathead screws were not fully inserted into the flybar center holder and were not tight at all. I tried to seat the bearings so they would support the small frail shaft on the flybar center, but as they got closer, I couldn’t tighten up the screw without binding. Once I moved the bearings back slightly and tightened up the screws, tracking instantly improved! Thanks for your help and suggestions. I can’t believe what a difference the tightness of these screws on the flybar center holder makes on tracking.

I did check my thrust bearing order. I have a neat screwdriver that fits perfectly. It lets the larger ID washer fall down, and keeps the smaller ID washers up higher, so that’s the way I tell. Good trick about the free play on a feathering shaft.

Jh – great video, I found that out the hard way on several crashes that on old center holder parts, I had a fractured pivot and didn’t know it, but my tracking was horrible. Replaced the part and it improved dramatically.

Zim – Wow, what a great mod. I bet you never have to replace those stupid flybar center holders. I’ve gone through a bunch already. I am a mechanical engineer and can get Align feathering shafts, so I’ll have to try it. If I screw it up, it just is one flybar center holder. No big deal. I love tinkering with these things.


Thanks everyone again for your help!

Happy flying!

Dave
Old 07-01-2008, 08:15 AM
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dicharry
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Default RE: Interesting Blade Tracking Problem - Suggestions or Help Appreciated

Zimatosa, I noticed the CNC flybar holder dosen't seem to include the tiny screws that screw into the holder from both sides. Is the CNC holder threaded to accept the OEM screws ?
Thanks,
Don

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