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Old Jul 19, 2007, 10:55 AM
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Joined Jun 2007
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why is it impossible to get perfect blade tracking as well as even blade pitch??

Today I decided to try and do flips on my T Rex 450 SE. Went over Finless Bob's throttle and pitch curves video.

I set each individual blade for +11 max hi -- 0 mid stick -- and -11 max low. Went to the field and went crazy with the flips. Finally!!! I was so happy to finally get over my fear of trying to do flips cause the last time, I ended crashing (so nervous and didn't have enough altitude).

It wasn't when I decided to hover in front of me that I noticed about a 3mm or so gap between the blades. I went and tried to adjust tracking, but in doing so, I know that I messed up the pitch setup that I had previously done.

What is more important; good blade tracking or even pitch on the blades? Seems like I can't have both. Am I missing something here?

Oh yeah, the blades are 315mm carbon Align blades (could I have a bad set of blades?). Thanks
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Old Jul 19, 2007, 11:30 AM
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Mochaboy's Avatar
United States, MA, Sudbury
Joined Aug 2006
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Quote:
Originally Posted by newtukatukpilot
What is more important; good blade tracking or even pitch on the blades? Seems like I can't have both. Am I missing something here?

Oh yeah, the blades are 315mm carbon Align blades (could I have a bad set of blades?). Thanks
It's not impossible. Far from it, but like anything else, it takes time and experience to do it right.

If you recall from FB's blade tracking video, he tried balancing a set of Align Carbons that were so badly out of balance CG wise, that he was considering just sending them back.

Anyway, to your problem:
1) What method did you use to balance the blades?
2) what specific tool did you use to balance the blades?
3) did you balance them staticly, or dynamically?
4) did you balance the flybar as well? People often overlook the flybar which is capable of inducing an out of pitch condition.
5) how tight are your blade grips?

Once you get the blades balanced, at zero pitch, you shouldn't have to turn the low blade by more than 2 or 3 turns to get the tracking on point.
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Old Jul 19, 2007, 11:33 AM
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United States, CA, Chico
Joined Feb 2007
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Ok first you know you have dampers that need to be check regularly right?
Next hold your blade grips with one hand and turn the allen screw in one side clockwise. Is your feathering shaft bent? You will feel it if it is.

Ok now this.
Mark one blade grip as master. Get your pitch right on that blade. -11 0 +11 yada yada..
Ok now get the other blade to track the master blade.

Notes:
The short link from the lever to the blade grip will give you 2 degrees.
The long link on the pitch lever going to the swash plate will give you one.

If you are not level on your head it will mess with tracking.
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Old Jul 19, 2007, 11:37 AM
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Joined Jan 2006
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what you need to do is make one blade grip / blade a master and mark it.

Then you adj the other blade if tracking is off... this way you know that you wont mess with your ptich rang and such...

EDITED:

LOL HS beat me to it... started typing this and had to step away from the desk
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Old Jul 19, 2007, 11:37 AM
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Also... Don't be afraid to go a 1/2 turn on the ball link if needed! you can unscrew the ball from the swash or mixing arm, put on the link from the inside, then screw it back in.

not only can this help get that perfect tracking. the ball link is less likely to pop off completely...
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Old Jul 19, 2007, 11:39 AM
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also.... if your tracking is only out on 1 side of the rotor disk... that is something bent in the head.... usually a spindle..... true tracking problems are equal on both sides of the rotor disk while in the air.
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Old Jul 19, 2007, 11:46 AM
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Joined Jun 2007
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I balanced my blades using the the cheap Align blade balancer like the one FB used on his tracking vid. I did not balance the blade CG w/ a mainshaft as he did on the vid. Instead, I just did it the fast way where I would line up the blades on the balancer, put it between 2 glasses, and then added electric tape (heavier and doesn't need as much to add weight) to the lighter blade until it was balanced. Should I balance the blade CG?

I did not check flybar balance. I just made sure they were the same length on both sides w/ a vernier caliper. How would I balance the flybar? Do I just find the centerpoint and then add tape? Wouldn't that make sliding of the flybar weights impossible?

I leave my blade grips loose, so that I can tilt it over and the blade will fall over slightly. I did this to make sure that the blades can extend to it's normal position when spinning. Is that too loose, or is it more important to have both grips the same tightness or looseness?

When you say 2-3 turns, you do mean full turns and to the longer links and not the shorter link attached to the blade grips right? Thanks
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Old Jul 19, 2007, 01:18 PM
Joined Nov 2005
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If your blade tracking has changed in flight, one of three issues is to blame.

1: You bent your spindle.
2: Your dampers are shredded or worn. Get new ones or get higher quality ones. Stock rubber o-ring dampers will get torn up in 3D flight regularly.
3: Your plastic ball link ends are worn. Replaced the ones that control your blade grips.

You can throw out the imbalanced blades theory unless he crashed, because they tracked true at the beginning of the flight yeah? You can also throw it out unless he has moderate vibes in his heli.

My money is on problem #1 or #2.

-Kyle

Edit: Large blade pitch changes are done on the short linkage rods. Small blade pitch changes are done on the long linkage rods.
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Old Jul 19, 2007, 01:21 PM
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Differential throw will also do it.

As someone mentioned before me, I would check the spanwise CG and wieght first.
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Old Jul 19, 2007, 02:16 PM
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To balance the blades you should get the CG matched first. Then add the weight at the cg. Gyroscopic force will change the effective weight of the blade compared to the other, if the weight is added away from the cg point.
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Old Jul 19, 2007, 04:24 PM
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Joined Jun 2007
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Quote:
Originally Posted by arclite5
If your blade tracking has changed in flight, one of three issues is to blame.

1: You bent your spindle.
2: Your dampers are shredded or worn. Get new ones or get higher quality ones. Stock rubber o-ring dampers will get torn up in 3D flight regularly.
3: Your plastic ball link ends are worn. Replaced the ones that control your blade grips.

You can throw out the imbalanced blades theory unless he crashed, because they tracked true at the beginning of the flight yeah? You can also throw it out unless he has moderate vibes in his heli.

My money is on problem #1 or #2.

-Kyle

Edit: Large blade pitch changes are done on the short linkage rods. Small blade pitch changes are done on the long linkage rods.

My blades were tracking properly before but I think the pitch was already off then. I started messing w/ the links to set each individual blade for 3D (-11, 0, +11). I didn't check tracking at the beginning of the flight; only at the end after doing flips. I'm guessing that they were already off track at the beginning.

I'm going to rebalance the blades and do it right. I thought I'd get lucky by doing it the easy way

My dampers only have about 10 flights on them, but I do have some more stock ones so I'll change them.

I hope I don't have anything bent on the head. I do have a brand new Dragonus rotor head set that's been sitting for about a month now; maybe I'll try it out. Hope it works out.
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