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HomeAircraftHelicopterHelicopter Main Discussion › Static tracking on Predator...
02-21-2013 03:41 PM  5 years agoPost 1
flyinfriend

rrApprentice

North American continent

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I measured static tracking on my Century Predator gasser and one blade is about 1 cm higher. The blades track perfectly fine in flight but I am trying to track down a vibration issue. It isn't a violent vibration but it is visible in the tail intermittently and it's a side to side vibe. Is the 1 cm blade height difference too much?

I had a hard auto over 1 year ago and replaced main, feathering, and tail shafts. I am going to see tonight if I have any room for adjustments as to how the head is clamped onto the main shaft. There may be room for slight adjustment to try and get rid of the 1 cm difference. The head is held on with a Jesus bolt and two pincher bolts on the sides.

Thanks for any thoughts on this.

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02-21-2013 03:51 PM  5 years agoPost 2
jschenck

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La Vista, NE.

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check the tail blade balance - my Predator tail blades were out of balance from the kit.

Also clutch alignment is a really big deal. It's a heavy clutch so if it's off center by .001" of an inch it can cause vibrations.

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02-21-2013 04:00 PM  5 years agoPost 3
helixangle

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Mamaroneck, NY - USA

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one thousandths of an inch...really, I have a micrometer that will read that, just don't know how to get a toy within those specs, any advise?

Be sure the juice is worth the sqweeze
Remember life is hard...even harder for stupid people

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02-21-2013 04:13 PM  5 years agoPost 4
flyinfriend

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North American continent

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Thanks, I should have been more clear, the vibe is seen as an occasional left/right vibe in the tail and not up and down, again it's not violent and not constant.

I am running the Century carbon tail blades. The closest I could ever get the clutch/fan assembly was just under .002". Part of that was due to the g231 drive shaft tolerances and if I remember correctly that was just under .002" as well. I tried all positions of the fan to offset and the best I could get was about .0018.

Could the 1 cm off in static tracking (blade height) cause this issue? Possible the head is cocked to one side a bit?

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02-21-2013 04:35 PM  5 years agoPost 5
JKos

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Redondo Beach, CA

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I don't think you're going to find many (any?) folks who measure the static tracking. That being said, 1 cm does seem like a bit although you are dealing with longer blades.

Here's a test for you... Swap the blades keeping track of which one is which (which one was higher, for example) and remeasure. Does the difference follow the blade or the side of the head?

- John

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02-21-2013 04:37 PM  5 years agoPost 6
flyinfriend

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North American continent

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Thanks John, I'll check that tonight.

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02-21-2013 04:49 PM  5 years agoPost 7
jschenck

rrProfessor

La Vista, NE.

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one thousandths of an inch...really, I have a micrometer that will read that, just don't know how to get a toy within those specs, any advise?

I use a little aluminum foil to move the clutch .001" one way or the other between the fan mount and the clutch.

with a Predator you can work it a little since it goes on a tapered shaft. lap in the fan mount on the shaft, oil it well and tighten down the fan hub slowly, measuring it as it goes on. I got mine on pretty straight. my crankshaft was not out of round though, engine was built by Hanson.

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02-21-2013 06:29 PM  5 years agoPost 8
Pistol Pete

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Seffner, FL

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I had a hard auto over 1 year ago and replaced main, feathering, and tail shafts.
Dampeners?

~~Enjoying the hobby one flight at a time~~

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02-21-2013 07:54 PM  5 years agoPost 9
helitom

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Pine Grove, Calif, USA

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+1 on the dampeners.

Also, the aluminum portion of the rotor head block can bend. If you wacked it hard enough to warrent replacement of all the shafts, you might want to check the head block.

The older I get, the fewer things seem worth waiting in line for.

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02-21-2013 07:55 PM  5 years agoPost 10
flyinfriend

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North American continent

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Thanks guys.

I was wondering about the head block, thinking that was what might be throwing off the static tracking.

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02-21-2013 10:00 PM  5 years agoPost 11
RM3

rrElite Veteran

Killeen, Texas - USA

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I'm not sure why your more concerned with the static tracking vs dynamic in flight tracking....

if the blades track strait at operating HS during upright and inverted hovering then there is probably nothing wrong with the head....worn dampeners on the other hand are a no no if you value keeping the tail boom attached the frame and want smooth rotor operation.

the vibs that cause sideways tail shaking can come from anywhere there is a loose frame point or out of balance or out of alignment rotating item....

showing a preference will only get you into trouble, 90% of everything is crap...

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02-21-2013 10:10 PM  5 years agoPost 12
helixangle

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Mamaroneck, NY - USA

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for purpose of illustration, the motor is static

the first photo shows run-out "left to right" on the fan hub, second photo shows run-out "left to right" on the clutch disc, i fully understand the mechanics of a conical compression hub, my question...

where in this scenario do we use the foil, and how does it affect the placement of the clutch without having affected the hub, I guess my statement would be you would have to be at tolerance on both independent from each other without creating "the hula-hoop" effect

Be sure the juice is worth the sqweeze
Remember life is hard...even harder for stupid people

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02-22-2013 12:27 AM  5 years agoPost 13
flyinfriend

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North American continent

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RM3,

My in flight tracking is perfect. I was concerned about the static tracking because I had read that if the head block is messed up it would cause static tracking to be out. If the head were messed up it would be a source of vibes. I was wondering if 1 cm difference in static tracking is a lot for a gasser helicopter and if it would indicate the head being off.

I am trying to chase down a vibe that is causing the heli to drift very slowly counter clockwise. I can see the tail vibe and the heli turns a bit to the left and then it is fine until it happens again. It would probably take a couple of minutes for it to turn 360 degrees.

It also is affected by by head speed.

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02-22-2013 02:16 AM  5 years agoPost 14
Gearhead

rrMaster

Vt

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lets get things straight here, he said "1cm",, well 1cm is 10mm,,

so he must mean 1mm,,

1 mm is .040"

http://www.towerhobbies.com/help/convcalcs.html

Jim
Buzz Buzz Buzz

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02-22-2013 02:40 AM  5 years agoPost 15
Gearhead

rrMaster

Vt

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as for your blades being off, check your Flybar Control Arm (see link) it may be slightly bent

http://www.centuryheli.com/products...76SA&pageid=284

Jim
Buzz Buzz Buzz

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02-22-2013 02:45 AM  5 years agoPost 16
flyinfriend

rrApprentice

North American continent

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One blade is 1 cm higher than the other when I measure the trailing edge of the blade from the same spot on the ground and rotate the head 180 degrees and measure the other one. The flybar is locked.

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02-22-2013 02:48 AM  5 years agoPost 17
Gearhead

rrMaster

Vt

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edited
I would remove 1 blade and used a wrench to turn the Spindle to see if it's bent, you will see one or both Grips wobble as the Spindle turns

Jim
Buzz Buzz Buzz

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02-22-2013 04:22 AM  5 years agoPost 18
JKos

rrProfessor

Redondo Beach, CA

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You could check the spindle while swapping the blades.

Also check your flybar paddle alignment. When I had Predators, I found that they were pretty sensitive to paddle alignment. At least mine were. Although it usually also caused funny stuff with dynamic blade tracking.

- John

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02-22-2013 03:14 PM  5 years agoPost 19
chris6414

rrApprentice

Sneads Ferry, NC USA

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Have a Hawk and Predator and never static track blades. Only dynamic. Side to side vibe? Trying to picture that. Any occasional tail kicking is usually a tuning issue. A tad too rich will cause the tail to move side to side a bit while the motor is slightly burping in and out of 4 stroking. Most of the time you can't even hear it but a slight tweak on the LS needle and it will smooth out.

Century Hawk Sport, OS .32, Futaba 7C, GY-601 9251
Predator Gasser SE G-23, Fut 3010 servos, JR gyro/servo

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02-22-2013 06:57 PM  5 years agoPost 20
flyinfriend

rrApprentice

North American continent

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I haven't had a chance to swap the blades and measure, will do that tonight.

I did check my Spectra's static tracking, the blades are within 1mm of each other compared to 1cm on my Predator.

I'll swap out the blades and report back.

Thanks for all of the replies!

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