RunRyder RC
 12  Topic Subscribe
WATCH  3 pages [ <<    <     1     ( 2 )     3     NEXT    >> ] 1117 views POST REPLY
Scorpion Power AlignRC
Four Stroker

Elite Veteran

Atlanta

My Posts: All  Forum  Topic

Well I will put my 2 cents in. First check the static tracking at zero pitch. This will indicate something bent - main shaft, spindle, head block, blade grips, blade roots. Could also be the rubber dampeners are not symmetric. Then carefully check blade balance.

Other than the obvious physical stuff, there is the electronic stuff mentioned above. Swashplate ? not my guess.

10-02-2016 05:17 PM
PM  EMAIL  GALLERY  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

tracking is as close as I can get it at zero.

did the tracking vertical hover, good.... inverted hover, also good.
Could also be the rubber dampeners are not symmetric.
explain? one harder than the other or longer or off center?

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

10-02-2016 06:56 PM
PM  EMAIL  GALLERY  Attn:RR
Dr.Ben

rrMaster

Richmond, VA, USA

My Posts: All  Forum  Topic

These things can drive you bat$hit crazy because you could have a never crashed but still mismachined part. Do you have a friend with a similar model with whom you could swap out the whole head assembly? In some cases, a whole subassembly swap is the only way to narrow and finally isolate the problem.

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

10-02-2016 07:01 PM
PM  EMAIL  GALLERY  Attn:RR
ICUR1-2

Key Veteran

Ottawa, Ontario

My Posts: All  Forum  Topic

have you balanced the head
I once had a kit with different weight of grips

spending time, paying attention

10-02-2016 07:22 PM
PM  EMAIL  GALLERY  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

you could swap out the whole head assembly?
I did... it had the metal Century FBL head... had the tail vibs, swapped it out for a Trex600 FBL head AND swash... same thing.
can drive you bat$hit crazy
already past that...

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

10-02-2016 07:32 PM
PM  EMAIL  GALLERY  Attn:RR
chopper37

Senior Heliman

FL350

My Posts: All  Forum  Topic

Swap out tail blades?

10-02-2016 07:54 PM
PM  EMAIL  GALLERY  Attn:RR
Gearhead

rrMaster

Vt

My Posts: All  Forum  Topic

so it's not the main rotor head, check the balls in the tail's thrust bearings, some of them could have flat spots on them, this could make one tail blade start to flutter a bit at a given RPM

Jim
Buzz Buzz Buzz

10-02-2016 08:40 PM
PM  EMAIL  GALLERY  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

Swap out tail blades?
check the balls in the tail's thrust bearings
will try/check that...
just finished checking the main to pinion mesh...its good, no tight spots.

would a OWB do it?... just weird cause the vibs are consistent...like they are "in tune" with the main rotor... but everything on the main rotor system is good. going nuts.

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

10-02-2016 09:04 PM
PM  EMAIL  GALLERY  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

OK this is weird...

decided to run it without the main rotor BUT leave the tail on with the tail blades...
I normally dont do this cause of the risk associated with holding such a large heli in hand while running even if it has no blades on it... but this is a last resort.

so

there is no vertical tail shake....
lifted the heli carefully into the air while running in Gov mode so HS is at 1800, no out of the ordinary vibrations and no vertical vibs...just the usual frame humming feeling you get on any nitro or good running gasser.

but when I reached to grab the tail boom with the other hand I noticed a bad vibration at the center of the boom... not at the base, not at the tail end... but in the middle.... right between the Torque tube support bearings...

the tail boom does not vibrate like this on the bench when spun with a dremel powering the tail drive gear to operating RPMs...

So here is my theory...

what if the torque tube if perfectly straight... but vibration from the engine causes the torque tube to rotationally oscillate like a jump rope inside the boom. (this is the circular vibs I feel)...but when the main rotor is introduced, the two resonate and shake the tail up and down? but when disassembled the tube springs back to straightness indicating no issue.

Im going to relocate the torque tube support bearings... I have an extra one so maybe will add another right in the center...

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

10-02-2016 09:44 PM
PM  EMAIL  GALLERY  Attn:RR
don s

Key Veteran

Chesapeake, VA

My Posts: All  Forum  Topic

If that doesn't fix it try different main blades.

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

10-02-2016 09:47 PM
PM  EMAIL  GALLERY  Attn:RR
Todd74

Senior Heliman

PA, USA

My Posts: All  Forum  Topic

On the bench, can you physically flex the boom up and down excessively? If so, check that your tail boom support ends are not loose on the ends of the tail support rods, thus nullifying the support they are supposed to offer.

My 600N rods usually have the ends come loose over time, allowing the boom to flex, and causing the exact thing you are describing, in a well running machine that has nothing bent or vibrating otherwise.

Solved by replacing the boom supports or securing the ends with JB Weld or drilling and installing a small screw through rod/end junction.

10-02-2016 10:36 PM
PM  EMAIL  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

ITS FIXED! I can now run into the 2000 HS range!

symptom: Tail vertical shake, in tune with head.

area of problem: Torque tube...

cause: Torque Tube is oscillating inside boom "jump rope style" between support bearings despite being perfectly straight when inspected. oscillation resonates with main rotor head.

solution: additional torque tube bearing support. TT now has three support bearings evenly spaced inside boom... apprx every 8 inches

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

10-03-2016 01:10 AM
PM  EMAIL  GALLERY  Attn:RR
xcellgasman101

Elite Veteran

WOODWARD, OKLA....

My Posts: All  Forum  Topic

Congrats!! XGM/VGM

John Crotts
www.soonerhelicamproductions.com

10-03-2016 01:35 AM
PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR
Slowpoke

Key Veteran

Dublin, OH

My Posts: All  Forum  Topic

mystery solved....great!

10-03-2016 01:48 AM
PM  EMAIL  GALLERY  Attn:RR
Dr.Ben

rrMaster

Richmond, VA, USA

My Posts: All  Forum  Topic

Out of curiosity, when there were only two bearings on the TT, were they equally spaced?

Ben Minor

Team Synergy Team Futaba Team Kontronik USA
Progressive RC

10-03-2016 03:03 AM
PM  EMAIL  GALLERY  Attn:RR
RM3

Elite Veteran

Killeen, Texas - USA

My Posts: All  Forum  Topic

the original G20 TT kit only had 1 bearing... after experiencing a TT snap in flight, between the support bearing and the tail gear so to solve that I added a second bearing support... they were not equally spaced. but since then I could only get up to 1800 on the head... then I went to from 640 blades to 696 and could only get to 1700 before the tail would shake (after extending the tail to a g30). but never had this problem on the belt tail.

now I have three as a solution... so there is only about 8 inches between them +- an inch.

Im surprised to find that this issue was caused by a resonance between the TT itself and the main rotor...despite everything being perfectly balanced and straight.

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

10-03-2016 04:11 AM
PM  EMAIL  GALLERY  Attn:RR
helifanatix

Veteran

Fountain Valley, CA

My Posts: All  Forum  Topic

That is just wonderful!!!

Thanks for reposting the solution. Looks like previously had a Sine Wave going on.

- Scott

10-03-2016 05:17 AM
PM  EMAIL  GALLERY  Attn:RR
rcheli808

Senior Heliman

Mililani,Hi-USA

My Posts: All  Forum  Topic

Thanks RM3,
I think I will try this on my Hugh 500D. In the pod and boom setup, the vibes(if any)are not that noticeable. But in the fuselage without the pod and boom tail support, it is very noticeable.
So Thanks again for that possible solution...

10-03-2016 06:39 AM
PM  EMAIL  GALLERY  Attn:RR
chopper37

Senior Heliman

FL350

My Posts: All  Forum  Topic

Great news, get out there know and enjoy it!

10-03-2016 11:42 AM
PM  EMAIL  GALLERY  Attn:RR
Four Stroker

Elite Veteran

Atlanta

My Posts: All  Forum  Topic

Yep everything has a resonant frequency and something has to stimulate it. As stated above the TT bearings should be unequally spaced to avoid the sine wave vibration thing. Are the tail boom AND TT BOTH straight ? Are the TT bearing supports off center ? Are the TT ends screwed up ?

But if it is fixed now don't worry about it.

10-03-2016 11:58 AM
PM  EMAIL  GALLERY  Attn:RR
WATCH  3 pages [ <<    <     1     ( 2 )     3     NEXT    >> ] 1117 views POST REPLY
Thunder Power RC ProModeler
 Print TOPIC Advertisers 

 12  Topic Subscribe

Saturday, December 10 - 8:49 am - Copyright © 2000-2016 RunRyder   EMAILEnable Cookies