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Joker › Help, Joker Vibrations
12-06-2004 05:16 PM  13 years agoPost 1
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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Hi all you joker flyers, Please Help.

Got a vibration and it's not a good one! Flys beatifully and all the blades including tail have been balanced but as the revs rise through about 1400rpm the vibration is awful. So long as I keep the revs down she is smooth as silk but should I rev up for aeros there is a horrible vibration. Seems to be harmonic but please give me your ideas.

Joker CX
30 3300gp cells
24-5 motor
Schulze 32-55
NHP Razor 680mm blades
stock tail blades

electric chopper nut (bit mad actually)

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12-08-2004 03:26 AM  13 years agoPost 2
bell-230

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sonoma, ca (currently milano italy)

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did you check the cg of the blades? and if the cg from left to right is same on both blades then check the cg on the chord. i just had to send in a pair of blades that where the exact same weight, cg, cg on the chord was off though and i had to send it back.

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12-08-2004 10:59 AM  13 years agoPost 3
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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help

Thanks bell230 I will try that. I have checked the cg on the span and that was fine. How did you check the cg on the chord?

Thanks for the suggestion.

Chris

electric chopper nut (bit mad actually)

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12-08-2004 02:57 PM  13 years agoPost 4
bell-230

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sonoma, ca (currently milano italy)

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eh,
the cg on the cord was a pain!
you basically have to find the balancing point on the blades, place a tube on the center of the blade and just keep moving it until it is balancedand measure it to find that paint it was balanced and check between the two. another thing you could do is just find a different set of blades from one of your friends and see if the vibe goes away. and if it does! just send em back i'am sure the manufacture will replace em if you explain.

and it helps to find a rod/ tube that isnt very slipery.

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12-09-2004 10:26 AM  13 years agoPost 5
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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Sounds like a right pain indeed. Ho hum, back to the bench!!!

Thanks again.
Chris

electric chopper nut (bit mad actually)

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12-09-2004 05:33 PM  13 years agoPost 6
thangd

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Sparks, NV

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I had the same problem on earlier days of Joker. This was on the Joker CF, remember the one with aluminum frame and boom. I can only get it to spin up to around 1350 RPM until the pod would vibrate. Anyway the problem was the two bearing on the main shaft. When I installed it was very tight and I had to force it on to the shaft and I end up hurting the bearing. After I replace that two bearing, then it would be fine. I was running a 24-4 on 32 cells and 24 tooth pinion. 1600rpm easily.

Thang

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12-10-2004 03:35 AM  13 years agoPost 7
GMcNair

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Birmingham AL

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Chris, I too have been chasing a vibration that is downright nasty because it is so elusive. Maxi, 1200rpm, 10s3p Tanic pack, Actronic ESC, 800mm mains, hovering at 5.5. The vibe manifests itself in the tail, and it's up and down and side to side. Slight vibe in the landing gear as well.

I turned down my 601 gyro gain, I Koll Rotor Pro'd and High-point balanced all blades/heads/hubs, checked each output shaft for true running, and I still can't find the gremlin. Thang, you bring up an interesting point. I purchased two used Maxi's, and in both, the main bearings are absolute trash. I figured it was because the previous owners bashed the mainshafts into them, because that's exactly what it feels like. On a sidenote, I pulled every bearing on the non-flying backup heli a couple weeks ago and ran them through my "Greaser", to do some prep work before I finish reassembly and get it flying. I was amazed at what little "stock" lubrication came out. Because of this, and my discovery tonight that the mainshaft bearings on my vibe-ridden heli were rough, I decided to pull all bearings on this heli and grease them. Each bearing had a scant amount in them. Very unimpressive. Every bearing I buy in the future will get a run through my Greaser first. I'll know if it was bearings tomorrow when the sun comes up and I test fly it again.

Now I've got a good reason to get the other heli flying...if it flies well, I can swap parts until I find the culprit.

Chris, just wanted you to know you're not alone.

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12-14-2004 01:11 PM  13 years agoPost 8
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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Joker Vibes

Thanks everyone.

Flew yesterday having checked the main shaft, swaped main rotors around, re-tracked. Just the same. Fine at lower rpms, smoooooth!. Turn it up 1 or 2%, ohmegod.

I'll try the main bearings although they felt fine when I had the shaft out but I will try anything once. I'va also got a new set of mains to try. Wish me luck.

And just for Gmcnair, I had to turn the gyro (JR401) down as well. Too high and it's just horrible.

Chris

electric chopper nut (bit mad actually)

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12-14-2004 04:49 PM  13 years agoPost 9
jeffscholl

rrKey Veteran

Whitefish, MT

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This is my suggestion.

Take off the mains and spool it up on the bench.
Make sure you secure the tail since the tail has incredible authority at high speeds.

From what you've described I think you will find the tail producing the severe vibrations.

Let us know what happens and we'll go from there!

Cheers,
Jeff Scholl
GravityShots.com

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12-14-2004 05:29 PM  13 years agoPost 10
GMcNair

rrKey Veteran

Birmingham AL

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Looks like my problem has been solved...appears to have been a tweaked t/r output shaft. I replaced it this morning, and the vibe seems to have left the heli. My test flights in 35 degree 15mph winds are a bit trying on me (I know Jeff, that's probably a warm summer day for you right now!) but despite the wind, I do think it's back to normal vibe-free flying. I am also replacing the t/r hub at the moment...after all, if the output shaft was tweaked, there's a slight chance the hub was also. I've got the part, might as well replace it now while I can. Back to the workbench!

Chris, pull your feathering spindle thrust bearings and make absolutely sure they are installed correctly. Ditto for your t/r thrust bearings.

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12-15-2004 12:37 PM  13 years agoPost 11
gpyros

rrKey Veteran

On a beach in Mexico

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Greg:

Great to see you found it!!!! Now get it flying and take some more pics!

China Greg

Maxi-Joker helicam
Joker-CX helicam
Graupner Jet Ranger (elec)
Raptor-50
Logo-10
9CH

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12-16-2004 10:37 AM  13 years agoPost 12
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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Joker Vibes

Thanks Greg,

Next jod perhaps, I'll run it up with no blades on first like Jeff's suggestion. Thanks Jeff. Duh, didn't think of that!!!!!!!!

Tail rotor shaft could be tweaked I suppose but it would have to be hanger damage.

Let you all know.

Chris

electric chopper nut (bit mad actually)

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01-07-2005 01:50 PM  13 years agoPost 13
Hobbywood

rrApprentice

Kerikeri Northland New Zealand

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Found the Vibes!!!!!!

Thanks everyone,

The Vibes were toooooo simple for me to check. The tail blades were causing all the problems. Perfectly balanced, perfectly pitched but horrible vibrations. Bought a new set of funky carbons, very pretty and they are GREEEAAAAT!!!!!!!!!!!!!!.

Thanks for the help and HAPPY NEW YEAR

electric chopper nut (bit mad actually)

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