Rjx 50 '09 - mutz nutz!!

[Backdraft]

(Quote) One of my mates has just got an X90 and he's had problems with vibrations.

Thats a bit unfair, "all the X90's in the club suffer from vibrations."

[RafeyRJX]

OK, so, new pitch spindle/main shaft/damper rubbers (well lubricated) tail shaft, reduced tension on the tail rotor drive belt, new tail blades. Everything carefully balanced, new main shaft bearings and if the engine ran any richer it would be Donald Trump not an OS!
Vibration is now at acceptable levels (head speed 1750rpm) - for an X50 that is. Though still noticable and causing the gyro (spartan ds760) to work a little harder than it should. Raise the head speed towards 1900rpm and it seems to settle down but its only an optical illusion as everything that isnt firmly fixed down is cheerfully eating itself!....... sorry, forgot to mention, new bearings etc and clutch bell etc.... oh and new cf flybar paddles. OH yeah, and flybar!!!!!!!!!!!!!!
~polishes favorite sledge hammer and eyes the silver behemouth with squinted eyes and a sage but knowing nod~ - it has until sundown on Saturday

[RJX HOBBY]

Hello,

could you tell me in witch way or where you see the vibration.
The heli does not vibrate from his design.o there is a reason for it.

BEst Regards
Frank
RJX HOBBY

[RafeyRJX]

When viewed from the rear, you can see the landing skids litterally wobbling from side to side under the heli. The resulting vibration causes the heli to pivot around the main shaft, here's the real head scratch - somtimes its clock wise and sometimes its anti clock!..... I've up graded my gyro and now fly with a Spartan 760ds. In HH mode it can keep the heli straight, but in normal it struggles to stay in control. If you see my last post re all the new bits, some of the ones i replaced (main shaft) we're already new. The vibe has almost gone now, but the first 'new' main shaft was 5thou out so not straight from new, and ive added an extra bearing block between the upper two on the main shaft. I pressed a 10mm deep bearing into a spare bearing block and fitted it in.
I would love to find a cure as i really do enjoy flying these helis, i have two for flying and a third airframe that i want to fit into a scale fuse - once in forward flight/stunt the machine really does perform and i wouldn't and cant question its ability. Just vibes driving me nuts.

[RJX HOBBY]

Hello,

so what you got is a wobble not a vibration.
What head speed you are running?
Wobble can be at headspeeds from 1500 to 1600 due the hard dampening.
Also important is that the dampners in the head are greased and you can turn the spindle with easy.

Best Regards
Frank

[RafeyRJX]

Thanks for the reply - dampers well greased, head speed is 1750rpm in normal flight mode with 1850 in idle up 1, i've thrown Idle up two in to my Tx with 1950rpm head speed, but not sure how far to go. (I have already reduced 1 os50hyper to aluminium shrapnel through raising the head speed to get rid of the wobble)
Head speeds have all been tacho'd so i know they're pretty accurate.

[RafeyRJX]

As a quick question, what's everyone else running? It has been suggested that i should be aiming for 1900 and 2100rpm respectively in normal and idle up 1.
Any views on how much an OS50Hyper has left to give when running these head speeds. - Suppose i should mention optifuel 20 being used.

[simm0]

nice to see that (frank)gets personally involved on the forum and helps out trying to resolve the odd issue
well done frank

cheers craig simmons

[RafeyRJX]

I have to say, i am mightily impressed.

[RJX HOBBY]

Hello,

Rpm´s are ok.You can go as high as 2100 for hardcore 3D.
At 1750 there should be absolutly no wobble.
It has nothing to do with your gyro o gyro settings.This for sure.
Looks also not as a foulty or bent part.
It sounds more something is not going smooth.Linkage,bladegribs,Flybar.....
Hard to tell without seeing it.
Could you post on VIMEO a video (Youtube in china is bloqued )?

Best Regrads
Frank

[RafeyRJX]

As soon as we get a calm evening so there's no interference from wind etc, i'll try and post a couple of short vids. Open to comments from all when i do. Thanks everyone for your input so far.

[RafeyRJX]

Update- ok so it's not exactly calm out there this evening. But running head speed of 2000rpm everything seems fine. There's a twitch on the tail but i'm not worried about that. I'de like to be able to report that i've found the problem and have identified it - i'm sorry, i can't and neither can anyone at the club. I've replaced a whole load of parts and installed a custom designed & engineered beefed up bearing block with tapered thrust bearing. I'm not going to claim that i've fixed anything, mearly eliminated a few small engineering deviances on a collection of parts. If it manifests itself agian, i'll report back.
Till then, it's time to go inverted!

[RafeyRJX]

Vibration/wobble up date. Ok after nearly a week of nearly vibe/wobble free flying i've changed a few parts around and found the following:
Heli no 1 - although i had fitted a new main shaft it was indeed bent - in the middle! so that explains teh worn out main shaft bearings etc and heli no 2, the cluth bell had the pinion geat fitted off center - it was tracing an elipse (not the bearing - i removed it and checked the run out the pinion was pressed in at a slight angle)
So now we are vibe/wobble free.......... next problem..... chasing and sorting this problem out has meant i'm using straight cut main gears, which are rapidly getting eaten and Ross mod have no idea when the helical clutch bells will be available again!!!!!!!!!!!!!!

[RJX HOBBY]

Hello,

Please contact Kingcobra in the UK.They have your part in stock.
For any need parts please contact them wih the correct part number and you will have it in 1 day at your doors.

Best regards
Frank Schneckenburger
RJX HOBBY