450 Bit of a wobble

[treff]

Hi all, I'm experiencing a small what I can only describe as a wobble. The wobble is vertical from tail to nose and not side to side on a FBL align 450 head. So far I have changed the main shaft, main and tail drive also the drive box. I have changed feathering shaft.
Sorry I can't do a video at present camera away being repaired. The wobble comes and goes and is worse flying slowly into wind. When I fly fast and steam around there is no movement at all. I have also changed the main bearings. I Do not think its head speed because
because it happens also in IU. I am at a bit of a loss. The heli as yet to be crashed so what ever it is is down to wear I think. I could fly on I suppose until something breaks or becomes apparent but is anyone as any idea it would be most welcome. Thanks

 

[Admiral]

I had a wobble like that a while back, it was an issue with the elevator servo having a partly stripped servo arm, only happened in a hover. I'm now more cautious on the parts I recycle after a crash.

 

[murankar]

Only thing I can think of is gains on the elevator. Its possible you may need to adjust the advanced settings gains. Gains may not be high enough.

Sent from my LG-E980 using Forum Runner

 

[treff]

Thanks guys for the quick reply and info. I will check out both tomorrow and get back. I've had this for some time now but have not been able to trace the fault. Thanks

 

[Lee]

Check for any mechanical slop in the head Treff.
From the servos all the way to the blade grips.
Make sure nothing is too loose or too tight.
If thats OK then as Matthias said, maybe you need to up the Elev gain by a few %

 

[treff]

Hi Lee, Hope your having a good day. Just been out and did a test with different gains on the 3gx and its not that. It comes and goes to much. The head is really good but I noticed there is a squeak developing and the blades no longer
are smooth in rotation . Not stiff but not smooth if you get my drift. I have changed the bearings and main shaft so I can not think of anything else.

 

[danhampson]

It does sound like a bearing causing vibes. Have you had a look at the owb and motor bearings?
I had the same sort of problem late season when my moor support bearing went bad

 

[treff]

Thanks danhampson in the process of striping it down now but I can see nothing really wrong except the main shaft is score at the bottom bearing and when I removed the head there is a tight spot when I
rotate the shaft. The motor is smooth to turn when the main gear is removed. I am beginning to suspect the oneway bearing but I can see nothing wrong. The tail and belt turn very smoothly and all the servos
are smooth and working. I will look again tomorrow. Bit of a mystery. Thanks

 

[pvolcko]

Also could be low head speed. What throttle value is this hovering in?

 

[treff]

Thanks pvolcko for the reply. I do not think it is head speed because it as been okay for the last 12 months and it's been flying okay. Even when I use IU with 100% throttle
it is still the same. I have pretty well replaced everything apart from the belt. I'm on my 7th strip down and it is still the same lol. Oh well.

 

[pvolcko]

May be bad dampers if not headspeed. Especially if it has developed after that kind of time and you haven't replaced them.

 

[treff]

Thanks pvolcko. Replaced the dampers, first thing I did. I've ordered some more main shafts just in case the one I put is bent. I don't think it's that because the wobble would be there all the time.
I've striped the thing right down now and doing a rebuild so we will see if that helps any. I also stuffed my other 450 into the ground today. Complete dumb thumbed it into somebody's back garden.
Thank goodness there was no one there. Complete right off. Got around into their garden and the battery was on fire but it had come off the heli. I will not be flying in the roadway again frightened the life
out of me. Bad day at the ranch lol

 

[murankar]

While it's apart clean, check and re oil all the bearings. Since your doing maintenance check over everything for proper operation.

Sent from my LG-E980 using Forum Runner

 

[Graham Lawrie]

I have read of the belt causing vibration and some people apply a spray to help lube it? The score on the main shaft cant be right and there should be no tight sections with the bearing. Put the old shaft on a drill and spin it. Sometimes the bend on shafts is so slight you cant see it with the eye.

I normally use the drill method or a really good steel engineers rule.

 

[treff]

Thanks murankar and Graham Lawrie. Yes I'm coming to the end of these helicopters now. I find with more experience I am flying faster
and pulling more g so the weak points are showing on the cheaper helicopters or rather now helicopter singular after killing one off the other day.
I also need somewhere desperately to fly, in the road is now a no, no after what happened. I was very lucky but some one could have been
badly injured. I find on this helicopter that the drive wheel to the tail drive does not line up properly running on less than 50% of the drive
so something is not right and I do not know what to do about this. Any ideas will be gratefully received. Thanks

 

[murankar]

Yep, maintenance is going to be your next learning objective. Now that you have progressed this far you will need to start scheduling you cleanings and oilings.

Also you might want to start saving for a true align or maybe some other 450 that is more durable.

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[treff]

Thanks murankar. Yes think your right. Stripped down and I find the belt beginning to shred so what's going on there I do not know.
I have cleaned every thing replaced the belt and main shaft, one way bearing and the tail drive plus all the rest I have done and now
the rebuild begins Thanks

 

[murankar]

The belt is going to shred over time. Its just something you need to keep am eye on.

Sent from my LG-E980 using Forum Runner

 

[treff]

Thanks again murankar. I have now changed everything on this 450 and I mean everything. Rebuilt it and it is pretty well behaving the same. It flies okay when there
is no wind but the slightest of head or tail wind and it starts to nod. The stronger the wind the bigger the nod. It's like it is flying on a very rough road full of cobbles.
This will go on for a few second then it will stop to begin again. So I think it is time to get out my gliders and go and do some relaxing flying. Thanks