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solentlife
Extreme 3D
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Joined: 30 Dec 2010
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Location: Latvia / UK

PostPosted: Mon Mar 26, 2012 7:26 pm
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Excellent news Kent ........

It's worth taking the old ESC and connecting up a Rx and some servos in the same ch's as you use on the 450 ... if you have a motor that you can also load the power side - even better.

I suspect that what you may have is the ESC unstable not only in motor control but in power to Rx causing Rx to supply unsteady power through the common bus to the servos ... maybe they are kicking or just faintly twitching as power is fluctuating.
It would only take a tiny twitch to start a 450 on a dance !
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Kent P.
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Joined: 26 Dec 2011
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Location: Prescott Az

PostPosted: Tue Mar 27, 2012 2:02 am
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Thanks solentlife,
That actually makes sense about the unstable power delivery. Maybe someday I'll try your little experiment and see if that is true. I had another question though. I noticed that there are no weights on the flybar. If I put those on will that make it more stable?
Thanks,
Kent P.
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Dumb Thumbs
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Joined: 01 Jan 2008
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Location: USA, N.J., Middlesex county

PostPosted: Tue Mar 27, 2012 9:00 am
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Re:weights
Yes, flybar weights will make her more stable. Some will argue that flybar weights slow down response, but that's only if you are flying hard core and banging sticks. Try the weights, what can it hurt.
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tombo242
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Joined: 04 Nov 2008
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Location: Santo Estêvão, East Algarve, Portugal. Now 82, but still feels 22.

PostPosted: Tue Mar 27, 2012 5:05 pm
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+1 on that D.T.

For a good stable hover you can't beat a pair of well matched weights on a well set up and balanced flybar and head.

Tom.
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Kent P.
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Joined: 26 Dec 2011
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Location: Prescott Az

PostPosted: Tue Mar 27, 2012 8:01 pm
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Thanks tombo242 and Dumbthumbs,,
I'll try that as soon as time will allow.
Cheers,
Kent P.
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Burgess
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Joined: 27 Mar 2012
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Location: Wales

PostPosted: Sun Aug 19, 2012 7:20 pm
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Hi Kent P.

I recently had a similar situation on my latest T-rex 450 SEV2 clone airframe. On which I've replaced the upper main frame with a pair of carbon fibre Sports frame sides, to try-out the so-called improved servo positioning.

The main rotor head assembly is sound with no lost motion in any of the bearings or links, the feathering shaft and the main shaft are both Align. Brand new zz series main bearings interference-fit in the bearing housings; the lower housing is a Hobbyking bearing housing which incorporates a thrust bearing.

Situation: vibration transmitted up the main shaft from the Main Gear Set.
I had fitted an old main gear set, with a brand new Shaft Ring. The manual recommends not to over tighten the lower main gear set collar screw (Jesus bolt) so there was some teeter movement in the autorotation gear and similar in the main gear; and some clearance between the shaft ring and lower face of the thrust bearing.

On stripping down the main gear assembly found that the one way bearing shaft was worn at the area of contact with the upper end of the one-way bearing needle rollers. So in effect the shaft was deformed to a slight conical shape, that plus the clearance above the shaft ring allowed the main gear to teeter about whilst rotating, so when the throttle approach 50% the necessary resonance was propagated up the main shaft.

By replacing the one way bearing shaft and adding a shim to the shaft ring eliminated the excessive clearance and no more bad vibrations.

So the inferences drawn:
Whilst you eliminated the pulsing propagated by the old ESC, there is probably some clearance at the shaft ring. If you can teeter the main gear whilst in situ, then there probably is.

So, with the motor pounding out the rhythm, the main gear picked up the beat and rotor head simply got in the groove and the heli shook its booty.

Drop out the main gear assembly and check its assembly,
ensure that the top of the shaft bearing and ring aline; and
check that the bearing shaft in fully engaged in the autorotation gear.
Check there is no vertical free-play main shaft to top bearing, if so reposition locking ring.


Burgess
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crasher47
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Joined: 14 Feb 2013
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Location: Hawaii

PostPosted: Mon Jun 02, 2014 11:06 am
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One thing that made a significant difference in smoothness and stability on my HK 450GT was a set of Align 325 Carbon rotor blades. These weigh 61 grams per set ...heavy but they made a very noticeable difference as I noted. They are very well balanced from the factory andtrack very well, no need to do anything to them.
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