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T-REX 550 › Head bobble
10-27-2012 04:30 AM  5 years agoPost 1
HeliNutAndy

rrKey Veteran

worcester, MA USA

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Hello,

I have a 550 that was crashed once about a month ago when I was getting the helicopter setup. I crashed from a height of fifteen feet or so. I replaced the main shaft, main blades, front tail gear(M0.8) which is slightly different than the stock setup) and the tail blades.

When I start to spool up the helicopter wobbles at a good rate until I hit a third of the stick and then the higher rpm seems to smooth things out. I also notice pretty severe wobble when the helicopter is on the ground and I drop throttle. What should I look for?

TIA,
Andy

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10-27-2012 06:00 AM  5 years agoPost 2
dkshema

rrMaster

Cedar Rapids, IA

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Wobble when you spool up or down is not uncommon, it's an indication that the rotor blades are not lined up where they need to be. Just slightly out of position, the entire head is grossly unbalanced. As you get to a high enough RPM and as the aerodynamic forces begin to take over, the heli will smooth out.

If it shakes badly in the air, and/or if the tracking is out and nothing will fix it, then you have something bent. One item you failed to mention in your repair list is the feathering shaft. You can pull the blades off, stick an allen wrench in one of the two bolts that holds the grips in place, then slowly turn the bolt (and feathering shaft) while watching the grips. If either one wobbles, even just a small amount, you bent the feathering shaft.

-----

But, until those blades get to flying where they want to be, you'll have some nasty wobbles.

You may need to also tighten your main blade grips just a bit, and as evenly as you can.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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10-27-2012 01:05 PM  5 years agoPost 3
HeliNutAndy

rrKey Veteran

worcester, MA USA

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Hi Dave,

I realize that you have pointed this out to me before but the wobble seems out of the norm. When I repaired the helicopter after I crashed I checked the feathering shaft and I did not notice any issues. If I can get a camera man(my son ) today I will try to get some video of what happens. Hurricane Sandy is on it's way and I need to get in some flying today.

Thx again,
Andy

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10-27-2012 09:38 PM  5 years agoPost 4
HeliNutAndy

rrKey Veteran

worcester, MA USA

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I tightened the main blades a hair and the wobble isn't as prominent and it is not there during flight. The helicopter flies really well now due to your help and I am not going to mess with a good thing Too be honest I am shocked to how well the 550 flies and I am looking forward to graduating to a larger helicopter. Winter is coming though

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