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HomeAircraftHelicopterAlignT-REX 700N › vibration issue
04-06-2010 11:21 PM  8 years agoPost 1



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My T-Rex 700n is fine at idle but vibrates spooling up for take off. My OS91hz has little over one gallon thru it. The high end is almost one and half turn out and the same for mid. This machine is very snappy except in 20 mph wind you have keep the head speed up. I also noticed during hovering my long tail rod vibrating like a blur. And the fuel slushes everywhere in the tank. I have dial indicated the clutch to .002" but did not bother to balance the G-Force Sho fan. Could this be the cause of the vibration? Or is it that engine is not broken-in yet?

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04-07-2010 05:00 AM  8 years agoPost 2


La Vista, NE.

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maybe the tail torque tube? If the boom is slid up too far the TT could not have enough room to float in there causing vibs - or if the TT bearings are not sitting right in those rubber cups? Just some thoughts along that line.

But a big one that I find all the time is the tail blades. Most sets I check are out of balance. A little packing tape to balance them and things run much smoother.

04-07-2010 05:56 AM  8 years agoPost 3



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how bad is the vibration is that vibe cause tail wag, i ve the same problem when the heli fly u wont even notice those vibe, and i consider its normal to have small vibe on the heli the vibe is generate by th engine it self, try increase ur HS if it getting worst it might be bad bearing, or the heli was not tune properly, just IMHO, about fuel slush i ve seen nearly all trex 700 got that..soo i consider it as normal due to high muffler pressure, get a header tank and u will be happy, or just get an omi megnet fuel clunk, the only problem is u wont get ur fuel tank dried to the end of ur flying if u not using header tank or magnet fuel clunk

Trex 600,700 AND 450, GY611, GY401, OS5H, OS91HZ, MGP, HS65HB, Scorpion 2221-8,

04-07-2010 06:17 AM  8 years agoPost 4


auburn ca

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sonny i would go through your whole tail drive and look for a problem.

you either have something very very out of balance on the motor but my bet is something in the TT drive tail area

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04-07-2010 06:47 AM  8 years agoPost 5

rrKey Veteran

South Korea

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+1, I'd check the TT for a bow. And that the TT bearings are seated well in the rubber cups. Check your gear train as well for an inconsistant whurring sound when your heli is spooling down. I've heard of a few kits that had out of round TT gears. How severe is this vibe? Could be as simple as a loose assembly somewhere. Good luck I hope you get it squared away...


04-07-2010 07:47 PM  8 years agoPost 6


Glendale CA

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Have you "epoxied" ur tail support caps???
it helps a lot.
the tail support rod's caps are secured with a 0.9mm screw.
remove them remove the plastic cap put some epoxy inside and mount them back on the rod.
dont forget to secure them back with the screw.

that really helps, give it a try

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