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Home✈️Aircraft🚁Helicoptere-AlignOther › TRex 450 Vertical Fin flapping like a Hummingbird!
10-28-2006 01:23 AM  12 years ago
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Rockohaulic

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Canyon Country, CA, USA, 3rd Rock from the Sun

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TRex 450 Vertical Fin flapping like a Hummingbird!
I've seen vibration issues before, but what would make the vertical fin vibrate like a hummingbird on crack?

I would think it couldn't be the main blades, they wouldn't vibrate at such a high frequency would they?

And last time I checked the tail blades balanced nicely... And if they were out of balance, wouldn't they affect the horizontal fin more???
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10-28-2006 01:31 AM  12 years ago
caseyjholmes

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Portland, Oregon

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balance the blades while on the heli.

FIRST: be sure your paddles are glued on and secure!

CAREFULLY spool it up to half throttle in your hand and feel the side of the frame for vibration. If it is vibrating the tiniest bit, you can work it out with tape on one blade or the other.

When you can spool the heli up in your hand to half throttle and there is no vibes, the tail fin wont shake. Make sure your tail blades are balanced on the the heli as well. Balancing them off the heli doesn't do much good, as the heli could have a .01mm machining tolerance difference from one main blade grip to the other.

To balance the tail:

remove main blades.
spool heli up to 1/4 throttle
if any shakes, add tape to one tail blade (and paddles!) or the other untill it's gone. (do this to the paddles before tail blades are installed as well)

You'll have to do this with each crash, and each new set of blades and tail blades to get ALL the shakes out of the heli for good. a crash can cause a minute warp in the rotor head block, unoticable by human eye, and this will cause a slight wobble throughout the whole heli. the fix is to balance the blades after they have been installed. I recently learned this from some sponsored pilots at a local field..
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10-28-2006 06:17 AM  12 years ago
xj10bt

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Gainesville, FL

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Are you out of your freakin mind?
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10-28-2006 01:49 PM  12 years ago
Rogan

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Houston, Scotland - UK

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Check that your tail blades aren't damaged - busted tail blades or a bent tail shaft cause those high freq vibes. Screwups in the main section are much slower, larger oscillations.
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10-28-2006 02:21 PM  12 years ago
rudyy

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E. Amherst, NY

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I have this problem before. My tail fin vibrated like the end of the world. Check your tail shaft. It could have been bent.

Rudy
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10-28-2006 02:58 PM  12 years ago
ckoelliker

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St. Simons, GA

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I had the same problem and it took me forever to find it. It was the new tail hub. It was somehow defective. I finally changed it back to the old one and it solved the problem. Point being that it could be a number of things from bad bearings to bent shafts. Try the most likely things first and then keep looking.
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10-28-2006 03:07 PM  12 years ago
rudyy

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E. Amherst, NY

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Actually, for my case, I end up upgrading the whole tail assembly to metal as I was never able to find the problem.

Rudy
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10-28-2006 04:28 PM  12 years ago
caseyjholmes

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Portland, Oregon

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Are you out of your freakin mind?
No. this is what it takes to get a completely vibe free Trex some times.. Does that seem like too much to you? Perhaps I am being a bit picky, but I like to fly helicopters that have been well set up..
I know it's not a good idea to spool up a heli in your hand, but if you want the vibes gone, you'll need to find some way to do it safely.
You might wanna contact boid about borrowing his patent pending foo shield if you don't think you can handle it in your hand with/without the blades on..

He may even be willing to share his chili con carne recipie, but who knows
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10-28-2006 04:48 PM  12 years ago
helimatt

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Lafayette, IN

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My X400 had this problem as I was setting it up (no bent/worn components) Balancing the tail rotor completely solved it.
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10-28-2006 06:06 PM  12 years ago
dave blackburn

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seattle

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I do the same thing.
Using small pieces of tape on the tail blades you can make your heli totally vibration free. You will be suprised how much better it flies and how much gain you can get on your gyro.
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10-28-2006 09:23 PM  12 years ago
electricdurango

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Sterling, VA

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If you fire it up in your hand hold it over your head. This will prevent the possible blades flying off and impailing you eye sockets. You think heli flying is hard to learn. Try with no depth perception.
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10-28-2006 09:32 PM  12 years ago
caseyjholmes

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Portland, Oregon

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I hold it sideways. Anything that flies off is going to the ground or up in the air Do not try to rotate the heli in your hand when the rotor is under power, and do not do this unless you really need to. It is best to have a trustworthy friend either control the radio or hold the heli.

Also, do not spool up the heli to full throttle EVER when there is no blades on the heli. Be sure the paddles are glued on too, before attempting any of this. (you may over rpm and explode the tail with no load from the main blades on the heli)
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10-28-2006 10:59 PM  12 years ago
drdot

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So. California, Orange County.

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fwiw..

Gotta go with Casey on this..Dynamic balancing works wonders for little helis...If you think the rex is tough to balance, work with a Hummingbird or Hornet for a while!

john.
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10-29-2006 08:53 AM  12 years ago
steph

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Hampshire England

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The method that casey describes i use but i did get it wrong one day and i suffered
While i was checking for vibration on my century humming bird i was distracted and the blade hit my arm you should have seen the bruising on my arm and it hurt for days afterwards
That was from a humming bird
I once had my carbon blades on my raptor hit me in the leg on spooldown right on the bone that made me say a few choice words won't do that again
The world is round you can run but you will always end up where you started from
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