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Old Sep 05, 2008, 12:56 PM
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Trex 450 tail rotor pitch issue

I've received a so called "test flown" and "set up" Trex 450 from RC-experts in Hongkong.

Turns out that I have a problem with the tailrotor pitch: when the slider that governs the tailrotor pitch is about in the center of the tailrotor shaft, the pitch is in the "wrong" direction causing the heli to rotate.

Trimming it into the "correct" position, does not leave sufficient room for rudder movements. I'm stumped.
Does anybody have any ideas?
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Old Sep 05, 2008, 12:59 PM
LaurenceGough's Avatar
Reading, UK
Joined Sep 2007
6,371 Posts
You'll have to move the servo on the tailboom which will just slide when you loosen the screws. Remove all trim/subtrim and then tighten the servo up when the pitch gets to a few degrees blowing air to the right of the tailboom (looking from the back of the heli).

Tighten up, this should be good enough for a beginner to fly depending on the gyro, what is it?

Also make sure the servo horn is 90 degrees to the case (while not bending tail linkage) when there is no trim/subtrim. If it's a very little amount out do not worry, get it as close as possible.
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Old Sep 05, 2008, 01:24 PM
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p4ddy's Avatar
southampton uk
Joined Jun 2006
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WOW!!! i'm just amazed you got exactly what you ordered from them. I ordered an Airwolf fuse from them which was out of stock which they neglected to inform me & 2 months later the fuselage turned into a 2nd Trex 450 S kit (GF frame).

I think if i'm right you'll find that centre pitch isn't exact centre on the shaft. Mine seems to be more pitch available one way but it has no overal effect on my flying.

As above, although i'm confussed about the blowing?? lol
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Old Sep 05, 2008, 01:43 PM
LaurenceGough's Avatar
Reading, UK
Joined Sep 2007
6,371 Posts
Quote:
Originally Posted by p4ddy
WOW!!! i'm just amazed you got exactly what you ordered from them. I ordered an Airwolf fuse from them which was out of stock which they neglected to inform me & 2 months later the fuselage turned into a 2nd Trex 450 S kit (GF frame).

I think if i'm right you'll find that centre pitch isn't exact centre on the shaft. Mine seems to be more pitch available one way but it has no overal effect on my flying.

As above, although i'm confussed about the blowing?? lol
Lol, well at center arm travel the tail blades should be pushing air to the right to counter main torque effect in a hover of the headspeed you normally fly at.
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Old Sep 05, 2008, 02:19 PM
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Maryland
Joined Nov 2006
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There is nothing wrong with using subtrim on the rudder channel to get the servo arm at 90 with most gyro's. The 401 for example....when it initializes, it will simply recalculate this as the new center position.

Also, you don't need to have any pitch with the slider at center. The gyro will counter any torque....

Watch the Finless vids, he informs you to mechancially center the slider in rate mode (which will give zero pitch at center), then fly in HH mode.

Good luck,
Skarn
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Old Sep 05, 2008, 03:04 PM
LaurenceGough's Avatar
Reading, UK
Joined Sep 2007
6,371 Posts
Quote:
Originally Posted by Skarn
There is nothing wrong with using subtrim on the rudder channel to get the servo arm at 90 with most gyro's. The 401 for example....when it initializes, it will simply recalculate this as the new center position.

Also, you don't need to have any pitch with the slider at center. The gyro will counter any torque....

Watch the Finless vids, he informs you to mechancially center the slider in rate mode (which will give zero pitch at center), then fly in HH mode.

Good luck,
Skarn
It'll work fine for basic stuff without but you need to set up gyros such as the 401, 2100T in rate mode, you don't need to on higher end gyros.

Bad experience using sub trim, I used to but it creates more problems than it's worth, it simply doesn't matter on the tail. It's actually best to have it off centre a little at mid stick/no trim.
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