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Old Dec 30, 2011, 04:28 PM
Registered User
Canada, ON, Stouffville
Joined Nov 2011
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Help!
Setting the throw on the elevator

Hi All....

I need help with what is probably a simple thing.....But I don't see the solution.

I got a Nexstar EP, and I am trying to adjust the elevator throw. Here is the issue....
I turn on the transmitter and receiver and the servo goes to center. The Arm looks like it is perpendicular and centered on the servo. I then adjust the clevise so that the elevator is set to the center per the instructions.

Now the throw should be even...1/2" up and Down. But I am getting 1/4" up and about 3/4" down. So more throw down than up. It looks like the servo is moving the same amount in both directions...but this does not translate into even amounts of throw at the elevator.

DR is not set and neither is Expo...They should not have any effect.

Changing the EPA changes both up and down equally....

Any Idea's what I am doing wrong.

Thanks Steve
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Old Dec 30, 2011, 06:55 PM
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wolfewinde's Avatar
United States, FL, Clearwater
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See if the servo is moving when you give it up - that would push against the servo, down would pull. And make sure the servo arm is centered in the neutral position with the TX on

Wolfe
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Old Dec 30, 2011, 08:17 PM
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Wintr's Avatar
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Quote:
Originally Posted by sts41 View Post
The Arm looks like it is perpendicular and centered on the servo.
Perpendicular to what, exactly? It should be at 90* to the control rod, not to the body of the servo.
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Old Dec 30, 2011, 08:30 PM
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Moab, Utah, USA
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Quote:
Originally Posted by sts41 View Post
I turn on the transmitter and receiver and the servo goes to center. The Arm looks like it is perpendicular and centered on the servo.
The angle between the servo arm and the servo case has no effect on anything. To get equal throw in each direction the servo arm needs to be perpendicular to the pushrod regardless of the arm's angular relationship with the servo case. Also the pushrod should be perpendicular to a line drawn to the elevator hinge line where the pushrod connects to the elevator control horn.

Quote:
Originally Posted by sts41 View Post
Changing the EPA changes both up and down equally....
Are you sure about that? It would be very unusual. On most transmitters there is a separate EPA adjustment for each direction of travel on a given servo.

Another thing to check is to make sure the pushrod is not flexing with up elevator.

Larry
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Old Dec 30, 2011, 11:41 PM
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Originally Posted by Lnagel View Post
Another thing to check is to make sure the pushrod is not flexing with up elevator.Larry
Interesting comment, reminded me of something that happened to a friend many moons ago. His real life ultralight crashed on maiden (he was okay) because all adjustments were made from a static position, once in the air there seemed to be way too much slop in the controls with speed/air resistance.
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Old Dec 31, 2011, 01:05 PM
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eflightray's Avatar
South Wales U.K.
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A picture always helps.

Look at the elevator horn push rod hole to hinge angle, the servo arm need to be roughly the same.
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Old Dec 31, 2011, 06:43 PM
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Canada, ON, Stouffville
Joined Nov 2011
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Thanks all...I will try a few things once the hangover is OVER

I also had a few idea's on what to check...mainly the distance the rod is traveling...should be easy enough with a marker and some calipers...Check it connected and un connected to the horn...I will also make sure the horn was properly attached at the factory.


Happy New Year to all....

Steve
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Old Dec 31, 2011, 07:26 PM
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Quote:
Originally Posted by Lnagel View Post
The angle between the servo arm and the servo case has no effect on anything. To get equal throw in each direction the servo arm needs to be perpendicular to the pushrod regardless of the arm's angular relationship with the servo case.

Larry
That can't be right, surely? Imagine the servo arm has been pressed on almost inline with the servo,pointing forward to the nose.While the servo arm will move the same number of degrees each way if unattached,when connected to the pushrod the backwards movement will move the pushrod a considerable distance, but forward movement will not move the pushrod at all, it will just produce binding and stall the servo.this is an extreme example, but will translate whenever the arm is not at 90 degrees to the servo body.If I need excessive trim, I adjust the clevis and recentre the arm.Am I missing something?
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Old Dec 31, 2011, 10:53 PM
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Moab, Utah, USA
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Originally Posted by alibongo View Post
Am I missing something?
Yes, you are missing the part where the pushrod is perpendicular to the servo horn. It will not be in your scenario.

Larry
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Old Jan 03, 2012, 09:51 AM
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Ok...after re reading the manual for the Radio...there is indeed a way to change both of the throws independently...It just wasn't very well explained in the manual.

I now have everything set to the manufacturese recommended settings, and I Thank everyone for the help.


Steve
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Old Jan 03, 2012, 10:02 AM
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Latvia, Ventspils pilsēta, Ventspils
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Quote:
Originally Posted by alibongo View Post
That can't be right, surely? Imagine the servo arm has been pressed on almost inline with the servo,pointing forward to the nose.While the servo arm will move the same number of degrees each way if unattached,when connected to the pushrod the backwards movement will move the pushrod a considerable distance, but forward movement will not move the pushrod at all, it will just produce binding and stall the servo.this is an extreme example, but will translate whenever the arm is not at 90 degrees to the servo body.If I need excessive trim, I adjust the clevis and recentre the arm.Am I missing something?
Think you missed the point ... lnangel is 100% correct - servo arm should be perpendicular to CONTROL ROD / LINK to surface to get full proper movement.

Centre servo ... centre surface .... then place arm on servo with arm at 90 deg's to rod / link. Servo doesn't care what angle arm is as long as SERVO is centred at centre surface ... it then travels both ways without problem ...

I'm having trouble geometrically imagining your example ...
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