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Old Dec 29, 2014, 08:50 PM
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leadfeather's Avatar
Joined May 2006
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I implemented a push rod for the first time on the stab of a Fusion. The idea was to see if I could get full 90 up, and also get the typical +-30 movement of the stab at low rates. Seems to work fine...at least on the bench.

I used a similar technique as Ive used on flying wings to get full 90 up for multiflips. The idea is that the servo is not centered when the stab is. This offset in the servo position allows greater movement in the stab up direction. The trade off is that only upright multiflips will be possible.

By moving the pushrod to a lower hole on the stab control horn, I might be able to get greater down movement too for inverted flips, but it would be at the cost of resolution during regular flying. I'm not sure it is worth it to me personally.

To set the pushrod up I did the following:

1) Servo full up position then power off so it stays in the full up position.
2) With the stab in the 90 up position, make the pushrod to fit this stab and servo position. This guarantees full 90 up.
3) Power up the servo, adjust subtrim so that the stab is neutral when the stick is neutral.

I'll probably have to add a small motor to the glider to be able to fly this beast this time of year and test out this stab arrangement.
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Old Dec 30, 2014, 12:19 AM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
764 Posts
I took delivery of some servo stretchers. Been too busy on other stuff but a quick test indicated that they work on some servos at least but not on others. I will check them out with various servos that I have and post the results here
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Old Dec 30, 2014, 06:35 PM
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Quote:
Originally Posted by VintageFan View Post
I took delivery of some servo stretchers. Been too busy on other stuff but a quick test indicated that they work on some servos at least but not on others. I will check them out with various servos that I have and post the results here
Looking forward to the results. When you state the servo stretcher did not work on some servos, does this mean the servos don't move at all, there is no stretching or that there is less than 180 stretching?
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Old Dec 30, 2014, 07:41 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
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Less than 180 stretching.
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Old Jan 01, 2015, 04:02 PM
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I test flew the Fusion with the push rod set up for the stab and with the little motor added today. I was flying indoors to avoid the very cold air outside. Flew fine as expected. I didn't have enough height to safely try flipping. Once the weather warms up I'll fly outdoors and see if the flips are good...no reason why they shouldn't be.

The pushrod is the easiest set up for the stab and uses standard horns and a standard 9 gram servo.
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Old Jan 02, 2015, 01:33 PM
a.k.a Frank Campbell
Long Beach, CA, USA
Joined Jan 2007
764 Posts
Quote:
Originally Posted by leadfeather View Post
Looking forward to the results. When you state the servo stretcher did not work on some servos, does this mean the servos don't move at all, there is no stretching or that there is less than 180 stretching?
Not very encouraging. All the small modern servos I tried ran into a mechanical stop that prevented 180 movement.

The only servos that worked were old analog standard size servos and they were really slow.

The real killer is that the center is changed so that while you get 180 on some servos the center is not halfway. i will do a bit more investigation but it doesn't look promising.
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