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Old Jun 21, 2016, 10:41 AM
dnbarrie11 is offline
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Interesting Maintenance item

I build all of my planes with maintenance in mind. I use servo frames in the wings. I'm willing to sacrifice a few grams for the ability to swap a servo in a few minutes.

I was going through all of my planes in prep for Sacramento this weekend. On my X3 my left flap was showing some slop. Actual pushrods and kwik links were solid and solid on the servo and flap horn. WT F was causing this? I could see no shift in the servo.

Turns out the screws holding the servos down in the frames were loose. This was causing the servo to lift slightly. Tightened them and all is good. I used a small amount of Goop on the screws to serve as locktite but still removable.

Went through all of my planes and repeated the process. Most of the screws were loose to some degree. Even with no actual vibration in the airframes, we have to get them to and from the field in our cars. I'm sure over time this can cause things to loosen up. Obviously in my case.

Ready to go now!!

Darwin N. Barrie
Chandler, AZ
Team Futaba
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Old Jun 21, 2016, 11:19 AM
Dyno Don is offline
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Great tip!
Thanks
Dyno Don

Quote:
Originally Posted by dnbarrie11 View Post
I build all of my planes with maintenance in mind. I use servo frames in the wings. I'm willing to sacrifice a few grams for the ability to swap a servo in a few minutes.

I was going through all of my planes in prep for Sacramento this weekend. On my X3 my left flap was showing some slop. Actual pushrods and kwik links were solid and solid on the servo and flap horn. WT F was causing this? I could see no shift in the servo.

Turns out the screws holding the servos down in the frames were loose. This was causing the servo to lift slightly. Tightened them and all is good. I used a small amount of Goop on the screws to serve as locktite but still removable.

Went through all of my planes and repeated the process. Most of the screws were loose to some degree. Even with no actual vibration in the airframes, we have to get them to and from the field in our cars. I'm sure over time this can cause things to loosen up. Obviously in my case.

Ready to go now!!

Darwin N. Barrie
Chandler, AZ
Team Futaba
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Old Jun 21, 2016, 03:53 PM
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Guess all that buzzing after a hot charge can have undesirable side effects ...
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Old Jun 21, 2016, 05:15 PM
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You must.....

Quote:
Originally Posted by tkallev View Post
Guess all that buzzing after a hot charge can have undesirable side effects ...
Hey TK,

You must fly JR I was going to install a micro JR servo in all my open class planes just to let me know I had the thing on

Darwin
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Old Jun 21, 2016, 06:32 PM
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Hey hey hey....JR servos may be noisy, but there are good.
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Old Jun 21, 2016, 07:10 PM
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Sailplane landings would never cause things to come loose.

I'll take my 1000hz JR servo on XBus any day over those old pulse width servos.
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Old Jun 22, 2016, 08:23 AM
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Quote:
Originally Posted by mlachow View Post
I'll take my 1000hz JR servo on XBus any day over those old pulse width servos.
1kHz update rate? Wow, probably needed when you fly 11s speed runs .

Back to topic, an F3J pro told me that he regularly checks all servo screws (frames and also for the servo arms). For him, wooden servo frames also wore out too quickly, i.e. the screws loosing their grip in the frame.
These controlled landing crashes in F3J seem to take their toll on the material.

Reto
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Old Jun 22, 2016, 09:12 AM
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Quote:
Originally Posted by RetoF3X View Post
1kHz update rate? Wow, probably needed when you fly 11s speed runs .
No, just a compensation for old age. Modern radios have been wonderful in reducing the time for the stick input to get to the model. Good compensation for slowing of reflexes. It's strange that radios take a digital position, convert it back to a pulse width that then has to be measured and finally used to drive the servo. The pulse width stuff is 1960's technology when everything was analog.

While most non-powered sailplanes don't have vibration, there is still wear and the landing shock abuse. I guess the E-guys will need to check even more frequently .

If you land hard enough to damage a hinge line, imagine what you do to the servo mount. The usual solution is to tie the top and bottom skins together and add outboard bearings in the wings. That takes some load off the servo mounts, spreading it out a bit more. Cross tails are a separate problem. It's easy to apply a lot of force to the pushrod with a wide rudder or stab compared to v-tails.

Big surfaces, little light weigh servos, it's your tradeoff of weight vs maintenance issues. After a few years, the metal gears still need to be replaced and the hinge lines might need some CA, etc.


I guess the question is how many crashes, er, landings between screw tighenings. Were they just frames or did the frames also have outboard bearings?
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Old Jun 22, 2016, 09:59 AM
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Sounds like a perfect application for torque stripes.
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Old Jun 22, 2016, 10:56 AM
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building season is here.
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United States, OR, Silverton
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I use purple loctite and a small drop at that.
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