[Bdegan]

Hey everyone,

We have been posting in Tyler's Carden thread about the Hitec servo issues a few of us have been having.
I decided to start a thread on its own.

Here are 2 videos i took this evening of my servos.
My particular set up is 2 x 7950's on the ailerons, 2 x 7955 on the elevators and a 7980 on the rudder.

The first video is using 7.2 volt LiIon unregulated.
The servos do the normal chattering as the try to hold center. But there is visible vibration while they do this . The 7980 rudder servo would wiggle or oscilate ( the jitter ). The fact that I installed heavier tailwhell springs help to reign that servo in.

The second video is with A123 power. The servos still chatter as they try to hold center. But they don't vibrate half as much and the 7980 rudder servo won't oscilate or jitter.

On the lower A123 voltage, all the servos are still plenty fast, responsive and powerful.

Now I just need to get out and do a flight test to see if what i thought was flutter goes away.

Video 1 withunregulated LiIon

+ YouTube Video

Video 2 with A123

+ YouTube Video

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[FLYINCHASE]

wow brad. thanks for the post. thats kind o scary!!!! i've been using 7955's with 6 volts. changed to a123's this year. glad i didnt go 7.4v

thanks
mike

[wingburner]

WOW!!!!...

[Tyler P]

Originally Posted by wingburner

WOW!!!!...

LOL. You hinting at Spektrum servos, Jack?

[flyloose]

O.K, maybe I'm just a bit dense...but I didn't find the Lion test that bad...If the constant hunt for center is a concern have you tried maybe just opening up the dead band a bit?

Now, I'm not trying to discount any issue you might be having....If you're noticing flutter than something must be going on. It just doesn't seem like there's a whole lot going on there. What about the durant drive system...Is there more slop with that compared to a traditional pushrod setup?

Interesting thread...

Thanks, Eric

[Tyler P]

Hi Eric,

We've all been having issues with the 7950s, hence the thread. Brad and I have both experienced flutter on our new planes but there doesn't seem to be any good reason for it.

The 7950 seems to have a bad reputation for bad jittering on lipos and it will actually manifest itself as flutter in the air.

As for slop in the Durant system, no. The only slop that is even possible is if the gears in the servo have slop. The Direct Drive is just that, direct. No linkages or anything to develop slop.

I'm going to try and drop mine down to 6v and see what happens.

Tyler

[Tyler P]

Lol. You've got it good with yours Brad! Mine is jittering way more than that on LiPos. The one aileron and my rudder shake like crazy! Yours are barely moving in comparison!

I hope Hitec provides a fix of some sort. I want to use their servos but not if it causes one of my control surfaces to blow off!

[dirtdr]

so is this issue limited to the 7950 and 7980?

i have been running 7955's on unregulated lipo this year and so far no issues.

[Bdegan]

Hi guys,
You are correct, there sin't much movement going on. The difference is a noticable between the two voltages. But I am not getting anything compared to the jitter some of the guys on flying giants are getting.
Some of the videos I have seen are absolutely outrageous.

Tyler, my rudder is only behaveing because of the really stiff tailwheel springs.
If i unhook the springs, the rudder starts to oscilate bad enough the whole back of the plane starts shaking from side to side
( Can we say ... tail wagging the dog LOL )

I have a 7990 coming ( with the new magnetic encoder ) to try on the rudder.

I noticed last night that one of the cells in my A123 packs drops its voltage faster than the others. They are a few years old andhave been in a few different planes. They are great for bench testing stuff.
But I won't trust them to do a couple of test flights.

So now my delema is ..... do I get a couple of new battery packs?
A123 or LiFe...

Or...

Do I get a regulator likethe smartfly one to plug both of my LiIon packs through, or 2 individual regulators.

Batteries or regulator ?? Which route would you guys suggest ?



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[Bdegan]

Originally Posted by dirtdr

so is this issue limited to the 7950 and 7980?

i have been running 7955's on unregulated lipo this year and so far no issues.

Its pretty much isolated to the 7950 and 7980.
Some guys are claiming they are having issues with the 7955's. But the reports are very few and far between.



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