Juddering servos on elevator - HELP

[woodsta888]

I have a raptor E820 and I have noticed that my servos are juddery when moving elevator. This transfers to the head visibly juddering. Moving Aileron they are smooth. I have taken off all linkage connections and all 3 servos with power off run smoothly. Power on they judder without being connected. There is no binding in any of the linkage from the servos to the swash. I have a set of voltmeter lights to monitor the Life pack for power and usually the light stays solid green. The lights now flicker to lower voltages and pulling aileron flickers to the last but only fractions of a second.

I have suffered 6 shutdowns in teh last 45 flights of 90 total - they last for a moment (1-2 secs) and the heli will spool up again albeit with a changed headspeed. And I'm concerned that this was caused by the BD3sx browning outt the 2 DSM2 sat recievers from these voltage drops caused by the voltage usage of these juddering servos.

Servos are Align 615's on an 800 heli and done 90 flights total so ~14 hrs. I can't fly 3D just sport and big air.

I havent plugged in the BD3sx to see if there are any changes but I was wondering if a low voltage could reset BD3sx settings where the swash settings have changed causing the judder.

Any ideas?

[woodsta888]

Here's a vid to show crunchy servos. Sorry about poor qualilty on old digital camera.

Crunchy servos - YouTube

[Ice-Man]

I Would say you have a dry joint or a bad connection in power supply not getting full power as your taking more than its giving or the battery has a dud cell

[helijohn]

I have a raptor E820 and I have noticed that my servos are juddery when moving elevator.

Probably what I am about to say won't apply but I had just this on a rudder servo. It was because it was a super servo and I had not told the gyro.

[woodsta888]

Changed LiFe for a new one, changed servos to HV decent futaba ones, removed switch, re set up the FBL unit from scratch and still got servo judder.

RC helicopter RAGE QUIT!!

CAn it be a signal from the FBL unit. THE BD3SX manual mentions this

Stepwise servo movementNo problem - this is the slower time grid (frame rate) in which some RC systems transfer their pulses.

With the faster frame rate of the device, this is merely more clearly visible on the servos.

I'd expect this to look very even in judder and be visible across the aileron movements aswell. This only happens when all three servos make any Elevator movement. Anyone know what stepwise servo movement loos like?

Any ideas? Think I may ask Bavarian Demon guys too.

[Guest]

Some jittery is normal for the demon on the bench, twitching, jumping and non linear as you are experiencing on the elevator, in flight it doesn't happen. What volt meter is that on the heli and what voltage is it calibrated too as with a direct setup not sure how that would work. Are you experiencing brown outs on this latest setup? Have you tried a 2s lipo setup?

This chap had a similar problem.

m.bavarianDEMON servos jittery - Page 1

MJ

[woodsta888]

Hi Maj,

They dont jitter when there is no input. They are still and silent. Aileron is smooth with no judder as is the tail. I have lifted the heli such as it would be in flight moving it around and the Mrs on the tx moving elevator and it still judders. Voltmeter is set at 6v cheap one but it just highlighted when there was lots of power draw. The elevator didn't judder when I first built the heli...............99% sure.

I haven't flown it yet, hopefully this evening.

BD got back to me very quickly and told me to run a seperate Rx with the loom and change my sat leads which I changed anyway. I have spare sats as I really struggled to bind one yesterday. No power into one of them. Saw it flicker once too.

One thing I still need to try is dual power leads into the BD3sx. My current connector between the LiFe and the FBL is EC3 split into two power leads. I think I can also put a second power 'in' where the data cable goes.

But i think the safest option is to bite the bullet and get a seperate RX and whilst I'm at it a 2s lipo. Hope Spektrum Rx's handle HV servos. Run a seperate power lead into both so that the rx deals with the power to the sats at a safer level. Though I'll be annoyed if the judder is still there.

I can't get it to brown out on the bench. lookin at my log book brown outs have occured on flight 4 of the LiFe pack cycle and I recharge the pack after flight 4. Goingback through my initial build Q's a member does say with LiFe that after 50% discharge there are problems. Maybe I can only get 2 flights from Life And should never draw down more than 1000 mah from a 2500Mah LiFe.

I think I'll pack the heli in the car and take it to an RC shop to try a receiver to see if it cures the judder though adding the receiver may keep the sats from browning out and the judder is fine. Just seems that judder will tax the servos and wear them out especially when they fight eachother across the swash which effectively they are solidly connected to eachother by. The Aligns I took off seem to have judder through a servo tester and I'm concerned that the resistance across the swash ruined the servos in teh end and I don't want that to happen to my nice expensive HV futabas.