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Strange behaviour Jeti Assist rx and spool up..

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Strange behaviour Jeti Assist rx and spool up..

Old 08-06-2019, 12:37 PM
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Ceeray
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Default Strange behaviour Jeti Assist rx and spool up..

I have installed Jeti assist gyro setups into two different turbine models. Another is cb200 with rsat and rex6A.
another is rex 12A+rsa2.

both have shown similar symptoms. When spooling up from idle the flight surfaces may jerk uncontrollable very fast from time to time. And it does not feel nice in the air having plane twitching suddenly like it had hit a gust even in a no wind situation.
Both run Jets munt XBL series turbines.

Now I would like to know what causes this and how to fix it..
Old 08-06-2019, 01:56 PM
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wfield0455
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Originally Posted by Ceeray View Post
I have installed Jeti assist gyro setups into two different turbine models. Another is cb200 with rsat and rex6A.
another is rex 12A+rsa2.

both have shown similar symptoms. When spooling up from idle the flight surfaces may jerk uncontrollable very fast from time to time. And it does not feel nice in the air having plane twitching suddenly like it had hit a gust even in a no wind situation.
Both run Jets munt XBL series turbines.

Now I would like to know what causes this and how to fix it..
What firmware version ? This is just a guess but I seem to recall early Cortex gyros required a "hush blanket" I think they called it for turbine use . It was basically sounds damping material to prevent really high volume sounds from a turbine from affecting the gyros sensors... Perhaps the Assist is having an adverse reaction to some sound frequency the turbine puts out at certain throttle settings ?
I haven't had cause to use it yet but I think the Assist will monitor certain vibration frequencies and can filter them. Don't know the details but perhaps worth looking at this info and seeing if there is something going on a certain throttle settings, etc. I'm just guessing here but I think that is where I would start looking. If your Assists aren't already upgraded to V1.12 then I would do that as well.
Old 08-06-2019, 02:06 PM
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HarryC
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I had that problem with Weatronics gyro receivers in one jet model. The problem was acoustic interference. Mems gyros are not solid state, they are miniature vibrating mechanical devices and the vibrating part can be given a kick by certain sound frequencies, tricking the gyro into thinking the model is rotating and thus commanding the servos to oppose it. In the Weatronics it only happened, and always happened at certain engine rpms. The control surfaces would flutter and give some big kicks.
You can check to see if it only happens at certain rpms. If so, you could try using the Assists vibration logger to find where the problem frequencies are and use the Assists software to block them. If it does behave as acoustic interference I would also inform Jeti factory direct, as they need to be aware of it and use appropriate quality gyros and firmware that would not allow this problem in the first place.
Old 08-06-2019, 05:13 PM
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cartune
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Which surfaces? Does it have smoke?
Old 08-06-2019, 08:45 PM
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Ceeray
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Su27 tailerons were affected most and in Carf eurosport X axis took most twitches. No smoke. 1.10 fw, gotta put 1.12 in.

su27 crashed when started oscillating during landing and go around caused plane to eat dirt... big job to repair.
Old 08-07-2019, 03:39 AM
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cartune
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The reason I ask is I had same problem with jeti assist rec in a bvm plug and play viper with king tech turbine.it only affected tail servos. I found the smoke tube rubbing on turbine to be the problem. It would only do it on run up. Removed smoke tube and all went away. Hope you find your problem.
Old 08-08-2019, 10:55 AM
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Ceeray
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Today some tests with new 1.12 firmware (which also was not easily updated.. it failed and had to make a recovery for it).
All tests were done on the ground.
1. running engine throttle up and down -> causes glitches and random jerking. Sometimes full deflection. Very rapid movements.
2. Gyro/RX taken off from the plane as far as wires go (10cm) and held inside fist still to isolate the RX from plane fuselage. No difference, these anomalies still exist as earlier.
3. turbine throttle- and pump wires rerouted as far as possible from eachother, same tests as above. No difference.

Next test will be removing telemetry , that could cause a ground loop (from rx throttle to ECU to telemetry to RX), but I am pretty much going out of ideas whats causing this. And this same kind of behaviour in two different airframes, different engine sizes ( 200XBL and twin VT80 BL setup) and different rx setup (twin had CB200+Rex6A+Rsat2, Eurosport REX12A+Rsat2)

Something is really bugging JETI gyros now.
Old 08-08-2019, 12:47 PM
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jsnipes
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Suggestion: Install a Cortex Pro and be done with the issues until the Assist is more mature, ready, and proven to work in Central Box setups. JS
Old 08-08-2019, 01:04 PM
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wfield0455
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Originally Posted by Ceeray View Post
Today some tests with new 1.12 firmware (which also was not easily updated.. it failed and had to make a recovery for it).
All tests were done on the ground.
1. running engine throttle up and down -> causes glitches and random jerking. Sometimes full deflection. Very rapid movements.
2. Gyro/RX taken off from the plane as far as wires go (10cm) and held inside fist still to isolate the RX from plane fuselage. No difference, these anomalies still exist as earlier.
3. turbine throttle- and pump wires rerouted as far as possible from eachother, same tests as above. No difference.

Next test will be removing telemetry , that could cause a ground loop (from rx throttle to ECU to telemetry to RX), but I am pretty much going out of ideas whats causing this. And this same kind of behaviour in two different airframes, different engine sizes ( 200XBL and twin VT80 BL setup) and different rx setup (twin had CB200+Rex6A+Rsat2, Eurosport REX12A+Rsat2)

Something is really bugging JETI gyros now.
On the model with a CB200, did you simply try disconnecting, binding your RSat in default mode and connecting it to RX1 of the CB200 ? If you still get glitching with that setup then it's not an Assist problem.

In the model with the REX12A I'd simply go into device explorer and select Reset to Default which will place it in Assist Off mode which shouldn't be trying to stabilize anything. I'd also get rid of the secondary receiver and test everything in default mode (no dual path, no clones, nothing).

If those 2 tests don't completely eliminate the problem then I don't think it has anything to do with the sensors or even the Assist itself. Are you using the same type servos in both these airplanes ? I've heard of guys having issue with MKS servos on long extensions with Jeti but that has nothing to do with the Assist itself..

Last edited by wfield0455; 08-08-2019 at 01:45 PM.
Old 08-08-2019, 08:56 PM
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Ceeray
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I cn switch assist functions off and no problems after that.
Plane and rx work fine as long gyro portion is not activated.
Old 08-08-2019, 11:02 PM
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HarryC
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Originally Posted by Ceeray View Post
but I am pretty much going out of ideas whats causing this. .
I have already told you, it is acoustic interference. It is a well known problem with MEMS gyros.

Weatronic gyros suffered from it, Bavarian Demon used to and sold a sound proofing hood for their gyros until they fixed it. A couple of years ago when Jeti was still designing the Assist I asked Jeti if they knew about acoustic interference and how to avoid it, they assured me that they did, perhaps they didn't.
Old 08-09-2019, 12:13 AM
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Ceeray
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Looka like they botched it then. I will make a foam box over the rx and try it out..
Old 08-09-2019, 12:16 AM
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Its know in other gyros systems too, just put some fluffy Velcro across the top of the gyro and it will absorb the high frequency harmonic.
Old 08-09-2019, 05:13 AM
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But, if it was high frequency acoustics, then shouldn't test 2 that Ceeray performed (holding Rx in closed fist away from model) have provided sufficient dampening to rule that out, both mechanical and acoustic?

Paul
Old 08-09-2019, 05:33 AM
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Very easy to confirm, or not with the velcro, or as they say in the trade Hook & Loop :-)
Old 08-09-2019, 07:44 AM
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Originally Posted by JSF-TC View Post
But, if it was high frequency acoustics, then shouldn't test 2 that Ceeray performed (holding Rx in closed fist away from model) have provided sufficient dampening to rule that out, both mechanical and acoustic?

Paul
I would think it very hard to hold the gyro perfectly still in your hand especially with the engine running.
Old 08-10-2019, 04:08 AM
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jesse2357
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I have assist receivers in all my jets starting with an m70 all the way up to a jet central rhino 200. I don't experience those issues. I will say right off the bat I drop the gyro master gain to 34 and work up slowly from there. Maybe a pic of your setup will help identify anything else possible causing it. Does it do it if turn the gyro off?
Old 08-10-2019, 06:35 AM
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Ceeray
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Gyro off all jittering goes away. Rx works fine.
Today I tried with foam insulation box all around the RX. Jittering/chatter was still there but maybe not as much. Might be placebo effect too. But when I tried it airborne thr plane came silky smooth , with gusty wind not even a ripple. Like I was flying in a sticky soup, all movements and controls went mushy. No chance for second flight as nose gear pin folded on landing.. I would have dropped master gain to lessen the damping. Also new software inside rx so that also has changed.

i will report findings here.
Old 08-10-2019, 07:42 AM
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HarryC
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Originally Posted by Ceeray View Post
Like I was flying in a sticky soup, all movements and controls went mushy..
What % value have you got in stick priorities?

I would not fly it if you can still see some jittering. I came so close to losing a jet when the weatronic gyro flipped it inverted turning finals to land.

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