Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[kallend]

Telemetry test 3

First of all: Henrik, your calculation regarding the voltage at the (upgraded) stock servos is correct!

As many of you are concerned about the voltage situation at the (upgraded) stock servos, I did run another quick test to show what is happening with the voltage at the upgraded stock elevator servo in stall condition.

Setup:

Jeti Mui150 telemetry sensor soldered into the servo power line directly in front of one upgraded stock servo.
Both upgraded stock servos connected via the stock elevator cables and the MRC y-cable into one channel of my jeti rex12 receiver. Stock BEC directly powering the receiver. No Bluebox.

1: Both servos idle - no movement - voltage at the servo 4.9Volt.

2: Both servos running in servo test program on half speed. Both servos stalled by hand to zero movement.
Voltage at the servos in stalled condition: 4.3Volt.

What does the servo do when the voltage has dropped to 4.3V on account of being stalled? Does it return to center? Stay where it is? Something else? The servo's behavior is what (may) cause a crash.

[Evan D]

I agree with your post though it really isn't pointing to a specific root cause. I've pretty much done all of this.

One note is the 4.8V spec. In the old days of NiCad and NiMh batteries we used 4 and 5 cell packs that were nominal 4.8 and 6V. Most servo makers spec their servos when using these but I am not sure they really mean that the spec given is at the nominal 4.8 or the higher charged voltage. To be honest I really never concerned myself before because, as many things, I found that some manufacturers had numbers that didn't match my experiences. For example a JR servo felt stronger/ weaker than a Futaba with the same rating (don't want to start a JR/ Futaba war). When charged the batteries were much higher than 4.8 or 6V. And remember or systems work or supply voltage different than a battery would.

From all this I think a good thing to consider is upping the voltage from the BEC to 5.5 or MAYBE even 6.0V. Since the stock BEC is not adjustable this would require a different, why not 10A or higher, BEC.

But at a minimum we should consider a higher torque servo than the FW upgrade, stronger push rods, better/ shorter extensions, and going directly to individual slots on the receiver with a mix. Also I think everyone should swap the stab horns with as long a screw as they can use and glue the horn down, use better ball links on the better push rod with washers outboard of the ball as a safety incase they pop off due to the angle, and NOT have the elevator servo arm at 90 degrees to the fuselage but at 90 degrees to the push rod.

Again, this is my opinion

Thanks again Firebird. As I see it....Here is where we are.

1) The published min voltage spec for the MRC servos is 4.8V for the recommended operating condition.
2) Operation outside the ROC is not typically guaranteed by a manufacturer.
3) MiG drivers, yet, have no hard proof (video) that servos are stalled.
4) “IF” MiG drivers suspect servo stall is happening or could happen, it is up to us (not MRC) to mitigate and ensure servo stall doesn’t occur which will keep the servos within the published ROC.
5) MiG pilots most probably are aware of the flying style that might induce servo stall.
6) Stock wiring and servos are sufficient to operate the MiG w/o crashing as long as the ROC is not exceeded.

We must select the mitigation method of our choice.
- Flying style to ensure servos won’t stall
- Upgraded wiring and stronger servos if we intend to fly with a style which might induce servo stall

Pretty much up to us. If I were MRC, I might say something like...“Operating as to cause the ROC to be exceeded is not recommended. Operation outside the ROC may induce stresses which may impact successful operation.” In other words....not guaranteed.

Consider a car which you take to the drag strip occasionally to race. If you want the car to last, you will take actions to mitigate the extreme stress of drag racing. Common sense, if you want the car to last.

And....it now appears we need to avoid flying flaps down with high throttle/speed conditions.

We are getting a handle on the mystery! Bottom line, flight styles which might possibly cause operation conditions outside the servo ROC is at your own risk. It ain’t pretty, but that’s where we currently are IMO.

-GG

[t33jetman]

Mig-29, canopy opening modification.
It took me a week on how to make this work .
No 3D parts, no help, lots of cardboard and balsa and glue, and just old fashion gray matter and lots of coffee and sleep.

[Firebird]

Hello!

I like your test! One question for you :) - its possible to do a test with elevators connected to bluebox? I am interested in result with this stock connection(with bluebox). Thank you very much!
Even better 2 tests - stock servo extension with upgraded servos and upgraded servo extension with upgrades servos - both with bluebox connection. Thanks very much!

copied - test in progress

[Firebird]

Firebird - One missing data point.

What is the current/voltage when the servo is not being commanded to move and you apply a load in an attempt to move it? In other words, what are air loads doing to the stationary not stalled servo?

Can you post a link to the better cables?

-GG

Telemetry - test 5

Test 5 is showing the provided force (in gram) that both upgrade stock servos provide together, related to the voltage at the servos. Servoarms pressing against a kitchen scale is simulating aerodynamic pressure on the elevator in flight.

Setup:

Jeti Mui150 telemetry sensor soldered into the servo power line directly in front of one upgraded stock servo.
Both upgraded stock servos mounted over a kitchen scale with their servoarms equally applying force to the scale. Both servos connected via the stock elevator servo cables, connected via the MCR y-cable into one channel of my jeti rex12 receiver. Stock BEC directly powering the receiver. No Bluebox.

Find below the voltage at the servo with the related voltage at the receiver and the applied force in gram:


Idle voltage at servo 4,8 / volt at receiver 4,99 / force together 0 / force single servo 0 (idle)

volt at servo 4,8 / volt at receiver 4,97 / force together 1117gram / force single elevator servo 558,5 gram

volt at servo 4,7 / volt at receiver 4,97 / force together 1644gran / force single elevator servo 822gram

volt at servo 4,6 / volt at receiver 4,94 / force together 2746/ force single servo 1373gram

volt at servo 4,5 / volt at receiver 4,91 / force together 3417gram / force single servo 1708,5

volt at servo 4,4 / volt at receiver 4,92 / force together 3429gram / force single servo 1714,5 (maximum)

Note - one of the servos stalled during first test at 4,6volt, reversed it‘s direction and move to full opposite deflection and remained there not reacting anymore. After unplugging and reconnecting this servo - it followed all commands normally and the test could be completed.

unfortunately i can‘t provide current data with the present sensor as the amp draw is to little for the mui150 to recognize.

[kallend]

copied - test in progress

What does the servo do when the voltage has dropped to 4.3V on account of being stalled? Does it return to center? Stay where it is? Enter some kind of failsafe state (if so, what is it)? The servo's actual behavior is what (may) cause a crash.

A lot of force from the airflow on the stab is required to stall the servo when up elevator is applied. The direction of this force will not induce a dive.

If, however, the servo reverses that could be the problem.

[kallend]

Telemetry - test 5



Note - one of the servos stalled during first test at 4,6volt, returned it‘s direction and move to full opposite deflection and remained there not reacting anymore.

By "returned its direction" do you mean it reversed?

[Firebird]

By "returned its direction" do you mean it reversed?

Hello Kallend, yes - it reversed. Might not be the crash related as the other one worked normally and it did not happen again thereafter. But it doesn’t rise my trustlevel into this servos neither.

[GliderGuy]

Firebird - This is interesting data / very good data. Thank you for doing this. Need to evaluate what the implications are....especially in relationship to the voltage ROC of the servo.

Any behavior below the 4.8V is outside the ROC conditions and could be TBD behavior. I have no clue what servo circuit design margins are.

-GG

[kallend]

Hello Kallend, yes - it reversed. Might not be the crash related as the other one worked normally and it did not happen again thereafter. But it doesn’t rise my trustlevel into this servos neither.

Hmmm.

<Rolls eyes>

[Firebird]

Hello!

I like your test! One question for you :) - its possible to do a test with elevators connected to bluebox? I am interested in result with this stock connection(with bluebox). Thank you very much!
Even better 2 tests - stock servo extension with upgraded servos and upgraded servo extension with upgrades servos - both with bluebox connection. Thanks very much!

Telemetry - test 6 Bluebox

Test 6 is showing the provided force (in gram) that both upgrade stock servos provide together, related to the voltage at the servos. Servoarms pressing against a kitchen scale is simulating aerodynamic pressure on the elevator in flight.

Setup:

Jeti Mui150 telemetry sensor soldered into the servo power line directly in front of one upgraded stock servo.
Both upgraded stock servos mounted over a kitchen scale with their servoarms equally applying force to the scale. Both servos connected via the stock elevator servo cables, each cable connected to the related elevator position at the Bluebox. (No y-cable). The rex12 receiver elevator servo cable is connected to the Bluebox. Stock BEC directly powering the receiver. No other equipment connected.

Find below the voltage at the servo with the related voltage at the receiver and the applied force in gram:


Idle voltage at servo 4,8 / volt at receiver 4,98 / force together 0 / force single servo 0 (idle)

volt at servo 4,8 / volt at receiver 4,97 / force together 1127gram / force single elevator servo 563,5gram

volt at servo 4,7 / volt at receiver 4,97 / force together 1577gram / force single elevator servo 788,5gram

volt at servo 4,6 / volt at receiver 4,94 / force together 2545 / force single servo 1272,5

volt at servo 4,5 / volt at receiver 4,93 / force together 2741 / force single servo 1370,5

volt at servo 4,4 / volt at receiver 4,92 / force together 2908gram / force single servo 1454gram

volt at servo 4,3/ volt at receiver 4,90 / force together 3115gram / force single servo 1557,5gram

volt at servo 4,2/ volt at receiver 4,90 / force together 3689gram / force single servo 1844,5gram (maximum)

[RudyD54]

I promised someone a while back I’d send some pics of the MiG in my Mini Cooper. Well, may I present MiG-29 and F-22 in the back of a Mini Cooper. 😂
Finally got some decent weather so I’m on the way to meet Hugh Wiedman at the field for the maiden. I’ll report back and let y’all know how it went. 😳👏🏼🤞🏼

[Jacckall]

Telemetry - test 6 Bluebox

Thank you very much for this testing!

[e4dragongunner]

Haha! Jeti for the Win!! Just upgraded to the DS-24. It rocks!! Cool use for a MUI man!

[Evan D]

Interesting how my posts just disappeared... Talking about how James on the pod cast was saying nothing to see here with the MiG and everything is a-okay... I had specific quotes that I heard and put here and now they are gone...

[Borat]

That's a brave thing to do! Unfortunately the weather in the Netherlands is really bad, so no flying for me. But it would indeed be interesting if people could repaet/verify this test.

Word of caution! I don’t want anybody to lose their airplane over this. If you do try to attempt this maneuver, you must start at a high altitude. Once the nose drops, the plane descends very quickly under power with an ineffective elevator control, and you have to perform the following tasks simultaneously to get out of it: throttle back, raise flap and apply up elevator. Otherwise you’ll be in the dirt before you know it. I kept one finger on flap switch as I entered the dive so I could quickly raise the flaps-no flap delay if you have programmed one in.

Let me also reiterate that I always land the Mig with flaps deployed but I’m never above 50% throttle. Once on final I get the plane in high angle of attack attitude and control decent rate with throttle pulses. So again I have full elevator authority at lower speeds and flaps deployed.

[Bushong572]

Mig-29, canopy opening modification.
It took me a week on how to make this work .
No 3D parts, no help, lots of cardboard and balsa and glue, and just old fashion gray matter and lots of coffee and sleep.

Awesome job...........

[janmb]

Interesting how my posts just disappeared... Talking about how James on the pod cast was saying nothing to see here with the MiG and everything is a-okay... I had specific quotes that I heard and put here and now they are gone...

Unless your post contained something really offensive, I don't see any reason why they would moderate something that was discussed on live show just hours ago. Must be a mistake.

Repost it imo.

[Firebird]

Haha! Jeti for the Win!! Just upgraded to the DS-24. It rocks!! Cool use for a MUI man!

outstanding remote - i need one too 👍🏻

[HK111]

Mig-29, canopy opening modification.

Very smooth operation, cool!