Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[GliderGuy]

FF5 - I have to ask....We’re you using any add on RF filter ferrite chokes as previously discussed on this forum? If so, please describe their placement.

-GG

[GliderGuy]

Duplicate post / my bad

[fishface5]

FF5 - I have to ask....We’re you using any add on RF filter ferrite chokes as previously discussed in this forum? If so, please describe their placement.

-GG

No I was not

[GliderGuy]

Would you mind detailing your radio setup? Thanks again.

-GG

[kallend]

Congrats on the maiden Jan!



My guess is the servos are being constantly overloaded as Kallend suggests and when certain conditions occur/converge on the whole power distribution system, further taxing available voltage/current, then that is too much for the servos and they give up, being unable to deliver the required torque to keep servos 'trimming the jet'. Thus the airflow deflects the tailerons to the point where they exert no moment on the hinge and that sends the jet diving. So the amount of the jet diving is exactly the required trim, so to speak, which went missing when servos overloaded. That would also explain why the jets don't just keep flying straight but rather dive. The nose-heavier the jet, the worse it will dive in such conditions.
speeds from available videos ;)

. . . . .

Originally posted by Firebird View Post
Assuming the mig needs about 100gram downforce at each elevator tip for straight and level cruise, the servo might be close to stall after continuous stress. At around 5:50minutes the servos didn’t correctly follow their commands anymore until they fully stopped to follow at around 8minutes. The measured temperature at the servo rised from 21,7 c at the beginning to 36,2 c (f) at the end of the test.

Outstanding work, very well done!

. . . . .

.

No need to assume the downforce at an arbitrary location. Quite easy to make a very good estimate of it as a function of CG location from the data already available, and the position of the CP of the FFS has already been posted.

[RC30Flyer]

Was just thinking, is there any way to static test the elevators with some weight that would correlate to simulate in flight load? One would have to figure out an approximate amount of weight that would simulate cruising speed airflow and then also weight for full throttle speed. I'm thinking this would save some jets because the failure would occur on the ground in a controlled way. You could even run the throttle to simulate voltage drop like it was happening during an actual flight. Any thoughts?

[fredmdbud]

Was just thinking, is there any way to static test the elevators with some weight that would correlate to simulate in flight load? One would have to figure out an approximate amount of weight that would simulate cruising speed airflow and then also weight for full throttle speed. I'm thinking this would save some jets because the failure would occur on the ground in a controlled way. You could even run the throttle to simulate voltage drop like it was happening during an actual flight. Any thoughts?

In addition to gravity, tail drag adds to the load on the elevator servos.

The attached figure assumes the tail's CP is at the tail axle - but that is not the case, so its lift force is yet another additional load.

[Edwin-0]

Did my maiden yesterday. Battery 5800ma gens ace 45c. Only 3 clics right to fly straight.
Reinforced steering rods and upgrade servo's. Nice flying image and nice reactions in the club.
Must say that with 35c batteries and the missiles installed I need a serious longer track to get off the ground.

https://www.facebook.com/groups/motionrcfanmedia/permalink/833914544090128/

[Bushong572]

Can anybody tell me the diameter of the wheels on this jet?. I want to add brakes to it.

I recently changed my front wheels and added brakes to the mains. I went smaller (sorry, I don't have the stock wheels anymore). I believe the stock size was 65 front/ 81 mains. I went with JP 45mm fronts and JP 65mm mains with brakes. I would not go any bigger on the mains because of weight. The plane looks much better. I'll try to post some pics later today.

[GliderGuy]

Did my maiden yesterday. Battery 5800ma gens ace 45c. Only 3 clics right to fly straight.
Reinforced steering rods and upgrade servo's. Nice flying image and nice reactions in the club.
Must say that with 35c batteries and the missiles installed I need a serious longer track to get off the ground.
https://www.facebook.com/groups/moti...3914544090128/

Nice landing and congrats!

Would you mind listing the details of your set-up. Please include EVERYTHING including receiver type and your radio installation details? We need to analyze the successes as well as the nots. Thanks!

-GG

[GliderGuy]

Was just thinking, is there any way to static test the elevators with some weight that would correlate to simulate in flight load? One would have to figure out an approximate amount of weight that would simulate cruising speed airflow and then also weight for full throttle speed. I'm thinking this would save some jets because the failure would occur on the ground in a controlled way. You could even run the throttle to simulate voltage drop like it was happening during an actual flight. Any thoughts?

Good thinking. Look back at all the testing Firebird has done (prior posts). We await actual flight load telemetry when he gets to fly his MiG.

-GG

[kallend]

In addition to gravity, tail drag adds to the load on the elevator servos.

The attached figure assumes the tail's CP is at the tail axle - but that is not the case, so its lift force is yet another additional load.

No need to assume anything. The CP is already known and it's way behind the axle.

[PieterO]

I know that most of you have something else on your mind, regarding all these crashes (I've read every single post on these 139 pages) but I still would like to share these nice pics a fellow pilot made of my Mig:

[Edwin-0]

Nice landing and congrats!

Would you mind listing the details of your set-up. Please include EVERYTHING including receiver type and your radio installation details? We need to analyze the successes as well as the nots. Thanks!

-GG

I had two flights yesterday.
Flight 1 - battery 5800ma (+/- 880gr). CG spot on the marking on the wing.
The first test with batteries 45C and no racks I forgot to put the flaps on the takeoff, but no problem.
I have been flying with Spectrum for years and the receiver and satellite is at the front of the nose.
The servo's were replaced with the included upgrade, but I also replaced the steering rods and connections with 3mm rods.
The elevators are both on a different channel directly in the receiver. All the rest goes through the blue box.
Here the wheel doors have been moved to the double function.

What I did change is that both ailerons and flaps are set in such a way that they both end up in neutral position just above the wing. This was something that was in one of the previous posts and according to this would prevent the nose from sinking into high speed low pass.

did not have anny issue with all of that.

Flight 2 was one with the rockets on the aircraft and 35c batteries and on our grass terrain I had to give a hard pull to the elevator to get off the ground.
Maybe this was just because of the higher C content of the battery, this will have to be tested further.
maybe with these settings i use, of ailerons/flaps up above the wing and elevator setting (see pictures), I could give it another trim click down, the plane has something of a tendency to lift the nose in full speed now bud it is ok to fly.
Too bad but yesterday time went too fast here in Belgium.

[Evan D]

Now 11 have answered the crash poll. 10 with upgraded FW servos and 1 with the original pre updated FW servos. 9 stock BEC and two non stock.

[janmb]

I know that most of you have something else on your mind, regarding all these crashes (I've read every single post on these 139 pages) but I still would like to share these nice pics a fellow pilot made of my Mig:

Thanks Pieter, we need some of that good stuff too :D

In all of this investigation going on, it is important to not forget how gorgeous this model really is.

[fishface5]

Would you mind detailing your radio setup? Thanks again.

-GG

radio is a IX20 was using a admiral gyro receiver. Now these receivers have been good i have them in other jets with no issues

[awat70]

I recently changed my front wheels and added brakes to the mains. I went smaller (sorry, I don't have the stock wheels anymore). I believe the stock size was 65 front/ 81 mains. I went with JP 45mm fronts and JP 65mm mains with brakes. I would not go any bigger on the mains because of weight. The plane looks much better. I'll try to post some pics later today.

Thanks for the information.

[Jet jocky]

Do you think maybe if possible to disassemble the servo and drill some holes on both sides of the case to give the heat some place to go?

[GliderGuy]

Do you think maybe if possible to disassemble the servo and drill some holes on both sides of the case to give the heat some place to go?

Whoa - We must keep in mind that all the great testing done by Firebird was without any airflow and with static loads which may or may not represent actual flight loads...and up to 6 min, the servos were doing their jobs. We don’t fly the MiG for 6 minutes usually.

Before too much more brain power is brought to bear, we should be patient and wait for Firebird to report the telemetry data from actual flights.

Once we have REAL data, then.......

-GG