Moved: Reply To: Modified Mini tri canopy?

[Terje]

That issue is more than outweigh by the mass of the motor not shifting as much side to side. The tail mechanism is mounted higher, yes, but the actual motor is at the same height or even lower, depending on which motor is used.

[Kevin_Erik]

Yeah but if you can manage both then there would be ZERO tailwag.

[Terje]

When using the impossible tilt, the tail tune is unable to succeed because the acc is unable to pick up the movement of the motor… So pretty close to perfect 🙂

[Kevin_Erik]

Can a 2207 sized motor fit ?

https://farm1.staticflickr.com/820/40641431435_8a7e561c06_z.jpg

[Terje]

I made the low profile version for the Emax MT2208II (lovely motors btw), the 2207 you link to, are 3mm lower. To be honest, I don’t know.

[MadPoet]

How did I miss this “impossible tilt” when searching thingiverse, crazy. Of late I have been playing around with PETG and I have some TPU on the shelf to mess with later. What material would be best for this, ABS, PLA, PETG, TPU? For quad parts I like the flex I get from PETG but it seems to shatter easier than ABS or PLA. Thank!

[Terje]

The relative elasticity of ABS/ASA makes it a good candidate. Scale 101% or what ever shrinkage you experience. PETG works too, but in any case you should print spare motor mounts, since they tend to break on hard impact (not a perfect solution)

[jihlein]

I think there’s a lot of misconceptions going on about what the tailtune does, and doesn’t do, and what’s causing the tailwag.

1)The static tailtune only configures the servo setpoint positions (left/center/right), and the servo speed. There’s a bit of a catch 22 here, as the servo speed needs the fdbk wire to be computed, yet the servo speed is only used in the virtual servo model when there is no fdbk wire. In fact, if you manually set the servo setpoints, there is no need to run the static tailtune. I’ve proven this with triflight running on dRonin firmware as it is setup somewhat differently. You also can see this by examining the code.
2)The dynamic tailtune is only used to set the motor thrust factor, and the only thing measured here is servo trim position in hover trim. To be in hover trim, you need to be off the sticks (inside a deadband), and also have the yaw rate within a certain deadband. The accelerometers don’t come into play here. If the dynamic tailtune does not complete, it’s because the prerequisite conditions for hver trim have not been met. Dynamic tailtune is NOT a substitute for proper yaw PID tuning.
3)The tailwag, in my opinion, is primarily due to a yaw loop gain that is too high. I won’t go into the gory details of the code, but there are calculations to increase the yaw force at low throttle settings, and I believe they are too aggressive, giving too much yaw gain at low stick settings. A lot of these calculations are relative to mid throttle stick. The situation is worse on the baby tri because it’s so powerful it hovers well below mid stick where the loop gain is increasing. On the latest triflight, there’s no easy way to adjust his that I’ve found. I’m flying a modified version of the 0.5 release where there are independent gain adjustments above and below mid throttle. I adjust my throttle curve such that the copter hovers at mid stick, and tune the yaw pid loop at that point. Then I adjust the dynamic yaw upper value for no tail movement on throttle punches, and the dynamic yaw lower value for no tail movement on throttle cuts. I’m not the most aggressive pilot, but this has worked, and still works, very well for me.
4)The dynamics of the thrust centerline wrt the IMU, while they certainly play a part, is very secondary to getting a proper pid tune, particularly with the small distances we are talking about. I don’t think there’s an issue wrt to the gyro rates at all, and the effects on the accels could be compensated for with some lever arm corrections, but if you look at the math, these corrections are very small. Add the way the most pilot’s fly these (rate mode for acrobatics), the accels don;t come into play anyway. With the modeling I’ve done, I agree with Terje that the rotational mass of the motor being lower is more important than the thrust line being a little higher.

As a side note, I mentioned I fly triflight on the dRonin firmware. dRonin has and autotune mode that works extremely well, but I’ve found one interesting artifact. If I use any D gain what so ever on the yaw rate loop, I get tail shakes. Setting yaw D to zero cures this and the tail responds very well with no shakes.

I’ve done some simulation work on this in Matlab, but it became too much like my day job. Maybe I’ll pick it up again someday….

Whew, it’s too early in the morning for these mental gymnastics…. 🙂

[Kevin_Erik]

@Terje

I opened the low profile version of the Tail-tilt in Fusion-360 and compared it to my 2207 motor mockup.

https://farm1.staticflickr.com/876/41514010892_67b2fdfc9f_c.jpg

From that, i think it should be fine.

Which mount / support do you think will work best for the low-profile version and the TRI_baby?

Note: I tried to open the .STL to edit and could only open this as a mesh.

[Terje]

It is actually the servo that is the limiting factor. You might have to trim the mount plates on the servo to get enough clearance. Regarding servo mount, the original RCE mount should fit just fine. Alternatively cut down the tall mount to fit. I have not tested it against the new steel servo gears. Otherwise it is a trade off whether you want the mount or the servo to fail.

[Kevin_Erik]

Yeah, been trimming the servos as it’s extra weight. Just need to make a support for the motor side opposite of the servo. Wish everything were directly editable as its a real pain if i have to modify something as I have to recreate it from scratch.

As for protection, I’ve never had a moment where the tail-mount took a hit that the servo didn’t also fail.
Besides, anytime the tail-mount would fail would lead to a total loss of control and likely further damage. Should the tail-mount stay together its at least likely that the Copter could land. Either way I’ll lose the servo but at least not have to repair the whole Copter.

[Terje]

Hi Kevin, I’m going to ask you a few simple questions that will help me better understand the problems you are having. I hope you take no offence.

1) Have you installed Fusion360?
2) Have you imported the .F3D file(s)?
3) How old are you?
4) What country do you reside in?
5) What is your level of education?

Cheers

[Terje]

Looks good @jihlein!

Would you mind sharing the file for the rear part of the mount, that is made specific for the babytri?

[jihlein]

@Terje, certainly, see attachment. I should have attached it to the original post….

Attachments:

1. Impossible_tilt_back_baby.zip

[Terje]

Oh, did a quick edit myself. See if you like it 🙂

Attachments:

1. impossible-tilt-back-babytri.stl_.zip

[Author]

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