QUAD 750 monoblock

[Jdmagoo]

[Jdmagoo]

[teramax]

[SuperSharpShooter]

That looks like a very tidy build teramax. Which props are you running with those motors? I'm looking for a minimal frame to go with the 5010 360kv motors and 15x5.5 RCT props on 4s. I'm hoping to have a canon s110 on the lightest gimbal I can manage, to use as a long endurance surveying copter.

[teramax]

i also use the RCT 15x5.5 props

[afernan]

@Marcus: What a nice build!. Congratulations, I´m really happy to see that all parts fits so good for you.

I see that you´re using the RcTimer 4215 460Kv. I´ve used that also and they´re even better than 5010. Very well equilibrated and with a nice smooth sound. But wrt endurance, in my experience 5010 are the champions (I get 25min with 5000, 4S). So it´s good to compare performances.

Angel

[afernan]

The crash was not on a 3DPrinted copter. Was a classical aluframe (the small one I´ve brought to Hanover last year).

It was using DIMU. Unfortnally no logs. I´m still having problems with DIMU, not reliable (for me). Some times it "loose" the refference and start this divergence (the crash was after 1h of perfect flight!). This happens mainly when first time PosHold is set. Except for the crashes , all the rest it flies incredibelly well, mainly in heigth control.

The copter was fully destroyed: all four arms bent (this is the main drawback of alu tubes). So I´m rebuilding a new small quad.

[afernan]

@Srinath:
about frequency coupling analysis of the big quad "monoblock", this is what I finally have with the baseline design (arms 315mm), and considering the right Young Modulus for the tube calculated by test:
- arm frequency with 5010 motors: 50Hz
- motor excitation to lift 1666g (hovering) 2273rpm = 38 Hz.

So, not the ideal gap, but enough: not problem now with vibration couplings arm-motor. With 18mm tubes we obtain 60Hz for the arms, that is better, but it´s not mandatory.

The problem was due to the coupling between leg-motor (legs lack of stiffness). With new legs the issue is fixed. I can redesign "T" shape legs with higher stiffness to avoid couplings but with a bit more weigth.

Angel

[Kisssys]

Angel

Looking at your numbers, if you add any more weight and add 250 to 300 grams for a Gopro and gimbal you'll be looking at 50hz motor rpm.

Could you show the math of how you calculate the boom resonate frequency with the landing gear attached to the boom.

[srinath]

Maybe a notch filter on the accelerometer could cut out resonant frequencies that could occur due to loading?
This could turn out to be a generic solution for structural vibrations affecting FC and gimbal performance. I have the C code to implement such filters.
Imagine if the user just uploaded the resonant frequency as a parameter into AQ or gimbal code and the effect of vibration on the video output would go away?