ZBROY Prometheus Titanium Frame 5"

By Jayembee67 on Mar 28, 2021

14  508  8

Another frame-swap build, something that is happening more often of late. But I saw this ZBROY frame a while ago, and whilst it was very spendy, I didn't seem to be able to talk myself out of getting it - I mean, look at it! And this might be the last of the 5" builds too, given all the up-coming restrictions, so why not go out in style then...?

When the ZBROY Prometheus Titanium Alloy arrived, after marvelling at how gorgeous it was for a while, I took all the hardware out of the GEPRC Mark4HD build, and stuffed it into the new frame - it was a bit tight, and finding a place for the capacitor was a rather a game, but it all fitted in the end and looked really nice. Really, really nice. So I took it outside to test hover, and the thing made the weirdest noise and after 20s the motors actually started to smoke very slightly. I have never had motors come down so hot after such a short hover test. I tried all sorts of things; soft-mounting the motors, not-soft-mounting the motors, making sure nothing was rubbing against the FC, swapping out all the electronics in case I had a bad gyro... And every time it took off, beyond a certain throttle, it would start to resonanate, and the motors would get almost too hot to touch within seconds - you could see the frame blurring with the vibration. I really had no idea and feared I would have to abandon this beautiful machine...

But I dug into the BlackBox logs and that was where I discovered my solution. Looking at the traces, holy cow, above a certain throttle the gyros were going bonkers, which the PIDs were fighting like mad, which in turn was strobing the motors to an insane degree. I really have never seen anything like this before. Then I thought to look at the frequency spectrum, and there, like an out of place mountain in the middle of the tundra, was this huge spike of noise at 102Hz - which I can only assume is some sort of resonant frequency of the frame with the hardware I have attached.

I'm not much good at this sort of thing, but I did a tiny bit of reading and decided to drop a 20Hz-wide Static Notch Filter onto this spike and see what happened. And what happened was the machine suddenly flew, and flew really nicely! Crazy how much filtering out that noise spike changed things, but it really just goes to show how important the filtering in BetaFlight can be.

The following Maiden-ish flight was captured using the new Insta360 GO 2 camera, and rendered using the FPV stabilisation. I am still fiddling with the camera settings, there is a bit too much contrast and the colours are a little hectic, but I very much like how the video is looking and I have to say, Insta360 have done a great job with taking the customer complaints about the original GO and truly improving the hardware for the second release.

Maiden Flight

Overall I am now very pleased I effected this side-grade, although I did fear I had made a horrible mistake there for a bit! The frame is a little heavy, but it is so stylish and interesting, I'll overlook that little issue. There is no reason your flying robots can't be things of beauty too!

2021-03-31 Evolution to Final Form
I had to go back in and make some small changes, so whilst I was doing that, I reprinted all the TPU parts, giving them both an improved design, and and overall more appealing colour scheme. This is complete, I would say. Now all I have to do is tune it properly...

Photos

Discussion

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907fpv   Apr 28, 2021  

hey thanks man i messed with the notch filters in the kiss gui and its flying now thanks man your a drone saver!

Jayembee67   Apr 28, 2021 

Fantastic! I've done something vaguely useful today. I should go back to bed whilst I am still ahead... ;-)

But great, I'm glad that worked!

907fpv   Apr 28, 2021  
1

ok i just put all kiss hardware in it tonight so if it dont fly good tomorrow ill try what you were talking about. you know i did turn antigravity off and it did fly better but it still wasnt an enjoyable experience. thanks for the input i appriciate it

Mr. MacGiggles   Apr 17, 2021  

nice build. Are the stl's available on Thingiverse?

Jayembee67   Apr 27, 2021 

Sorry, I got distracted. But yes, they are now available here: https://www.thingiverse.com/thing:4842162

907fpv   Apr 27, 2021  

hey im having the same problem with mine no matter what electronics i put in it. where did you put the notch filter at and where did you get the notch filter? any help would be great because ive pretty much wrote this frame as a lose

Jayembee67   Apr 27, 2021 

You know, I think that resonance is an inherent problem with this frame - I've now talked with 4 folks all who are having similar issues. That's not a good sign - it may be lovely to look at, but I fear it may be style over substance...

Anyhow, I did manage to get mine into the air by applying a software notch filter in BetaFlight. If you look at the last image in the Photos section, you'll see my BlackBox log showing the frequency spectrum, and you can clearly see a spike at 102Hz, which will be specific to my build - you will need to look at your own BlackBox logs to see where you are getting spikes. Once you know where the resonance spike is, you can try to get rid of it with a manual filter.

The one you need is the Gyro Notch Filter on the filters tab in BetaFlight - I set Filter 1 Centre Frequency to 102Hz, and the Filter 1 Cutoff to 90Hz. This creates a filter that removes noise in the range for 90-114Hz, centred around 102Hz. If you have multiple spikes, you can also try using Filter 2, of course. And it did work for me, it stopped that resonance getting into the gyro and making everything go crazy, and the machine suddenly could fly. So it is worth a go... Let me know if this helps!

upioneer   Apr 02, 2021  
1

dig the color scheme!

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