18-Jun-2023, 07:08 AM (This post was last modified: 18-Jun-2023, 07:09 AM by ph2t.)
I was watching kabab's TP3 video again the other day
He talks a lot , but now with further experience in building toothpicks I started to listen to what he was saying, how he was focusing on fundamentals of quad flight and the relationship of weight, to thrust, to prop size. It got me thinking through my own experiences with 3" 1S builds and so on.
I like flying around my house, there is a lot more opportunity to do it than go to the local park and rip the 5" quads. I like what I've been able to achieve with this tp3 build: https://intofpv.com/t-1s-toothpick-walks...ild?page=4 whilst keeping everything quiet so it doesn't disturb the neighbours and is still relatively light weight / low impact.
So if I can get 1S on 3" to perform, can I do 2S on 4"
The darn flying hotdog was 200g, ran on 1204 motors and wobbled to all buggery. But If I could get the weight down maybe I could get something that would handle well and run quiet.
1S on 4" with any performance is impossible. There are just no motors with high enough kV and motor size (think 1204 and larger) to do the job, not that I've found anyway.
2S is doable though, with the motors in the spare parts bin I sorted out:
1104 tmotor, 7500kV - could work, to small.
1207 rcinpower, 5000kV, would work well, but heavy.
1204 rcinpower 5000kV, what I had on the hotdog, could work? should work!
vtx is walksnail 1S lite version with nano camera with truerc antenna
went with the rcinpower 1204 5000kV motors
gemfan hurricanes 4024 props
I got the dry weight to 85g which is not too bad!
I've done a bit of tuning and also investigated the use of the ICM42688P by JHEMCU on this AIO. I decided to add a large low esr capacitor to help with filtering. I'll post more on this later.
For now here is one of the tuning videos with sound. I just wanted to share how quiet it is.
I'll post more on the gyro investigation and also build and tune later, gotta go make dinner now.
18-Jun-2023, 02:31 PM (This post was last modified: 18-Jun-2023, 02:32 PM by ph2t.)
There seems to be a lot of feedback about how poor the ICM42688-P gyro performs. From recurson and momobrut's posts through to feedback on facebook. One day I spotted a post on how someone commented that this gyro is fine as per BF devs statements but FC manufacturers don't design properly for this gyro, resulting in poor performance. This is from a rand on FB and not directly quoted from a BF dev. It got me thinking though.
The JHEMCU AIO in this build uses the ICM42688-P gyro, so I thought I'd investigate it more.
The gyro is mounted up at the front of the AIO, next to the F411 MCU, a couple of RGB leds and the analog camera socket/pads.
From the status command in the CLI, I can see that it is connected via the SPI bus.
For SPI bus this is the manufacturers reccomendation for some bypass capacitors. Note the pin labeled Vdd is where the gyro gets its power from.
The AIO shows this:
The red and green highlights are what I think correspond to the schematic. Whilst I haven't measured these caps it is a good start to see what I believe to be jhemcu at least following the minimum spec from invensense.
This AIO has no blackbox so it is impossible to accurately verify the gyro noise but the flight performance feels good.
I have placed a good quality, low ESR, 1000uF 10V electrolytic cap across the power terminals of the AIO. I didn't test it without, maybe I should of.. the habit is ingrained these days to just add a cap.
The tune is pretty aggresive with filters (both) set to 1.2 for now. I will try some more tuning sessions tomorrow hopefully and once sweet will post the details and some more video.
Very nice. When I read 1204 motors, I thought surely under-powered... but it seems to be flying nicely It will be interesting to see after you are done tuning how it does with prop wash handling and motor stutter. I have a 2S 4" pick, but when I checked the weight, it has grown to around 120g (I think it started out closer to 100g, but it is more a long range li-ion flying).
I don't know about the Ruibet board, I've not been so happy with mine. Not sure if it is the frame, but I am getting terrible shaking at full throttle (more like wave oscillations clearly feel motors ramping up and down) that feels like a bad prop or the board can't supply enough power, but have tried different props and even going down ins size but still the same. At normal throttle range, sometimes it flies smoothly and then other times not... getting ready to swap it out.
19-Jun-2023, 01:17 PM (This post was last modified: 19-Jun-2023, 01:20 PM by hugnosed_bat.)
i did 4inch on 1106 engines and 2s 450-550mah batteries. my bh 1106 had 7100kv. i used the hq biblade.
it flew pretty okish, high average speed, beautifull cruiser mainly.
in my case the motor response was bad, it was about 45-60% throttle which did an effect - throttle was pretty much on-off xD my 1106 hadnt the torq on 2s to spinup or brake a 4inch blade.
average flightspeed on yours looks pretty fast either and it seems consistency. whats the throttle range where the motors does provide enough torq to spin up the 4inch blade propperly on your settup?
Quote:Very nice. When I read 1204 motors, I thought surely under-powered... but it seems to be flying nicely It will be interesting to see after you are done tuning how it does with prop wash handling and motor stutter. I have a 2S 4" pick, but when I checked the weight, it has grown to around 120g (I think it started out closer to 100g, but it is more a long range li-ion flying).
I don't know about the Ruibet board, I've not been so happy with mine. Not sure if it is the frame, but I am getting terrible shaking at full throttle (more like wave oscillations clearly feel motors ramping up and down) that feels like a bad prop or the board can't supply enough power, but have tried different props and even going down ins size but still the same. At normal throttle range, sometimes it flies smoothly and then other times not... getting ready to swap it out.
I think the key thing here is the weight, being quite light seems to help these motors a lot. I've upped the PIDS to the point where they are ready to be dialed back a bit. Getting a bit of prop wash now. As for the Ruibet board I know what you mean. I couldn't get it to fly right on 1S on a 3" toothpick build, I thought extra filtering would help but that didn't make a difference.
Quote:How does it feel in the air compared to a 1s 3”?
It is very floaty, won't drop when you want it to so cornering is trickier. It's also bigger so I'm hitting things more, lol
Quote:That sucker is impressive! How's it handling the punishment of freestyling so far?
Not very well.... I came down hard on the garage roof after hitting a small branch or something and I think big blades on small motors can leverage it to the point of just popping the bell end off! Lost the shaft, weird!
Quote:average flightspeed on yours looks pretty fast either and it seems consistency. whats the throttle range where the motors does provide enough torq to spin up the 4inch blade propperly on your settup?
Before I added some motor scaling (95%) and expo on the throttle, hover was approx 30%, now it's higher but I'm still fine tuning it. I feel like when you start using motor scaling it really drops off the power. I did this to save the battery a bit but I adjusted expo at the same time. Need to fine tune it more as I'm now pushing higher on the throttle stick than my muscle memory likes.
Here's another tune vide whilst I wait for a replacement 1204 in the mail, lol... PIDs need to be backed off a bit and firmware on the vtx needs to be updated, light changes are a bit annoying now.
...to get me in the initial ballpark, say ~4800kv for 4" props. (for 2S)
Do you have something like: 1404/4800kv laying around? I know Flywoo makes a 1404-4850kv fwiw, should work fine, curious how the mass would play out tho? Going from 6g to 9g motor?...
Quote:Couple things for consideration: original TP3 disc area w/3" props= 7.07 new disc area w/4" props= 12.57
Same ~6gm motor used for both? What if you scaled up the motor size/weight/mass proportionally to new disc area size? 1404 close enough?
This is what surprised me with this setup, it was light enough to not be too over-propped and handled well because of it.
I have some 1404 sized motors but the kV is too low, at 2S I still need 6-7000kV to make it pop.
As noted earlier in this thread I have some rcinpower 1207 motors of the same 7000kV as the ones in the first build. I will try them now.
After all my experiments with the 1S rigs I've upped my build quality, comming back to to this build thread the original just looks a bit janky, lol...
, but now with further experience in building toothpicks I started to listen to what he was saying, how he was focusing on fundamentals of quad flight and the relationship of weight, to thrust, to prop size. It got me thinking through my own experiences with 3" 1S builds and so on.
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