So this is an experiment, which I will update as we test.
I have 5" 4S racecars that weigh 400gm in the air for racing. I have 950gm 6" and 7" 4S rigs for long range and filiming and one of them is 4S/5S 6" (1950kv). What I wanted to do with this experiment was build something that could handle high voltage/high RPM with 7" but also be light.
So we are looking at 362gm dry/677gm with 2200mah 5S lipo, which is like the weight of a fat freestyle quad, but with 2200kv/7" 4S (equivalent) drivetrain. Low(ish) weight, stupid high thrust. we'll see how it goes. (FYI these motors are 1750kv)
Update 1: 4S LOS and maiden flights fine, though lacking power as expected. 5S so far has caused the FC to wigout on arming, no successful 5S filghts yet.
Update 2: Betaflight 3.5.7 and dropped pids by 20-30 points from stock, and suddenly it can handle 5S, and it's exactly what I wanted, stupid speed! I only tested it in the dark on a discharged battery, with 45deg cam angle. I'll get it dialed up to 65 (where I race) and charge up lipos and find some daylight and really open it up sooner than later... so we'll expect an update from that as well
Flight Controller |
DALRC F405 30x30 Flight Controller
(22 builds)
Racedayquads.com
|
$31.99 |
ESCs |
Spedix GS35 32Bit 35A 2-4S 30x30 4in1 ESC
(4 builds)
Racedayquads.com
|
$29.99 |
Motors |
4 x BrotherHobby Avenger 2507 V2 Brushless Motor
(5 builds)
Airbladeuav.com
|
$99.96 |
Propellers |
HQProp DP 7X4X3 Propeller (Set of 4 - Light Grey)
(55 builds)
Getfpv.com
|
See Site |
FPV Camera |
RunCam Micro Sparrow 2 Pro
(7 builds)
Shop.runcam.com
|
$41.99 |
FPV Transmitter |
Team BlackSheep TBS UNIFY PRO 5G8 HV (SMA) VTX
(8 builds)
Airbladeuav.com
|
$49.99 |
Antenna |
TrueRC Singularity Long 5.8GHz (SMA) (RHCP)
(9 builds)
Hobbyrc.co.uk
|
See Site |
Receiver |
FrSky XM+ SBUS Mini ReceiverDefault Title
(1149 builds)
Airbladeuav.com
|
$12.99 |
Batteries |
RDQ Series 18.5V 5S 2200mAh 80C Long Range LiPo Battery - XT60
(27 builds)
Racedayquads.com
|
$38.49 |
Try scaling your throttle and adding some TPA @ about the middle and work it down until you get it under control with 5-6S. I run some 2408.5 Hyperlites with these props and it took a good bit of tuning down to get it smoothed out (note: I am talking about BF 3.5.7... My 7" quad absolutely did not like 4). I subsequently built a hex (same Hyperlites, same 7" HQ V1S), and that one flies like an absolute dream (3.5.7 stock tune).
Nice build (also... taking pics on the countertop? A pilot after my own heart!).
oh thanks! Yea I got it working, the issues on 5S were PIDS. they were way too high, and on 4s it was vibrating but on 5S it instantly went apeshit. I dialed pids way the heck down and was able to get some flying in, and it's dope! Check some flight footage here! https://www.instagram.com/p/B4Lx2iZHG_b/
Sticking with 3.5.7 for now.
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I'm kinda glad I'm not the only one pushing this approach - I went for 1550KV on that setup so I'd get a little more flexibility. I think the BF7042 biblades are probably better at carrying speed, because mine doesn't feel terribly underpowered on 5S (equivalent RPM), but is pretty stupid quick on 6S. Surprisingly usable for me on 4S running MultiGP scale and tighter tracks, but that's not what this thing is good at.
3.5.7 has been the answer each time I try something new, but 4.1 with RPM Filtering is probably going to finally top that.
oh for sure I haven't been super keen on all of the new firmwares, I did ge that issue sorted though (dropped P gains like mad)
this one is slightly faster than my current skill level, and slightly faster (I think) than my 5" 4S setup, but I haven't put it on a track yet. I'll probably give it a whirl next race. the 7056 dals have been super good to me, with large enough motors there is no underpowering, and they have incredible speed. HQ props are all to floppy and it honks and oscillates and generally sounds like garbage
Yeah, I was shocked that I was getting a complete honk-fest on cheaper 2507's with those 7x3.5x3's, and it didn't go away on the 7x4x3's.
I've ran this on quite a few tracks - it's surprisingly not bad on tight tracks, the weight just becomes noticeable. Big wide open ones, I still notice not being able to go from slow to fast as quickly, but the top end is there to the point where ShaunT has to run one of his DR.One type quads to keep up with me in a straight line... but I really feel like the performance limiter in those cases.
I do recommend trying the GF7042-2's in clear, it's a different feel and grip level (basically 5" tenacity in turns instead of the loopy high G loads possible on cyclones), but the speed and efficiency are absolutely nutty. The sound is glorious, which is my reason to love them, but flight time, especially cruising, is mind-blowing.