Max performance sub 250g quad (4")

By Mahagoni on Jan 13, 2019

4  1,364  11

This is a 4" build whith an UAW of just 248g including a 850mAh 4S battery. To archieve this one has to start with the proper frame. The Druckbaer Ultralight 3 in the 4" version weights just less than 30g. The HGLRC F440 stack fits in perfectly. I choose the 40A version because the smaller ones do not support Blheli 32. Motors are EGODRIFT Shadow 1407+ 3800KV ( Before I burnt through some Kingkong XT1406 1406 3600KV and AMAXinno 1306 - 3100KV motors on this quad. A buzzer is mandatory for me. I wanted three balde props and choose Dalprop T4040. In order to keep the weight under 250g nylon nuts were used for the propellers and the XT60 connector cabe must not be to long. Only three screws per motor are installed. I believe this is the most powerful quad currently possible under 250g with >800mAh 4S batteries. (With 650mAh 4S batteries a 5" Druckbaer Ultralight could be build, but then I think one runs into problems with the amp draw and the flight time might be very short). I had no chance to fly it in the current configuration yet, but with AMAXinno 1306 - 3100KV motors (two of them burnt through on the second pack) I got a flight time of over 8 minutes and it flew nicely. I will report back.


Part List


Druckbaer Ultralight 3 - 4 INCH

Flight Controller

HGLRC F4.V2 Flight Controller for XJB F413 F428 F438 F440 (22 builds)


HGLRC DinoShot 40AMP 3-4S BLHeli32 4in1 ESC DSHOT1200 for XJB F440


DALProp Tri-blade T4040
See Site

FPV Camera

RunCam Micro Swift 3 V2 (9 builds)

FPV Transmitter

HGLRC XJB TX20-V2 Mini 5.8G 48CH Raceband VTX (5 builds)


TBS Crossfire Nano Rx - FPV LONG RANGE DRONE RECEIVER (1491 builds)

Misc Parts

M5 Nylon Nut (10pcs/bag)
Show stores (6)


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DrDeeZee   Apr 08, 2019  

Nice looking build! I am looking to build a 3 or 4" turtle/split carrier, with the main focus on efficiency / flight time for midrange cruising.

fovea   Jan 14, 2019  

the hq4045 should be nice. for max try the hobbywing 1408 2400kv with 6s:
i like your build, love 4inch..

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jcnz56   Jan 17, 2019 

hq4045 are actually "lighter" props. they are the most efficient 4 inch 3 blade i've seen. another choice would be dal tj4045. I wouldnt be brave enough to run your current props on my 1407 3600kvfor fear of burning my motors. Your current are bullnose which increase power use and heat much more than the extra pitch of the ones ive metioned.

Mahagoni   Jan 17, 2019 

Hmm. Did some hover test: DAL T4040: 13:48, HQ4043: 14:06 (+2%)
Given the uncertanties this seems to be not to much of a difference although under dynamic load the HQ might do even better as they are lighter. Subjectively I think the motors get warmer with the HQ4043 (IIRC that's why I did not mount them in the first place - the lower weight is OTOH a plus - but may be also the reason for the longer hover time)

fovea   Jan 18, 2019 

painfull testing - spending 30minutes for it, intressting. thanks for posting results. while changing motorspeed at realflying this should be diffrent. i like the hq4x43 because of response and linear acceleration. give them a try, it would be nice to hear testing results or flight footage.

fovea   Jan 14, 2019  

he wrote he get over 5min flytime in the video description - also really nice, but 8minutes flytime is awsome... i now the hq4x43 as one of the best efficincy prop, you shuld get even more fly time with it. but at so much rpm this could be temp issue with the flytime, if the ampdraw is low enough a 650mah could give some extra power and cooldown.
if you could post a dvr, would be very nice. im sceptical about your bullnose props, never try them, would be nice to see how they perform on your build.
thanks for posting your build and reply

fovea   Jan 14, 2019  

with nylon nuts and an xt30 on 550mah6s it will be under 250, bloodylordv s build come with 254g.

sry i wrote wrong - the hq4043
would be healty for motor temp and efficiency...

Mahagoni   Jan 14, 2019 

I will consider the props after I did some more testing. Thanks.
This build would not do on 6S anyway as the stack is only 4S as well.
4x Nylon nuts are -1.2g. BloodyLordV ( could probably go under/at 250g: A shorter power cable and undrilling and shortening of the motor wires could bring him there.
For the frame and the stack I cannot find weight data but I assume the Airbot ESC is heavier than this one here. Once a weight for the DemonRC legit 4x lite frame is published I could compare it.
The motors are + 7.2g, XT30-XT60 is -2.4g. I could save another 2 grams with a runcam sparrow and a TBS unify nano. Battery (6S 550mAh - 4S 850mAh) is about -3g. If it turns out feasible I might look into a 6S build although I find the 3:30 minutes flight time a bit short.

fovea   Jan 14, 2019  

where can i find these nylon nuts?

Mahagoni   Jan 14, 2019 

Just google for "M5 polyamide nuts". I found this example (the store I got them originally from does not seem to have them anymore):

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