Sub 250g 5 inch
By Cheredanine on Aug 03, 2017
So faced with more impending drone restrictions in the UK I thought I would try building a sub 250g 5 inch quad.
The frame is not a full stick but 4x 4 inch arms (not a typo, the 4 inch arms allow 5 inch props in this config) and three of the small plates, I tried various standoffs, the pictures show 20mm but in the end have gone for 15mm. I could have saved some weight by using the kisscc fc but wanted tie asguard for current monitoring. The power system uses an xt30 (had to shorten lipo leads and change the connector. I have a set of rotorgeeks 1407 2800kv to test with also, will be trying various lipos in the 650-850 mah 3s and 4s to get the best flight times and performance
(Photo on the scales is auw with tattu 650mah 4s at 219g)
Edit: blew the fc (human error), replaced and fitted with 2800kv, second photo showing with optipower 850mah 4s (shortened leads and xt60 replaced with xt30)
Video below shows full flight with 850mah 4s, gf 5030 and rotorgeeks 1407 2800kv
About 6 mins flight time flying like that, top end not up with fastest racers, but not bad
Tried racekraft 5038, less efficient, didn't notice flight characteristic improvement, (about 1 min less flight time)
Then tried 650 mah (still with the racekraft, lost another minute flight time and pretty bad voltage sag, will try 650mah with 5030 next.
Switched to 3200kv, flight time with 5030 - 5 minutes, more speed, certainly plenty for acro, although wouldn't match top end 5 inch racer, cornering though is very quick (less inertia I suppose), in theory I could go higher kv and sell a bit more flight time for more speed, however voltage sag is pretty steep already, don't think 850mah would cope well with higher kv, this seems to be the sweet spot
I must say a big thanks to EngineerX for his motor tests data and extended conversions on motor choice
Note current monitoring not set up
Stock pids and filters
And with 3200kv, I am not a serious racer, but pushing the speed, still haven't bothered tuning, motor 4 has developed some vertical play after crashes, but this gives an indication of speeds, it can do faster, trick it to master its tendency to gain altitude
4 mins 30+ flight with juice still in lipo on landing (I know it's not Charpu, trying to give evidence of capability of quad, not the pilot :)
Tried hq5045 however two issues- firstly weight, even with my lightest 850mah it was 251g, secondly although the motors can handle the props, the lipos can't handle the amp draw, anything in the top part of the throttle produces lipo warning even on take off with a full lipo.
Then tried a set of carbon hq5045 and they were much better, lipo can just about handle, need to shave a gram off the weight and replace a motor that dies today in a crash. Below is a (short) video demonstrating speed using 5045 on 2800kv, flight time flying like that is about 3 mins 30
Hq5040 carbon/nylon:
SUMMARY:
Using 850mah 4s on 5 inch using rotorgeeks 1407 (other manufacturers may give slightly different results, testing done with carbon-nylon or glass-nylon, on occasions I used pure nylon performance was worse as was efficiency
For acro:
3200kv or 2800kv with 5030 is excellent with huge flight times
For racing:
2800kv with 5040 is best
Either with 5045 is a close second but has slightly less too end and bit of a plateau on throttle, 3200kv also pushes the lipo somewhat
In either case 3-3.30 flight times
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killer setup! thwse super lightweight setups are my favorite. I have a question for you though. When you switched the xt60 with the xt30 did you experience any issues? Did you feel like it was bottlenecking anything? Ive got a 4 inch setup with an xt60 and 12gauge wire. Im considering switching to an xt30 with 14-16gauge wire. It's currently 130grams dry (with props) and its setup with 1407 4100kv cobra motors and 4 in 1 28amp esc. I'm a little concerned that if i switch to an xt30 and get it stuck in a tree or something that I might melt an xt30 trying to get it out. Im assuming amp draw gets insane when things get stuck. Thats my main concern. On the bench my motors draws 25amps EACH at full throttle. In the air though I know that number would be far lower (15amps give or take) so im kind of on the fence. Any thoughts?
Excellent! thatll drop the weight into the 120's. My 12gauge wire is HEAVY lol. Last couple of questions, what wire gauge would you reccomend? And do you have any experience with the lightened version? The xt30U? It's the same piece but lighter and with less plastic. it's still the same shape and compatable with regular xt30.
you have to remember that AWG ratings are for constant current, we run with varriable current for a very short time, the AWG ratings done match our usage. i use 16AWG pretty much on all my 4 inch and below, but that is because of cinvenience (lots of 16 AWG with silicon sheathing to hand). i have used at least one of the xt30u on a quad, i dont believe it makes any noticable differemce, but it is of course subjective.
This is very interesting. Would like to know max flight time when available (and the type of flight you did). Is it for slow flying or racing?
The blown fc and motor held me up for a bit but intending to get flight times using both sets of motors for 650 and 850mah lipos, 3 and 4s, and where possible try a few different props. I will add details here together with flight times as well as some dvr footage so you can see the flying style for the flight time (then you are not at the mercy of how good I think I am in my own head :))
I'm not sure if pirofliprc ships internationally, but they have 1407 2700kv. I think it would be perfect for this build
Pyroflip ship internationally, however their motors are brother hobby rebrands, whilst they are excellent motors, they are 1.5g more weight each (and I believe that is without the lock nut so more like 2g) than rotorgeeks, which means an extra 8g overall. With an optipower 4s 850mah 50-100c (97g) this weighs 248g, putting the pyroflip motors on would push it over the 250g limit (the odd gram here and there is a killer)
This is very interesting, I didn't think a 5" quad was possible under 250g. My 5S batteries are 170g so . . yeah, this is cool. I live in the USA and a recent lawsuit (Taylor vs FAA) nullified the restrictions for registration for now, but this is good to know. This quad looks a little fragile :) so I am curious how it holds up to flights over time. A video would rock!
Hi mate,
It looks fragile, everyone who has seen photos says that, but the arms are 5mm, they have less flex than many of my normal 5 inch quads, on the whole it is very strong, although crashes will tell :), camera is more exposed than I would like, but largely protected by the arms
Will be testing various different lipos and props, as well as switching to the 2800kv motors at some point for testing, try and find the sweet spot for flight time and performance, will upload some flight footage during testing
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