Last month I found a some nice spots around my city with some steep valleys, a little river running more than 50 meters down and a big deep canyon with beautiful ridges. I tried to fly there but my current 5inch just drain  lots of their batteries in the climb ( I got just a couple of dives before landing), and my Explorer LR 4inch is just too slow and gets push around with the wind.

So, I bought a RDQ SourceOne 7inch frame and started planning my next build:

Frame: RDQ SourceOnce DeadCat 7inch
Stack: Mamba  F405 + F50 esc
VTX: Rush tank Solo / Unify Pro Pro32 HV
Battery: 4s,5s or 6s LiOn (Getting big 6s Lipos here is next to impossible, thanks god for the vape trend)
Camera: RunCam 5 Orange or GoPro Hero 8

Being a newbie in FPV and never even seen a real 7inch, Im lost in which power train to use. I want to get around 10min flights

I understand that I have a kind of heavy setup, but no idea what motor or KV to choose, for what I researched I can have anything from a 24XX to a 28XX. The main contenders so far are:
- Emax Eco II 2807 1300Kv
- BrotherHobby 2507 1500kv 

any recommendations?

I have BH 2507/1500 and happy with them.

A lot of peeps are using a 28xx motor and like them.

Just don't go much below 25xx

(28-Jul-2021, 10:58 PM)Krohsis Wrote: I have BH 2507/1500 and happy with them.

A lot of peeps are using a 28xx motor and like them.

Just don't go much below 25xx

What kind of battery do you use? 5s or 6s? How much flight time?

https://quadmeup.com/how-to-choose-motor...adcopters/

BH 2507 1500KV here also. Run them as 1500kv for 4s and 5s and getting 20min with a 5s 5000mah. 1200kv for 6s.

BH2507 and Racerstar AirA 2508 are the minimum.
And probably best with lighter build and low-pitch.
I use Xing2806.5, but they are 50g heavy and power hungry.

28xx (or bigger) makes a huge difference you can only feel when you go back to underpowered build.
Bigger /heavier prop takes longer to spin up and you get lag. You will still eventually get high speed.

Its like 4 cylinder truck with slush-box automatic. You hit gas to pass, but its slow.
When you are coming out of a mountain dive, dont want to be pulling up way early fearing you wont make it.

These are very good motors.
https://fpvcycle.com/collections/motors/...s-8s-motor

300mm+ trueX frame should even fit 8". Get low-pitch biblade for extra range.
https://www.getfpv.com/master-airscrew-m...black.html

If the frame "cage" is in the way, you can mount stack/etc upsidedown, and battery "ontop"

My advice:
1. Flying 1km+ -> always have GPS, DVR and Failsafe thouroughly tested and running.
2. For big quads (6inch+), always build 6S.
3. Motors pulling under 50A, use XT60 and AWG12 - the biggest wire that fits.
4. 7inch = 1300KV. 8inch = 1100KV. For range you want Masterscrew biblade like link above.
5. Strongly reccommend ExpressLRS. If you get 900Mhz, you can run much longer range video on 2.4Ghz!!
6. Spend $$$ on best antennas you can find. TrueRC. Lumenier Axii.
7. A big expensive quad with expensive camera -> minimum F7 60A ESC stack. You need the UARTs, and peace of mind.
8. ALWAYS get best battery possible. Smallest 7" LIPO I use is 400g Gaoneng 6S 2200Mah 130C.
On my BH2812 9" I use XT90 and 2600mah, 3300mah and 4500mah.

watch this about 9".


Magic formula for keeping props subsonic

For "Long Range" LIPO use 80% of this max KV..but if you are using Li-ion, it cancels out.

60 = PropInch * Cell * maxKV
3", 4S max 5000KV
5", 6S max 2000KV
7", 6S max 1430KV ->
8", 6S max 1250KV ->

I would not take JB's advice for anything other than a 5" quad.

Anything smaller than a 4" or bigger than a 6" or even Long Range: you need to watch a different reviewer's opinion.

The vibration on that 9" Merica is because the HQ MacroQuad Prop 9X5X3R props are not balanced from factory and the advice is to balance them and use the hub adapters that came with the props (something we rarely do on 5" frames). Also the pid/filter tune CMW provided for that quad will get you air but is alot to be desired for : https://textuploader.com/tsvab

(28-Jul-2021, 11:25 PM)PeladoMat Wrote: What kind of battery do you use? 5s or 6s?  How much flight time?

I use 4s 4000Mah battery on it.  With my normal style I get around 18 minutes (cruising @ 45mph).  If I practice good discipline with the throttle (cruising 35mph) I can get around 24-25 minutes.

I agree with Kafie, JB is probably one of the worst to listen to for LR.

another confirmation about that, name it the positive way; jb is knowledgable about 5inch freestyle quads

i use some 2407 on a lightweight 7inch 350g buildweight, im happy on them for efficiency and as a surfer.
personal i would go for the 2807 for efficiency if your buildweight wont be low. i believe on a low buildweight not to heavy battery the 2507 might provide better freestyle ability.

Thanks all for your help! I agree that JB is not the best resource for 7inch, he statted than in more than one video.

Im loosely following Pawel Sites (https://quadmeup.com/ and https://fpv-shopping-list.com/), but he also swings between  the 2507 Avengers and the 2807 in the different builds. So I tried to get some information with e-calc.ch.... only to get more confused:

2806.5 1300KV motors - 6S1P 2600mhA Molicel LiOn - Dalprop Fold F7




2507 1200KV motors - 6S1P 2600mhA Molicel LiOn - Dalprop Fold F7


The flight times seem a little short, and quite close... I am doing something wrong?

the buildweight is 350g and the battery 300g = 650g
the allupweight is named as: 1142g


i dont know, doesnt use ecalc frequently, seems there is something wrong. 500g more give a huge difference in flighttime

(29-Jul-2021, 08:05 PM)hugnosed_bat Wrote: the buildweight is 350g and the battery 300g = 650g
the allupweight is named as: 1142g


i dont know, doesnt use ecalc frequently, seems there is something wrong. 500g more give a huge difference in flighttime

The calculator sums also the weight of 4 esc and the motors, 450g. The 350g are only the frame + fc + vtx + camera. It took me a while to understand how e-calc works with the build weight.
Around 1200g AUW seems ok for the build, al least what I saw in rotorbuilds.com

I can say the BH2810 1500KVA motors work very well. They do however need a very good FC,ESC combo. They toasted my 55A lumenier razor ESC in a few flights. Changed to the Tmotor full size FC and ESC stack and my 7” flies like a dream. It feels like it has wings because of the larger props. Now if I can just find a big lipo in stock for a reasonable price I could truly find how far it can fly. With a 1800 mah 6s I can only fly 4 miles round trip but there is a lot more range available with a bigger battery I’m sure! Just make sure you have a very accurate GPS, I already had to have an emergency landing cause I forgot about battery level. After entering the GPS coordinates from the googles to a GPS app I was able to find exactly where I landed it. Amazing technology.

(29-Jul-2021, 08:24 PM)PeladoMat Wrote: The calculator sums also the weight of 4 esc and the motors, 450g. The 350g are only the frame + fc + vtx + camera. It took me a while to understand how e-calc works with the build weight.
Around 1200g AUW seems ok for the build, al least what I saw in rotorbuilds.com

thats very heavy, seems you will need a 2p 5-6s or lower the weight to achieve longer flighttimes

(29-Jul-2021, 09:33 PM)hugnosed_bat Wrote: thats very heavy, seems you will need a 2p 5-6s or lower the weight to achieve longer flighttimes

Well, I think that i had a :: moment...  you were right 1200g is way too heavy for the build. I double checked all the builds at rotobuild.com and only one is over 1100g All Up Weight (Quad + Battery + go pro) all others are around 900gr. Now all the e-calc seems to match what I read there about flight times.

Now I have to think about the max amp... for LION the total amps is limited... so, a 5S2P config looks better now: