I'm building a concept frame from my first sponsor and I'm trying to decide on which size motors to use...

3.5" fpv octo quad... made to carry a full sized gopro and up to 1000mah 6s ..

I'm thinking either 1408s, 1606s, 1804.5s, or 2004s.

Given there are eight, do I need larger wider motors or could I get away with 1408s or should I go larger ???

There’s one octocopter Ive seen that was fairly impressive and used 3” props.
There’s several more pilots that have built it and there was someone offering a frame but it’s been a while.
I like 1504.5 3950kv on 4S for 3.5” under 250 grams.4S 850 95C xt30 tatuu packs give me 6-8 minutes of freestyle ripping.
There’s also 1604 Tmotor,1804 Tmotor,XNova,rcinpower,that are lighter than most and can handle 6S.



 You might use it for a guide or reference and see how it performs on the videos.
 https://youtu.be/RFct7MKpob0?si=Qzjb4UzAwrNR3hb-

(23-Oct-2023, 02:32 AM)Rob3ddd Wrote: There’s one octocopter Ive seen that was fairly impressive and used 3” props.
There’s several more pilots that have built it and there was someone offering a frame but it’s been a while.
I like 1504.5 3950kv on 4S for 3.5” under 250 grams.4S 850 95C xt30 tatuu packs give me 6-8 minutes of freestyle ripping.
There’s also 1604 Tmotor,1804 Tmotor,XNova,rcinpower,that are lighter than most and can handle 6S.



 You might use it for a guide or reference and see how it performs on the videos.
 https://youtu.be/RFct7MKpob0?si=Qzjb4UzAwrNR3hb-

I appreciate it.... seems like I'm in uncharted territory lol

If you are going for 3.5" you would need to consider the very limited prop selection especially for powerful motors. Most 3.5" props are t-mount, only Gemfan has the hybrid mount props, but those hubs are not great for durability in crashes. You would likely get limited return for going with larger motors, but end up paying the penalty for extra weight and current draw. Unless you are planning to run the D90 5-blade ducted prop, maybe something in the 1505ish size range is enough and still give a good balance of power, weight, efficiency? But if you are going to run 6S, you will need to find a motor with low enough kv or end up using motor limits.
If you want to use 6S and more powerful motors, you would probably have better options going for 4", better prop selection, more durable M5 shaft, and more motors with suitable kv.

it will be used as slowflyer for small gaps and stable footage with nice focuses; i would go with smaller motors for efficiency and lower noise. 1306/1404/1505

the only benefit i see for huge motors like1408 is carrying more weight - for the cost of much much more noise and less efficiency. it depends alot on the framedesign, the weight, what motorcombination matches well.
i beleive it would be much better if you dont need to go for the 1408 size

what does the build aim exactly about footage?
what weight might the frame have?

(24-Oct-2023, 08:09 PM)hugnosed_bat Wrote: it will be used as slowflyer for small gaps and stable footage with nice focuses; i would go with smaller motors for efficiency and lower noise. 1306/1404/1505

the only benefit i see for huge motors like1408 is carrying more weight - for the cost of much much more noise and less efficiency. it depends alot on the framedesign, the weight, what motorcombination matches well.
i beleive it would be much better if you dont need to go for the 1408 size

what does the build aim exactly about footage?
what weight might the frame have?

The frame is a concept frame sent to me by my first sponsor in aims to replace several other drones on the market. The few fully built preproduction models I saw were as Powerful as five inch drones, but small enough to fly through very tiny gaps like micros, but could easily carry larger batteries and full sized action cams.

Of course, I'm not a big enough name to get a fully built model, but they sent me 2 frames with all prints as they have customarily done..

(24-Oct-2023, 04:43 AM)mstc Wrote: If you are going for 3.5" you would need to consider the very limited prop selection especially for powerful motors. Most 3.5" props are t-mount, only Gemfan has the hybrid mount props, but those hubs are not great for durability in crashes. You would likely get limited return for going with larger motors, but end up paying the penalty for extra weight and current draw. Unless you are planning to run the D90 5-blade ducted prop, maybe something in the 1505ish size range is enough and still give a good balance of power, weight, efficiency? But if you are going to run 6S, you will need to find a motor with low enough kv or end up using motor limits.
If you want to use 6S and more powerful motors, you would probably have better options going for 4", better prop selection, more durable M5 shaft, and more motors with suitable kv.

I so like my bh 1504.5 motors on 6s. Maybe I'll try running 8 of them and see how that works out. I just worry 8 is barely enough to comfortably carry a gopro

the bh1504.5 might give about 600g max thrust - about 4.4kg thrust.

a 1408 might give over 800g max thrust, 6.4kg in total.
it sounds like a heavy frame about 150g with prints, a gopro170g and a huge 1000mah 6s battery about 180g....
maybe 1408 does match better to climb a good power to weight ratio

Octo is usually bad idea. Lots of propwash. Less efficient than hex.

3.5" - need about 9-15g motor... 1404, 1504, 1505, 1604

obviously, prop size is only part of equation.

1404 is ok for light 4" biblade. 1404 is ok for light 3.5" triblade. But not a heavy 6 blade 3.5" cine prop.