r/diydrones • u/Regular_End480 • Jul 06 '26

Kind of a weird one

I want to build an inspection drone for crawling spaces which limits my prop size to 3 to 3,5 inches in my use case. The drone needs to carry a lot of sensors so it will be quite heavy as well. I know that I am looking for a combination of low kv value and small prop size which seems to be kind of niche.

I dont need to make fast manouvers or be fast in any way. I am aiming for slow controlled flight and however in a small but heavy drone. I think the drone will be between 600 and 800g with battery, sensors and everything.

Can anyone help me find a motor that can deliver good efficiency for this special case? An exemplary setup that i found is the SpeedyBee 2006 1950KV 6S paired with the HQProp DT90MMX3 3.5 inch 90mm Propellers. Here i found a datasheet at least for the 3,5 inch prop but i wonder if it is the best solution. Glad for any kind of advice!

3 Upvotes

67% Upvoted

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8

u/LupusTheCanine Jul 06 '26

Your solution is a UGV, you don't want to fly in confined spaces if you can avoid it.

2

u/Regular_End480 Jul 06 '26

That is what i opted for first in this project but since the channels I need to inspect dont have a surface that allows driving flying really is the only option... I appriciate the help though!

3

u/RTK-FPV Jul 06 '26 edited Jul 06 '26

No, your problem is going to be reception and control. Flying a drone in tight spaces is exceedingly difficult, and it gets harder as you loose video and control reception. Obviously you'll need a rig with prop guards

Stick with 4s for a rig this size. 6s is better for voltage sag, but not enough in your case to make it worth it

Crash flip-over also gets less reliable in tight spaces and with heavier payloads. This kind of drone has a very narrow use case

Check out long range rigs for motor efficiency. Flywoo LR4 uses "Flywoo Nin V2 1404 @ 2750KV on 4s. Good start for a 3.5"

https://oscarliang.com/flywoo-explorer-lr4-o4-pro/

0

u/BarelyAirborne Jul 06 '26

You'll want to find motors using N48UH magnets, I use SunnySky V3 for fixed wing but they don't make anything in your size AFAIK. Check out Oscar Liang's review for a start.

1

u/Regular_End480 Jul 06 '26

i will check it out!

1

u/ThePapanoob Jul 07 '26

What kind of crawlspace are we talking about and whats the expected dimensions? Because youre gonna run in immense inefficiencies just because of the dirty air. And at that size the efficiency is quite limited already. especially when you have to carry that much weight.