Quad Need help with Custom Quad Build

[Derek]

I have a thought in my head (dangerous words). This is a project that has been inspired by several other sources.

I want to build a custom 500mm FPV quad powered on 6S. My first thoughts were to use 10" props on some 6S 450 class helicopter motors. I was given 4 Align 6S 450 class motors. If I do build the quad with these motors, I'm beginning to become concerned that the quad would be too "floaty." Any thoughts on this?

so....I have these motors, maybe I'll use them, maybe I won't.

Readymaderc.com has some 60amp BLHeli esc's. I was going to order them.

I'd also like some suggestions/recommendations for a new flight controller. I've only ever used the Naze32 rev 5. I've heard some bad things about the rev 6. I don't want CC3D.

I look forward to reading your thoughts/suggestions.

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I imagine I'll have to guess-timate the AUW of the quad. Then search for motor/prop combos that will lift that guess-timated weight (plus 3-4 times that amount), divided by 4.

 

[Stambo]

What is the KV rating on those heli motors, I run 10" props on 1000kv motors on my larger machine, but that is only 4s.
I assume something that big will be mainly for camera work, big slow props means less jello, easier to balance.
As far as a flight controller, I would go with something that is capable of running GPS and auto modes for something that big.

 

[Derek]

1700kv is the rating, Stambo. And no, I have no intent for "mainly camera work." I want this to be a big and fun racer.

So, if you are running 10" props on 1000kv and 4S, for 6S, maybe I should be thinking 7" or 8" props

 

[Tony]

One thing to calculate here is the blades that that motor is spinning now. On a helicopter you are swinging a 31.65" rotor blade. But, you are also running somewhere around a 10:1 gear reduction on a helicopter. In theory you would just divide the rotor head by 10 and get your number, but then you would be at 3.17". Considering this motor is a 6s, has plenty of power and will not have all of that drag that large blades provide, I would think an 8" to 10" prop would be perfectly fine. Also remember, helicopters are running up to 12º of pitch and more than likely you are going to run a 10x6, 8x6 or whatever, so you will not see near as much pitch on an airplane prop that you would on a helicopter head. It's going to be big enough for 10's, so I would put 10's on it. Just watch your motor temps.

 

[Derek]

Thanks for that, Tony! Everything you said has already occurred to me, so for me to hear someone else echo what I've already thought about is reassuring.

I went to my LHS today and I was telling a few of the guys, there, about my project. One of them was very entertained by the thought. Two of the other guys there actually verbalized that they felt I was wasting my time and money. Telling me it was a foolish idea (exact words). I really wish there was a different hobby shop around here for me to visit. Let me tell you this....one of the biggest reasons "why" I want to build a 500mm 6S racing quad is because I don't know of anyone else that has one....practical or not....so what! I built a plane a few years ago that was 11.5 feet long with a 20 foot wingspan. Practical or not, it was a fun build.

Anyway....battery question....I have some 6S 3700mah 45C batteries. Will these be good enough for this quad? In my mind, I'm thinking "yes" because it's not often that I'll be going full throttle, so it won't be often that I'll be pulling max amps. The main reason why I know this is because it's not often at all that I fly with full throttle on my ZMP250 quad.