Large FPV quadcopter / octacopter

[nilsen]

Hi everyone,

As some may know I do a lot of Aerial photography work and currently have a medium sized hex which comfortably lifts a gopro and gimbal however I have a larger gimbal used for NEX sized camera's and small DSLR's and already have 4225-390 motors made for 15-18 inch props and some 40 amp ESC's.

I'm no stranger to DIY so am willing/wanting to go custom on this frame but I have a question which some may be able to answer.

Traditionally when going large (15+ inch props) X quads are used or X8 or Y6 or flat octa's / hexes etc so I was wondering if there is any drawback to making a QAV500 style coaxial quad (4 arms, 2 motors per arm for redundancy) so that the batteries can be out the back and the gimbal mounted to the front instead of strung underneath?

I was looking at the X4 from tarot but it's huge however the folding arms are excellent in terms of portability but I would imagine an "fpv style" machine would have speed benefits as well as being relatively simple to make and layout.

I'm imagining the center plates housing the ESC's with the arms of about 50cm (~20 inch) in length coming out angled ala QAV500.
I imgine CF sheet with a square tube for reinforcing in the middle.

Am I missing something as to why this hasn't been done or is just a plain bad idea?

Thoughts?

 

[Cyberdactyl]

I would imagine it has been done before. Videos and photos on the internet probably only represent 1% of what has been DYI'ed.
As to doing it, I see nothing inherently wrong as long as you keep the frame stiff. And from what you said, you are well aware of the issue and are designing for it.

 

[cranialrectosis]

I think speed is limited by weight and prop size. I don't see how an FPV style frame (not sure what that is exactly) would make any difference to speed.

I think you are building something similar to the FT Avengers Helicarrier. but smaller and without the foam board.

 

[Mustang7302]

Big heavy / expensive motors, carrying big heavy / expensive batteries, carrying expensive gimbal hardware, carrying expensive camera gear and you want to skimp out with a DIY frame? With the amount of money involved; this wouldn't be a build I would experiment with, I would be looking for tried and true setups.

 

[nilsen]

Thanks for the replies gents,

by "racing quad" I mean an H-Quad but not traditional as the arms in the QAV are tilted slightly forward and backwards.

When you use traditional X quad styles you need to use retracatable landing gear which adds to weight and some complexity in order avoid seeing the camera in the view.

The only downside I see is that the frame would be quite long to accomodate the large prop.

I'm going to do some calculations and see how long it would be to get the optimal 1" prop clearance.

Thanks again.