Please help with some dimensions

[Gunter]

I'm going to start the design on my airframe tomorrow but need to confirm a couple of dimensions.

1. I plan to make an octo, with similar dimensions to the Droidworx frame. They state 820mm motor to motor overall diameter, which they say will do 12" props. Is this a good size or is there any mileage in going slightly bigger to fit bigger props? Or is it better to go bigger, fit 12" props and just have room to fit bigger props if needed?

2. Please could someone with a Droidworx AD8 frame measure the diameter of the round centre plate for me - I plan to use their clear dome and need to make sure it fits.

Many thanks,

Gunter.

 

[ovdt]

The diameter of DWX center plate is 185 mm.

If you're planning to use standart dome, I recommend you not to use it. It's goint to break in a crash won't protect the electronics.

You should either buy the high impact one or fit in something cheap like I did: http://www.multirotorforums.com/showthread.php?929-Another-cheap-but-yet-effective-dome-protection

Standart boom size of AD8 ise 410mm. If you use longer boom, 465 mm, you can fit 13" props. Should you? It's up to you. If you're building a heavy lift machine, it's better to have room for bigger props. But probably 12" props will give you enough lift in a octo setup.

 

[Gunter]

Many thanks ovdt. I was planning to use the high impact dome. I might be be able to get one specially made with fibreglass but I will find out next week.

Is that 185mm the same diameter for the dome as well?

Cheers,

Gunter

 

[jes1111]

I'd go for 900mm diameter, which would be good for 12" or 13" props. To fit 14" props you'd have to go to more than 1m diameter - getting a bit big! - and it's unlikely that one engine choice would be suitable for 12", 13" and 14" props.

More generally, though, you have to start by defining the weight you want to carry. If you want to carry a 5DMkII, then you plug those numbers in to eCalc and see what happens. Personally I don't quite understand the "more motors is better" approach that Froidworx seems to promote. IMO this so-called "redundancy" is a poor substitute for high quality components, impeccable build and consciencious pre-flight checking. A quad with the right motors is perfectly capable of lifting a 5DII. A hexa (Y or flat) will do it easily. Eight motors is, I think, only "necessary" for really heavy loads, above the weight of a 5DII. Just my opinion, though

 

[Gunter]

Jes, I see where you are coming from. I currently fly a quad with 13" props and I find it a bit unstable in wind. It really has to be quite calm to make a decent video. When it's calm, it flies superbly though. Although I have ever flown a 6 or 8 rotor heli yet, it still looks a lot more stable and able in slightly windy conditions. From what I can see, if you have a heavier craft, it will be slightly better in the wind...but that's just my thoughts!

I really want to build something big, maybe not with the best "mainstream" kit, but something that looks good and is capable. I will start with the Arducopter, with 30A ESC's and their 880Kv motor. The main reason is that the UK dealer lives 1/2 mile away from me and I can get spares and advice in minutes After that, I might upgrade to bigger motors and props...that's the plan anyway!

Cheers, Gunter.

 

[ovdt]

The dome size is just very close to 185mm. The important part is the center plate, the dome will fit on it if the center plate is 185 mm in diameter.

For windy conditions: I fly Hexa and Quad in 15mph wind. Hexa is also very well affected by the wind.

For roll and tilt, I find Hexa more smooth but I'm sure with small adjustments quad can fly similar. I agree with jes, I wouldn't go more than six motor.

For taking pictures, I definitely go out with my quad. For video, I use hexa setup.