Xmas KRAKER

By kwadkenstine on Dec 22, 2020

21  358  11

One day i will get it right

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Jayembee67   Dec 25, 2020  
1

You claim that this is still not right, but they are getting more... "cohesive". This looks like a kit, TBH - I like the shape of the fuselage and the cowling, very slick. But still not trying out the contra-rotating setup, I see?

kwadkenstine   Dec 25, 2020 

Yes um er ! , I spent some money on this one and bought 2 frames , I will not say what frames , because the manufactueres have not built it , i say this because if a novice tried to build with this frame it would have hit the bin.
Props props props . I am in the process of doing some testing on prop configs . However as i am poor and still have not got a 8 D shot output FC . becides I know the redundancy factor works . I do not think the BF software contains the programming needed to cope with the imbalance caused when a hex or an octo drops a prop. case in point ( watch NURKS hex vid )
And I have just got 99% of the parts i needed to build my own cnc router ( a fking big one , aprox 700mm x 700mm x300mm) so soon i will be designing and cutting my own frames and prolly do it for others who ask nicely, but no more crappy half assed bangood specials , that have only ever seen a render before they are flogged to the unsuspecting public

Jayembee67   Dec 25, 2020 
1

Well, it was money well spent - this does look very neat (build struggles notwithstanding)! Oh, yes, the inevitable prop hunt. It's never straightforwards is it? But are you thinking of trying smaller props on the bottom motors? I have read that can be... a good thing, somehow or other. Or just looking for the right sized big 'uns?

And yes, I really doubt I am gaining much from the contra-rotators, other than complexity and processing overhead, and definitely nothing in the way of redundancy; if any of my X8s lost a prop, they would spin off into the sunset / ground / passing airliner I am certain. But it just felt right. And regardless, they fly so well either way!

Also, that's pretty bloody exciting (the amazing toys they let the general public have these days, honestly. When I were a lad, and all that...) A router is definitely something I would like, but I don't have a workshop space I can set up with good enough extraction - those CF fibres are asbestos level nasty apparently. I do have some chums who have designed and cut their own frames, and the end result is often idiosyncratic, but very cool, and extremely personal. That's going to be a fun game for sure - I eagerly look forward to even more craziness in your feed! :-)

Jayembee67   Dec 25, 2020 
1

Oh, also, Merry Christmas! :-D

Kstone   Dec 23, 2020  

So this a 6S rig using dual 4-in-1 ESC's?

Would be more efficient to offset the top motors from the bottom by 90 degrees. This would generate less turbulence from the top props feeding the bottom.

Still thought a 7" freestyle Octo ?!? WOW

kwadkenstine   Dec 23, 2020 

Hi um , no its 8 single esc's . It would handle 6s but i run 4s on all my rigs because the budget has a limit . Im not shure if offsetting the props would gain efficiency and increase vibrations or not , but it would increase the footprint.
Also counter rotating props vs props spinning in the same direction , is there a difference . I am testing this on a thrust stand thing that i made , no numbers just comparisons , post soon the results ,,, I will.
And strictly speaking it could be called a 8 motor QUAD , because i do not run 8 motor outputs, I have other similar builds with more detail .
I like big heavy powerful things

Kstone   Dec 24, 2020 

Far as I know of, there's a large efficiency loss due to the stacked "non Contra-Rotating" propellers not receiving the same smooth air as they would if they were separated horizontally. This loss can be as high as 25% in some cases depending on how close they are from each other, direction of spin and propeller type used.

On the other hand, Contra-Rotating (CR) propellers main advantage is that there's a neutralization of the induced torque. Beyond this there can be a small (3-15%) efficiency gain. Thus the closer the props are to each other the better the possible gain. Unfortunately, a copters blades are always in flux to help maintain its stability / orientation and thus any given set of CR-Propellers is likely not to be at the same speed at any specific moment. Which means that even under perfect conditions the system will never reach its optimal efficiency. The down-side is that the CR systems tends to be mechanically more complex and ungodly noisy in comparison to a single propeller craft of the same type.

In short.... With a 90 degree offset, the copters foot print increases to spread out the propellers disk area, thus enabling it to better grab clean air. This would not only the copter fly better but use less mAh for the same flight.

Note: There are tons of Youtube videos of University experiments on the subject too.

Here is a good example of what I meant by 90 degree offset:
https://www.youtube.com/watch?v=IIkGwwt_gqE&ab_channel=octokwadFPV
https://www.youtube.com/watch?v=RFct7MKpob0&ab_channel=RotorRiot

kwadkenstine   Dec 24, 2020 

I build them like this because i have proven that they fly with up to 4 props gone. My aim is to not lose my cameras and be confident in the ability to get home or at least not ditch in the ocean if i burn a esc. or motor, , A proper octo might cope with losing 1 or 2 props but a x octo will deathroll if it snifs a problem I appreciate your point of view and am in the process of posting some test results of counter v other and just normal , I dont even know the outcome , but what ever the result it wont have much bearing on how i build , as we are all restrained by the flyware , and i aint no coder.
In short chasing the ultimate gets you no where ,

RotorHead   Dec 23, 2020  

X8 Monster - how do you start it? Throw and arm inair?

kwadkenstine   Dec 23, 2020 
1

Hi I usually run 2 lipos , 1 on top 1 under and i sit it on a rock or a heep o dirt to keep the props free . or i just arm and wak it.
Arming mid air Steel style , would make you look pretty dumb if you flung it off a cliff and it didnt arm!!!!!

DrewFPV   Dec 23, 2020  

That's a beast!

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