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View Full Version : My old Octoquad!



Stuart 73
07-05-2011, 07:59 PM
Here's a video of my octoquad that i have been flying now for about 9 months,
i haven't had chance until now to video it flying, to busy flying! and building new quads!
A bit windy 10-15mph but pretty stable, only using version 1.7 shield, flight software can't remember! i haven't updated software on this quad for nearly a year now! i'll have to look into it,

http://www.youtube.com/watch?v=9Eoi0zDItHc

ziisco
07-05-2011, 10:47 PM
looks good! are u using separate PWMs and X in plus mode or just Y splitters on 4 pwm outs?

Stuart 73
07-06-2011, 02:28 PM
I'm using splitters on 4 pwm outputs in + mode!

Nikotine
07-06-2011, 02:42 PM
The battery on my quad is drained after about 10 mins. If you're flying an octo, can't you only just fly 5 minutes or so? Or do you use an extra battery in parallel because you have more lifting power anyway?

Stuart 73
07-06-2011, 03:32 PM
I'm getting around 10-12mins flying time on a 5000mah battery! because the motors are about half the power of the normal motors that i use, at hover each motor uses about 3amps so total at hover about 24amps! the octo weights 2kg and hovers at one third of the throttle, this quad is not used for heavy lifting i have got another one that i use for that which uses 4 770w motors with 14 inch props which produces 12kg of trust and only weights 2.5kg!

hokie1999
07-11-2011, 08:48 PM
Question: What is the advantage of eight motors? Is is a smoother flight, more lift, what?

itod
07-11-2011, 09:30 PM
Question: What is the advantage of eight motors? Is is a smoother flight, more lift, what?

More lift so you can fly with bigger camera, and (probably more important) redundancy - you can finish the flight with something in the one line ESC-motor-propeller broken. In theory you can even fly with two motors dead if they are not on the same side of the copter, but I haven't seen the video of something like that.

Honk
07-12-2011, 03:27 AM
Stuart, have you tried reducing prop size on your octo? On my octo I have 10x3.8 props and it gets like 6-10 minute (never counted accurately) flight time on a 3.8Ah battery also weighting around 2kg.

But the thing is that letting the props run slower (because of the "big" and more props) I think is bad for efficiency, so I believe that reducing down to 8 8" props instead of 10" props is gonna let it run much longer, because these motors seem to be more efficient at higher RPM's... Just a thought. I haven't tried it yet.

And yes, it's for redundancy, I've landed my V-octo several times with only 7 props spinning because one motor always dies first due to bad cut-off setting in one of the ESC's. Flies the same on 7 props actually! Also the other reason I think is to be able to use smaller props and by that gaining stability since smaller props change RPM faster which we need to regulate.

Stuart 73
07-12-2011, 11:52 AM
Hi Honk, the octo that i'm flying in the video has got 8x3.8 props on it, i have found that they are the best size for my octo, i.e least amount of amps required for hovering but still very stable! the motors and esc's hardly get warm, i have tried it with some 10x3.8 and some 7x6 props but the 8x3.8 give the best results! soon i will remake the whole frame out of carbon fibre to get the weight right down and use lower amp esc's using 25amp ones only need 15amp esc's for these motors but using the 25amp esc's allows me to up grade the motors with out buying another set of speed controllers, this is only a test rig, i know what you mean about using smaller props they are a lot better on this octo. I have had a small problem with one of the esc i think it's a bit lazy! have flown it with just 7 motors hardy any difference just needed to add a little trim to counter react for the loss of one of the motors! (busy waiting for a replacement to come) how are you getting on with your octo do you find it is more stable in windy conditions? i think mine is!

Nikotine
07-12-2011, 07:39 PM
Nice builds! i take it you have a cnc?
I'm planning on building one myself. Would you like to share some details about yours?

Honk
07-12-2011, 08:28 PM
Ah so you have already tried smaller props! Good to know... Did you increase flight stability or flight time by doing so? Or both?

Well, I haven't really gotten a chance to tune in my octo, but the first runs it kinda felt pretty wind sensitive, not like I had imagined, but then again I'm using too big props (I think) and as said not tuned. I think at least my strange octo needs a little more gains allover in the stabilizing PID's.

Stuart 73
07-12-2011, 11:09 PM
I noticed with the larger props 10x3.8 the octo was affected a lot more by the wind! but it was still very stable and flight times where 2-3 mins less, about 2amps more per motor!
i was surprised how well my octo flies in the wind, i was flying it the other day in winds up to 25mph plus! little bit tricky to hold altitude but i guess the wind was blowing air away from under the octo! i was also flying my other quads and my large heli and dam it was hard! but the octo was easy, octo is the way forward for me i think?

ziojos
07-12-2011, 11:36 PM
I think we have two distinct cause /effect (3+ ;) ):

1) Larger propellers have more inerthia and respond slowly to control command and need larger motors
2) Larger propeller needs more room betwen each another to avoid aerodinamic interference

Then in the radial (or H ) octo it is difficolt have room betwen large props and usualy little motors are used in reasonable size octo.

3) Too small props are usualy inaccurate