I'm prototyping my latest design - got my motor mounts put together. Other than the plate in the middle, this is the only thing that isn't out-of-the-box... but could be made very simply if they prove to be robust enough:
Am now toying with a 4+4 octo design - with 4 motors pulling, and 4 motors pushing such that the props can overlap about 2cm at the tip, but because of the over/under design never actually come close to interfering.
This is a mountain bike wheel - for a 26" wheel - the OD measures 22.5" with props @ 24.5" diam.
(am going to try using 4 pulling 880kv motors with 11x4.7 blades, and 4x850kv with 10x4.7 blades)
The next step up using the wheel design, with similar mounts, would be a road-bike wheel which measures 25"diam. and would have props @ 27"diam.
Here is the 2cm overlap from above:
I'm interested to know what behavior I might get with this combo - has anyone tried it? Am I off my rocker? Working on fixing up the center stack now. I've flown a quad with this setup before... it worked pretty well when the ESCs weren't overheating for the hot day + heavy camera load.
Feedback very appreciated!
It's not exactly Octo... it might be at some point in the not distant future - but for now, Quad will have to do!
With the new uBlox GPS receiver, I am getting some incredible loiter accuracy... so much so that I was comfy pulling the iPhone out of my pocket and shooting a video with the transmitter largely unattended!
My original concerns that there might be too much resonant vibration seems to be unfounded - I'm happy to report! And 4 spokes seem to be perfectly sufficient to carry the central load:
Ok... I flew the octo wheel today... Set up using octo +
4s 5000 / 22/15 900Kv / 20A ESC / 9/6 Props
The craft flew surprisingly well... overall the most stable multi I have flown to date.
Mavic 319 DISC rim 700c weight listed as 595 grams...
AUW for the octo wheel, including 4s 5000mAh 70c = 2.5 kg
Waiting for the gimble... and building landing gear... pics and video coming soon.
Yeah - now that I've had a few days to think on it, my bike-wheel quad was also the most stable I've flown, too. Perhaps having the battery/receiver/APM stack isolated in the middle - suspended by a few spokes - is transferring less motor vibration to the APM? Thus smoother/stable flight? I was really impressed. Looking forward to yours, Brian!
here she is .... tested in 30Km gusts w/ gopro hero and FPV kit.. still flies nice and smooth :)
Any special trick to mount the motors and the center plate?
Weight-wise, with a ration of 3.14 per diameter, a circular design starts looking specially interesting for Octos. With larger arms the advantage increases.
Motor2Motor 500 600 700 800 900 1000 1100
Circular: 1570 1884 2198 2512 2826 3140 3454
Quad: 1000 1200 1400 1600 1800 2000 2200
Hexa: 1500 1800 2100 2400 2700 3000 3300
Octo: 2000 2400 2800 3200 3600 4000 4400
I used vinyl straps to mount the motors directly to the rim... the center plate is the standard plate from rctimer 450 quad. the APM is mounted on the top plate , which is "suspended" from the main plate (the one attached to the rim) with alloy stand off's and rubber washers...
Now I am looking thru my stuff for a 20" alloy rim for a quad ;)
I realized the largest diameter for a bike rim would be 622 millimeters.
So I looked for bigger aluminum rings. Thought of Hula Hoops.
Then I found this Hoola, just 13 EUR and 360g, 800mm diam. (have found from 600mm up to 1000mm), a flat surface (20mmx10mm) and of beechwood. Would it in your experience be strong enough?
Well... there is only one way to know for sure.... :)
my finished octo wheel...
That is fantastic! How does it fly? Any video of/from it?
I have been whittling away at my next iteration. I managed to get a hold of a 26" carbon wheel. Ideally, I want a 29", but this'll do for now (it was free - from a cyclist that put a small crack in it).
Fabricating motor mounts has been a fun project. My goal is to create interchangeable parts so I can easily swap wheel to wheel.
A little fun:
My power distribution block:
I guess we are the only two doing this....
I wonder when everyone else will catch on.
I like the tire... haha I bet it floats, and all the bits can be well sealed in the tube.