Following on from the very successful H quad with vibration isolated arms I decided to build something that would lift a DSLR or larger.
Is seems a hex has marginal chances of surviving a single drive failure so I opted for an octa. The H8 was quite an attractive layout but the loss of efficiency and lift was too much so I decided to build a flat 8. It also had to fold down to less than 35cm wide if possible. I wanted to keep a vibration isolation system but the method used on the quad was not suitable. I opted for a separate frame which carries all the heavy and vibration sensitive items like controller and camera, all suspended on silicone ‘O’ rings. Rings can be added or tightened to ‘tune’ the system. Provision is in place for z axis O rings if required but with 6 rings it each corner it is already very stiff in all axis.
I was part way through the build and struggling to get the folding arm system working nicely when my son ordered a 3d printer. I was very sceptical despite their popularity on this site.
After the first few printed items came off I wondered how I ever managed without one and my poor son didn’t get a look in – sorry Leo.
Once all the plastic parts are printed it doesn’t take very long to cut the carbon to length and assemble it.
eCalc suggests it will have a max TOW of 8kg (inc 3.3 kg payload) and hover time of 11 mins at that weight. More realistically, with a DSLR and 4 x 5AH 4s is should be about 5.3kg and 22 mins. (This is using MT4008-12 with 14x4.7 props)
I am considering a production run of these frames once this one is proven.
Comments
Hugues. Did you see my blog on the gimbal build?
http://diydrones.com/profiles/blogs/dslr-gimbal-using-3d-printed-pa...
There was still some lateral (y axis) shake on the camera so I changed the mount plate from the white solid one to a damped one. If you enlarge the picture of the underside of the copter (above) you can see the new black mount suspended on orange o rings. There are also some sorbothane pads between the moving parts to dampen movement. You can also see the new ‘cam, shaped zoom wheel.
I used a HCMI converter like this, and trimmed it down to the essentials. It’s the thing wrapped in green tape above.
http://www.ebay.co.uk/itm/18cm-FPV-Super-Soft-HDMI-Cable-Mini-Inter...
The NEX cable is this one.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=261118035614
Sorry I don’t know my Alexmos settings. It will take a while to connect up the board and check.
I am impressed with the vibration free video. To understand how your gimbal is attached to your frame and with which vibration isolation, do you have pictures or schematics?
What are your alexmls PID and power parameters for roll and tilt?
What cable do you use to output live monitoring from the nex5 without too much rigidity?
very nice Vince...
Will consider that but the frame is not so easy to make in its current form. Perhaps with the new printer I will make clip together corners for the frame. Trouble is, I keep refining Mk1. Mk2, Mk3. I should just make some to sell. People are also queuing up for my new printer which I never expected.
Testing the NEX and ginbal.
The Octa has recently been producing some nice video and stills but there were a few little jobs that needed completing.
I had intended to 3D print a cover for the electronics but the current machine is not big enough so I had to resort to my pre-printer construction technique, carbon and vacuum bag. Fairly pleased with the results. looks Ok and only weighs 40g.
This is the 5 minute fold.
And the 15 minute fold.
The video from the Sony NEX is converted by a HDMI/AV (the thing in green tape) and there is a video switch where I can select NEX or FPV HAD2 (with OSD). The NEX has remote zoom and remote IR stills/video switch.
It all adds up to a lot of wires.
Ready to go (except its dark outside)
I like this forum. We all have different requirements, theories and preferences which makes it interesting...ME TOO...its not about going fast,its about surface wind hits(props are also big surface disk)..also i always been told copter arms should not bend(one of example is autotune wont work)...but u are right about crash time,with strong arms you wreck other parts(motor wires) more expensive than arm itself...and dont get me wrong,i like what u did with your octa but things can always be better...x8 and y6 can fold much smaller and be more portable wich is for me essential when u do video somewhere in nature far from roads....
I like this forum. We all have different requirements, theories and preferences which makes it interesting.
When I built the Octa I wanted heavy lift, efficiency, reliability and low camera vibration. I didn't need it to go anywhere fast, especially during filming. Its now working very well with rock steady video at 55mm zoom.
For 'chase' video I use the quad with gopro and have just done some film for a TV cycling documentary in windy conditions.
There may be a time when a X8 etc seems the best answer but that efficiency hit is a problem for me.
Expensive carbon arms? Yes I have always wondered why other copter builders use such fat expensive arrns. My 12mm ones will take about 8x more bending force than the motor can give and should snap in a crash instead of wrecking other parts. They also flex a bit (see above video) and absorb vibs.
I dont know if one big motor and ESC is 2x the price of 2 smaller motors for the same lift. Perhaps someone else has the time to figure it out.
Y6 and x8 yes,yes and yes....y6 and x8 is far better aircraft than quad...its not only efficiency(flight time in my case only drop from 23 to 20 minutes).
If you build multi by your own less carbon tubes(realy good ones are still expensive) and motor clamps,redundancy as well(its hard but u can fly y6 withot motor and x8 without two,been there than that)
Also one important thing;if you want to use 6s batt(and i have 2 of them in paralel,2kg together) for less amps greater efficiency,and some decent camera and gimbal you will have to use some really strong motors and big props for quad.
That lead us to another problem (wich is why coaxial is better) and that is big surface of your aircraft,twice as big,especialy with flat octa.Vince,your octa is champion in that,bcs of middle part,and air resistance must be really big.in normal flight and not to mention on windy day when is impossible to have stable aircraft.
Also bcs of two motors on same arm, they have stronger push force on windy day....not to mention cost of big motors and propelers wich can make your quad more expensive than x8..(motors and ESC does not fail almost never if you solder everything well)
Guy, I tend to agree with you.
I think the octa theoretically has a reliability advantage because it still flies with one dead motor (mine does anyway) but there are twice as many to fail as a quad. What are the chances of having two motors fail on an octa at the same time? I suspect its higher than pure chance because bits could take out the motor next to it.
Also, how often is a crash caused by a single motor/ESC/prop failure? The 3.01 thread would indicate there are a whole lot of other things that are more likely to cause a crash which only increase with complexity.
All other things being equal it is more efficient to have one big motor than two small ones. What about purchase economy? I haven't checked out $/per kg lift for equivalent quality motors but I suspect that also works out in favor of fewer motors.
Y6 and X8. no,no,no. Look cool but bad efficiency.
Hex? Why? Most cant survive a motor failure so you are just increasing you chances of having one and therefore a complete loss.
So why did I build this Octa? Well it was for reliability but my thinking has shifted slightly so my next heavy lift machine it will probably be a large quad as you suggest.
That was a long answer.
My printer is a Mendelmax 1.5 but I have almost finished a new big one that I have designed myself.
Here is a link. (The printer forum is dull compared to this one).
http://forums.reprap.org/read.php?2,264549
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