A long long time since I published last time, I'm drawing something fun and I thought you would like to see it!
It is a small frame all cnc machined from delrin sheet for 5" propellers. It seems a crazy project but i have a friend flying this kind of multicopters and it is really fun!
It is not originally thought for Arducopter but I recently purchased some Ardupilot 2.6 and i am seriously thinking to install one of them here.
Dimensions (center to center)
right to left = 165mm
front to back = 145mm
HD camera: Mobius
Ipad size comparison:
Comments
Watch out as the mobius interfere with GPS until total blockage, I had a GPS block with it whe nit was 5cm away from the GPS, there's a thread about it over at RCGROUPS
Interesting info Gary. Hey, you know my interest in small quads. I would love to work with you on your idea. I don't have a lot of technical support to offer currently, but I have been doing research, making contacts, and generally cheerleading the cause. Feel free to contact me if you would be interested.
Hi Nick,
Yes prop wash on to flat arms will cause quite a bit of loss.
You get not only the flat plate area of the arms which directly counters the thrust for that area, but you also get a large area of surrounding turbulence (and reverse lift (vacuum) on the backside of the frame arm) which further decreases the effective thrust.
At a rough guess from looking at the design on this Blog and the one directly above, my guess is about a 15 to 20 percent loss of effective thrust from flat wide arms.
One reason that CF tube copters can be more efficient is that since they are circular, flat plate loss is only slightly over half what it would be for the same size flat stock.
And if you make it an aerodynamic (wing shape) in the direction of flow you can reduce the loss to less than 1/3 of the cross sectional area..
Worse, in a hovering craft such as a multicopter you are dealing with direct interference to static thrust with a structural member of the craft itself which means it is a dead loss. (Thrust statically pushing against the vehicle itself).
However, the worst loss of these tiny copters is from the small diameter of the prop that must be used.
Air is a more or less fixed (low) density fluid medium and prop efficiency favors the largest diameter possible.
The reason they work well and actually can have 10 minutes flight time is that it is possible to keep the weight so low.
The same reason insects like the flea can jump so high: "Lilliputian effect" (from Gulliver's Travels.)
Given the shrinking nature of our electronics and cameras and the increasing efficiency of brushless motors and Lithium batteries, smaller and smaller and more capable multicopters are going to be possible and practical.
Soon you may need to look twice to see whether it is a bug or a copter.
I am going to start working on the smallest design I can come up with for a quad that can swing 7 or 8" propellers because they are potentially over twice as efficient as 5" ones and it will better cope with the weight of a Pixhawk and small FPV camera & transmitter. Also 3DR telemetry radio - tablet flyable (no conventional RC receiver or transmitter).
This is awesome!
Do you think the airflow from the motors onto the flat arms will have a big effect on efficiency and/or vibrations?
@Enes ÇALDIR
Yes!, I have download from your accoun in Grabcad, thanks!
@Alex
Very similar project! Nice!
@Nicholas Witham
It is great idea, but i need a 3d printer! I have only a cnc router
@HeliStorm
Very innovative frame, good job!
I too have been playing with micros lately, they are so much fun :) In fact one of them is built around PX4, have you considered that ? It's significantly smaller than apm. Also, maybe you should re-consider VTx placement, just below gps/compass doesn't look good. Maybe switch places with Rx?
In any case good luck with your project, keep us posted ;)
@Andrew
Multicopters are inherently unstable. Having a high CG makes no difference compared to a low one. There is no pendulum effect for stability in a copter. http://en.wikipedia.org/wiki/Pendulum_rocket_fallacy
The ideal CoG is at CoR (Center of Rotation), where the least forces are needed to make stability corrections.
Looks great, I'd love one of these !
I would be interested to know whether your GPS reception turns out to be a factor, being in such close proximity to the VTX module and VTX antenna, and in the absence of any shealding between the two.
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