I'm scratch-building a new Octocopter, in the style of the Hashcopter, using square aluminum tube, and eight motors ganged as pairs with (Quad) Arducopter software.
Where is a good place to learn the factors and trade-offs in Quadcopter frame design? How long should the arms be, and what are the pros/cons of different lengths?
Should the craft be as tight/small as possible (props near, spaced evenly), or is there a benefit to having the motors out further from center?
Any tips for optimizing arm length?
ah sorry, thought you were talking about a quad and hashcopter is just a name of a fancy control board
Are you talking about using 12 bar segments or 4?
One thing I like about the hash: I'm fond of the idea of keeping the quadrilateral folding mode intact. Assuming you can get wide enough square tubing that you're not compromising structural integrity, and you keep the tubing whole from one end to the other, use a simple vertical bolt at each of the four crosses for connection, and 1-2 rigid diagonals across the center which hold the weight of the electronics and at the same time stabilize the quadrilateral in a square. If you set it up this way, you would remove one single bolt, and then fold up *the entire helicopter* into a thin shape about 140% of the m2m distance long. You could then pack the whole thing securely in a postal tube or a 6" sonotube.
For wide-angle AP (my area of interest), you can do things like mount four cameras directly to the bars facing down with a pre-adjusted orientation, so with cheapo consumer cameras you're filming a cross pattern 120 degrees wide.
It seems you are taking this design step further than I did.
I have flown a MK octo with i2c escs and my hashcopter with quad code + pwm escs, I must say hashcopter is still not as sophisticated as a "real" octo. In some situations(descending, taking off) Arducopter still has some improvements to make. However differences are very small and Ardu is improving.
Some of the difference might come from the fact that my motors are acting as pairs instead of being controlled individually. I have some slight yaw unstability with hashcopter but this is so mild i cannot say if it is due to the design.
Of the frame design I think biggest issue is not making it too big. This because when motors get too far apart their ability to yaw the copter weakens. But at least with my 80cm frame this is not a problem. It yaws quite fast.
How about a look of MK frames: LINK. Those are so far the best flying octos to be found. Those seem to be designed as small as possible with only about 10mm between props.
How would it work if you make propellers in different level and make them slightly overlapping each other? This way you could make the frame even smaller.
"How would it work if you make propellers in different level and make them slightly overlapping each other? This way you could make the frame even smaller."
trust me, don't do this. the tips of ech propeller move in and out of another "propeller zone" which will cause heavy vibrations and therefor an unstable flight behaviour
I need a diagram on autocad dwg to cut the machine plasma, need a scheme octocopter.se Would anyone can help me thank.