I decided to build a completely new one, because it would have been difficult to exchange the round tubes. Another point was to keep it simple and more beginner-friendly with a almost symmetric design. Although the square tubes are much heavier, the weight should be about the same as of the first design (~1.26 kg). My intention is to make multiple holes to mount the motors. So I can try different sizes and look how stable they act. Let's see if this design will fly better...
Yeah! It is flying! But the missing rigidity of the frame seems to be a big problem. Every time it lands, the motors turn slightly. As a result the copter is constantly yawing with different strength/direction. Tuning the parameters of the KK2 board is not possible and makes no sense before the motors are better fixed. We also thought that the vibrations of the copter may disturb the KK2, but it seems fine if we damp it just a little. The swinging right and left of the copter was probably a result of too wobbly damping (really not sure about this). I will upload a short video here soon. After a few hops on the grass it finally happened: The copter rolled to the side and smashed into the ground. Surprisingly the only damage was a bent aluminium tube and not as expected a broken prop or shattered PMMA parts. Unfortunately testing was still over. By the way, take care of the direction of the props! One prop has already a small crack because I forgot to check the rotation direction of the two back props. The copter nearly flipped when I tried to take of. Next step is to improve the rigidity and some other minor things. Right on the way home I bought some aluminium square tube.
On my actual project the quadcopter I'm working together with a classmate. As we were fascinated by some movies found on the web, we decided to build our very own copter to film our world from the sky. This post should just give you a short overview of what we did so far. The world of RC was completely new to both of us, so we had to do quite a bit of research. We calculated our setup with the xcopterCalc and designed it mostly with Inventor. Some data:
The RC parts were ordered from HobbyKing. The main idea is to build the frame out of CFK, but as this material is fairly expensive and not so easy to machine I decided to make the first prototype out of PMMA and aluminium tube which I found in a local store. The white parts were printed in my 3D printer out of ABS and the PMMA parts were milled on my CNC router. I'm using Cura (Ultimaker) to generate G-code for my printer. It is free, easy to use and incredibly fast. For my router I'm using CamBam. Milling PMMA without cooling can be tricky. A single-toothed cutter (diameter 3 mm) at about 16k rpm with a feed rate of 250 mm/min made it for me. A higher feed rate may be possible but my machine isn't as rigid as I wish. Assembling the parts was more difficult than expected. The double-faced tape between the ABS parts and the aluminium tube was really annoying. Another solution may be O-rings to give the clamps more friction and damp vibrations. But after fully assembling the copter I think they are unnecessary as the electronics have already damping balls. Anyway the motors can still rotate slightly around the axis of the tubes. The surface of the 3D printed parts is not very smooth, as a result there is a lot of pressure needed to clamp the tube enough. So we may have to use square material rather than tubes.
Hi all, my name is Felix, I'm 23 years old and currently studying mechanical engineering. In this blog I want to show you some of my projects which I'm working on. May it be mechanical stuff, software, electronics or all together.
On my workbench you will find a small lathe, a drill press, a self built conventional mill, a self built CNC router and a 3D printer. Through studying I have also access to a variety of professional software (CAD etc.). I really like to help or hear what you think, so feel free to ask, complain, suggest or whatever you want. Before I forget: As I'm Swiss, my English is most likely not perfect. So contact me before you get crazy because of a mistake! |
AuthorFelix Z., 25, mechanical engineer. Fascinated by: CNC, computers, electronics, software/games, scale models, 3D-printing and a lot more Archives
December 2015
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