These are the fully 3D printed T4 (quadcopter), Mini T4 (quadcopter), and T6 (coaxial hexacopter) designs I've posted on Thingiverse.com (aside: "T" is for Tubular). The comments section on Thingiverse doesn't provide a great place for discussing designs so I've created this topic here instead.
These designs are based on a tubular arm with a vertical "I" beam running down the centre. This design seems to be very strong and rigid and all of these designs are very stable in flight.
Other common features include:
- motor wiring is routed through the arms and down into an enclosed (ventilated) power and ESC tray.
- batteries are located in the centre of rotation (T6 is designed for dual batteries).
- bevelled cable "tunnels" provide a way to route cables between the power tray and top plate.
- Top plate is designed for Pixhawk or APM flight controllers with elevated GPS.
- Bottom tray has mounting points for a Tarot Gimbal.
- Optional long and short legs include "springy" feet. The legs are designed so the 3D printed threads "wrap around" the arms which makes them quite strong for their length.
- Sketchup files are included so folks can modify both designs to suit their needs.
I figure I've put hundreds of hours into these designs with prototypes and drawing time. I'd love to get feedback from anyone who makes one. Together we can improve these designs for everyone's benefit.
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I planned to use two batteries attached to the landing skids and use the battery compartment for some of the other tech. The clearance needed in the tray would be 25mm at least. 30mm would be better.
The 2212 motors with 9.4x4.3 give 650g thrust per motor. Given the 1.8kg of the copter (take-off weight) I currently have 2.6kg thrust which is far less than double the weight of the copter (hover at 60%). 1kg of thrust less than double the weight.
The projected take-off weight for the X8 would be about 2.6kg (including two 5000mAh / 2P) vs. 5.2kg of thrust. This would give double the weight as thrust which is a way better weight/thrust ratio.
I passed all the numbers through ecalc several times playing with the numbers and it looks like I can expect a higher payload and longer flight time than with the X4 configuration (currently 13-15min / in X8 maybe 18-20min - both for smooth sailing, I'm not doing 3D flight ;-)). Also the 2212 are specified for 10x4.5 props when powered with 3S. The planned motor mounts will cope with heat better than the PLA and the X8 has way better cooling as the motors are not enclosed.
This is still my first muti-rotor copter I'm building though so I could be all wrong. I hope I'm not. I'm grateful for any inputs. Especially the motors are a concern. I'd stick with the DJI 2212 as I already have 4 of them and they seem to be nice but I'm not emotionally attached to them and would happily switch to different motors if they promise more thrust.
The SBUS-2-CPPM adapter cable arrived. :-) Looks great now. The receiver fits in the ESC tray and is almost completely invisible now.
It looks so super clean now. Not like most copters one finds on the internet that have cables and cable ties all over the place.
Thanks again for the awesome model and making it available for free.
Also I have a hint for how to setup throttle failsafe when using a receiver like the ORX R800X that has builtin failsafe that outputs bind time parameters when losing connection:
I setup my radio to go down 125% on the throttle stick before binding the receiver. Then I reset it back to 100% which gives enough margin to trigger the failsafe when losing radio signal and have the copter respond the situation by e.g. switch to RTL.
Looks great Frank. Have you had any drop outs or reduced range with the receiver down in the power tray?
No issues yet but I didn't really fly that long ranges. As a precaution I activated throttle failsafe should it run into trouble. But long range flights will have to wait until I have installed FPV (which is currently on my wish-list but will need to wait a bit as there are more urgent spendings ahead).
The antennas reach outside the drone's body as you can see in the picture:
After one of the original ESCs burnt I replaced the ESCs with a 25A 4in1-ESC and the hover throttle is now 60% at 3S and the small props. Looks like the 15A ESCs were too small which also explains why one of them went up in smoke.
I taped an old point and shoot camera (~260g) to it and the hover throttle didn't change that much. http://youtu.be/k5mLerc_dNg
Great first video - thanks for posting!
Sorry, I just picked up you are using an APM flight controller so the RC receiver signal you want to have is PPM which you connect into the APM on channel one and jumper the signal pins on channels 2 and 3 together to tell it you are using PPM. See this for more info.
The 4S battery arrived and hover throttle is now almost exactly at 50%. Unfortunately the weather is so ugly at the moment it keeps me from testing if the new battery also impacts top speed. With the 3S the flight log showed about 50kph.
I will also give the bigger props a try but they didn't arrive yet.
As receiver I use Orange RX R800X which is compatible with my DX8. It has an S.BUS out so I ordered an S.BUS-to-PPM converter online but that has not yet arrived at my door either.
Good news is the new top speed in Alt-hold mode is now 61kph. Bad news is the ESCs I got in the kit with the motors were only 15A and one of them burned today taking its connected motor to the grave. Fortunately there was not more damage than the ESC and the motor. I'm now planning to use a 25A 4in1-ESC instead.
I really like this design. I am almost ready to get flying. I went with the PixHawk, QBrain, Taranis X8R combo with some 880 kV motors. Everything is "nearly" assembled, but I am stuck at the Mission Planner calibration stage. I can't get a mavlink connection to the PixHawk. I've searched all over for solutions and cannot find anything that works. It seems like a very common problem...
Did you have any difficulty at this stage? Any ideas, suggestions? I'll post photos as soon as I have it flying...
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