A rotary wing aircraft that I can fly outdoors has been something that I’ve been wanting to try for a little while, I even priced up the required items to build a quadcopter on hobbyking, but then procrastinated about buying it until I spoke with Scott who fancied building one too. So I ordered 2 full sets of kit so we could both build one each.
The shopping list I had for each copter was:
1 x Q450 V3 fibre glass frame
1 x Hobbyking multi-rotor controller V3.0
1 x QBrain 4 x 25amp brushless ESC
4 x Turnigy 1000kv D2830-11 brushless motors
1 pack of 4 10×4.5 slow fly props clockwise
1 pack of 4 10×4.5 slow fly props counter clockwise
It all arrived, so I built up the frame putting a drop of thread lock on each of the screws, and attached the 4 motors to the end of each arm, again with thread lock. I connected each motor to the speed controller, and just to check everything worked plugged it into the controller board and receiver and powered up… Nothing happened… So I thought I’d better read the instructions. First the speed controller required calibrating to the radio, setting the top and bottom of the throttle throw. So I did this. The instructions for the hobbyking controller board were ‘sparse’ to say the least, I eventually found by trial and error that setting the throttle to lowest and the rudder full left seemed to initialise the controller board, then every thing sprang to life. I now know this is ‘disarming’ the nav board… As opposed to arming which is done by moving the rudder to the right. Still none the wiser as to what that is if anyone knows?
Of course the first thing I had to sort now was the order of the motors, this was actually in the hobbyking instructions, but the firmware which shipped with the board was for a quad with a motor in front, behind, left and right. I wanted an ‘X’ configuration with a motor front-right, front-left, back-right and back-left. Fortunately I had a USBasp connector to update the firmware on the board, so when I eventually found the firmware update utility I update this to the X configuration from the hobbyking site, change the order of each motor to its connection on the controller board, powered up, put in left rudder to start the board and then a little throttle. This time all the motors appeared to start, and adding aileron and elevator appeared to speed up and slow down the motors as I would expect. All is going well, next was to check the motors are all spinning in the correct direction and with a helpful little image in the instructions this wasn’t too much of an issue by placing a finger on the side of the motor case to see which way my finger was pushed, then reversing 2 wires if it was spinning the wrong way.
So next is attaching all the bits to the frame. Reading advice from other copter builders all seem to say that the controller board needs to be damped from vibration, my setup with the single ESC would seem to be advantageous in this situation since I could attach the controller board to the top of the ESC case using foam tape, then the ESC to the frame using foam tape the weight of the ESC should then help to damp the controller board from the vibrations in the frame. Although the heat management may be affected by attaching this to the ESC. We shall find out the effect soon anyway.
So after tidying up all the cables and tying them down this is what my copter looks like:
At this point I got a little cocky and decided to spin it up with the props attached to see if it will shuffle around the floor in the correct directions, yaw the right way, etc. So I put a little bit of throttle on, not enough to take off, but enough to start taking the weight, then just touched the rudder slightly and the copter launched and smashed into the TV. After I extracted it, I removed all the props again (replaced the broken ones) and turned all the giros to minimum, and reduced the rates on my transmitter to 50% (with the dual rates switch set so I can increase this if needed) and put some expo in too. Strangely the pots on the board seem to need to be turned clockwise to reduce the rates. Turning them this way gave the lowest change in motor speeds for any given input, this way seemed a little counter intuitive to me. But I now felt confident again and being even more careful now I put the props back on and tried again, this time success, although there is a lot of effect from the walls and floor generally it seemed to shuffle in the way I expected.
All put together, this is now how it all looks:
I still need to put a bit of tape on the receiver antennas, but next stop… a field test.
At the field we noticed that the single cable that I’d seen used elsewhere actually cross connected the Ailerons and Elevators, although we had set everything up so that the motors were working correctly of course the controller board didn’t have the motors set up correctly, so the first test flight was extremely unstable, the giros sending the copter more and more out of control. This was corrected, we then needed to add a significant amount of trim on various axis, but after this the copter took off and was controllable, but still a little wobbly. We turned up the gain on the giros on the controller board, this improved stability, this is the resulting flight by Mr Scott:
I then flew a little higher and further, caught a bit of wind which started it swaying, because it was a bit further away it was difficult to tell which way it was swaying. I should have simply left it to the giros to sort itself out, but instead I lost my cool and knocked the power down which then made things worse and ultimately led to it crashing
But I do take a lot of positives from the days testing. We managed to get some genuine flying time, the copter performed well and we did get a lot of information that we can take forwards and improve them and do better next time. And Scott managed to do all this without smashing his up which is even more of a plus so he can take it forwards without too much work.
Good fun… needs a bit of work 🙂
I mounted the FPV and OSD removed from the catalina when I updated to the Ardupilot, the following was flown Line Of Site, but recorded from the Ground Station