Hi,
(Warning: blabber on first paragraph, actual build starts after the first picture)
I have been a huge fan and follower of the FliteTest community and I thought I would take some time to give something back. Before I start I would like to thank FliteTest for sharing so much detailed information about scratch building and making it easy for someone like me (a complete beginer) to get into this hobby. I am a Programmer by profession and I have been able to scratch build a number of rc planes and multi rotors and fly each one of them successfully. The knowledge base that is available here gave me the courage to start thinking about scratch building rc aircraft. So my first article was a simple tcopter build, which was my first attempt at multi-rotors. My second attempt was an H-quad, again I didnt use any referrence for the dimensions, just keeping all motors spaced apart and equidistant from the center. This was an excellent performing multi-rotor, This is what I used to learn flips on a multi rotor. Solid as a brick (literally u could not change its attitude in flight without putting tons of pressure physically). One day I was flying quite far away, without any failsafe programmed or gps tracker(over confidence). Bad Idea!!! As the next thing I saw was it falling from the sky(probably battery came off, just had velcrow on it). I was never able to find the crash site. I am not proud of this as I could have easily hurt someone(Always think about where you fly!!! When you fly you represent all of us in this hobby). I reported to all houses, shops and businesses in the area, but never heard back from any of them. Here is a picture of it, didnt get a chance to take any more:
Electronics used: Motor: Turnigy 2822/14 1450kv (originally bought for planes, but did work really well), ESC: Turnigy Plush 40Amp, Flight Controller: KK 2.1.5, Props: 8X4.7
After losing such a chunk of my investment, I was left with a 2X10A plush esc, 1X18Amp, 2X hextronic 24Gram 1200kv motors and a nanowii from my previous article. I also lost my salvaged camera from chinese broken heli, so got a Audio Sonic Action Cam from Kmart for around $30. Luckly a fellow friend had an extra hextronic 24grams motor. So I decided to build a lightweight T-copter before I had money to buy more RC goods.
I decided to write an article about this tcopter because it turned out be quite a lot of fun to fly. Gave me about 8 mins of flight time on fully charged 3S 2200mah battery. Here is what it looks like:
Now this picture was taken much later when my HKpilot Mega Mini just arrived(So initially I used the nanowii).
I dont have a copy of the exact settings as it was when I made it, so here is how you do basic PID tuning.
- Choose 1 axis (pitch, roll, or yaw) at a time.
- Start increasing P gain until you see the whole frame oscilating(shaking), then reduce by 20%.
- Start increasing I gain until the frame starts oscilating(at a slower rate than P gain), then reduce by 20%
I left the D value alone. This will get you to a point where you can start to fly the aircraft and do the final adjustments. Do a quick google search on PID tuning quadcopters and you will find a lot of information that will quide you through it. You will not need as much P-gain on yaw axis for tricopters as you will for quads(atleast thats what I have noticed).
Other settings on the config.h file:
-Make sure you change the servo refresh rate, suitable for your servo (I was using a corona digital servo with 300mhz refresh rate)
- Make sure you check(without props on) which way the servo is correcting for yaw. If you push the tail left, the servo should turn the motor to the right to compensate. If this is happening in the wrong direction, change the "yaw_direction" on config.h to 1 or -1 as per requirement.
- Make sure you have all ESCs calibrated.
With the servo instalation, I drilled a hole into the arm, put a long screw with double washers to allow movement. The motor is sitting on a small wooden plate glued to small bar that is held with the screw to the arm. I also used a metal servo arm that I had laying around and screwed it to the bar that holds the wooden motor mount. I used .9mm fencing wire(cuz thats the only one I had), twisted and connected it to the arms on both side. I also tied those 2 up with another small piece of wire to stop the cable from flexing outwards. Here is what it looks like:
Again this picture was taken later when I had got some NTM motors to test with this setup.
Also added some landing gear (as I was landing on my battery and servo), much later, using wire clothes hangers and a piece of wood at the back for simplicity:
Here is a top view of the frame with only the back motor and servo on:
Frame Specs:
2 x 12mm x 12mm wooden beams at 53 cm long for front beam and 43.5cm for the rear beam.
2 pieces of 5mm thick sheet wood, 8cm x 8cm for bottom and 8cm x 6cm for the top
4 screws to hold the arms in along with hot glue
The center of motors are 54.5cm away from each other.
I bolted motors in along with zipties on the side arms to make sure they dont come off.
You can probably scale it down to the motors being 40cm away from each other, if not even smaller. This calculator comes in handy when designing t-copters: http://tcoptercalculator.co.nf/
I have keep changing electronics on this frame to try and find the sweet spot. I would say that my initial setup was actually not too bad. I did have some vibration issues on my first flight as seen on the video camera. I am pretty sure more experienced builders can easily iron them out, using foam for vibration reduction, etc.
Electronics used as of first flight:
Motor: Hextronic 24 gram 1200kv x 3
Esc: 1 x 18A Turnigy plush, 2 x 10A plush(I recommend using atleast 15-18 to be on the safe side)
Flight Controller: NanoWii from hobbyking
Servo: Corona Digital Metal gear with I believe 4.2 kg capacity.
Props: 8 x 4
Here is the unedited video of its first flight. I also met some fellow hobbyists at the field. I recommend playing some background music and muting this video if you dont want to hear motor noise. This flight ended with my battery running out, thankfully close to the ground. The tricopter was in acro mode the entire flight, I am sorry for not sorting out the vibrations.
Thank you for having enough patience to read through this whole article. Please forgive any spelling or grammer issues as english is not my native language.
Again a big thanks to the flitetest community and staff for providing the knowledge for anyone to be abe to do something like this. I hope that this article helps more people to enjoy this hobby as much as I have. If I have left something out, or if there is anything else you want to know, just leave a comment and I will reply.
Cheers
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