Tricopter configuration for Futaba 10C
With a few flights under my belt now I'm starting to get a feel for what needs adjusting. Below are photos of my current config. They may not be the final and best but it's better than my initial settings where pitch and bank were way too sensitive and I dialled back the gyro gain / throttle curve.
Here are a few points garnered from rcgroups worth considering for optimising balance of the tri;
- I have weighed my tri at each boom and moved things things to suit.This balancing made a big difference.
- I found it really important to get the swash mix for the elevator and aileron right. As with a heli the higher the value for these two will make it more touchy. This will change from model to model but mine are set fairly low. There is definatley a "sweet spot" for the setting. I went too low and it became tough to fly.
- Also I powered my tri up ready to fly then increased my gyro limits one at a time with my throttle at zero until my motors just started to turn then backed them off until the motor stopped.
- And, of course, dialled in some expo on the elevator and aileron.
- Also some expo on the pitch helped with hover maintenance.
- Then it was suggested that I balance the props.
- The numbers in the SWASH MIX menu do nothing more than control HOW MUCH TOTAL MOVEMENT you will get for AILERON CYCLIC, ELEVATOR CYCLIC, and COLLECTIVE PITCH.
Tricopter troubleshooting
Feeback from rcgroups suggested the bullet connectors could be a likely source of motor dropouts I was experiencing. I decided to re-solder the 3mm bullet connectors on the troublesome ESC and give it a whirl. Unfortunately on powering up, the motor still stuttered and wouldn't turn. Time to swap the ESC.
My spare ESC was in use in my eHawk 1500 which also happened to have different connectors (1.5mm bullet and JST). It was quicker to pull the heatshrink off both ESCs (the suspect and replacement ESC) and remove the wires at the PCB end rather than re-solder 6 bullet connectors, 1 JST and 1 XT60 connector. With all the swapping of motors and ESCs I've been doing to troubleshoot, I have a number of cable ties still not trimmed short. I've been using the releasable cable ties which I found to be pretty good. Picked them up from Officeworks.
Another test flight and it looks like it was the ESC after all. I've put two 2200mAh batteries through it and not once did the motor stop. Well not until I crashed it and broke the yaw mount.... again. I must find a better way to mount that motor. Or stop crashing.
Once I get the hardware sorted out I can move onto fine tuning it, then the Arduino controller, then maybe one day, mount the GoPro.
KK Multicopter crash compilation video
My tricopter is far more fragile than this little beast.
kk multicopter - crashs from warthox on Vimeo.
Tricopter troubleshooting
If the motors are numbered 1, 2 & 3 in clockwise order starting with the rear yaw control motor as '1', then today I swapped motors 2 & 3 to troubleshoot the number 3 motor stopping dead intermittently. I found that the problem did not follow the motor after I swapped them.
The next suspect is then the #3 ESC and it's soldered connections.
Luckily my eHawk 1500 uses an identical Hobbyking 15-18A Super Simple (SS) ESC so I'll swap that for the tricopter suspect ESC. The downside is my eHawk uses JST connectors so I'll need to solder an XT60 on the battery side and some 3mm bullet connectors on the motor side.
Hopefully the result will be a stable setup so I can focus on learning to fly it and get the Arduino board setup.
Tricopter Flight test
I've got a couple of flights under the belt now but there's a persistent problem with the front right motor. It keeps stopping dead. This isn't so bad when its 30cm off the ground but when it's a few meters in the air there's potential for more damage. I caught one crash on the trusty little keychain camera, one mounted on my hat and the other mounted on-board the tri when the motor failed.
I checked all the connections, added padding to the gyros for vibration dampening and re-calibrated the throttle and tried again. Unfortunately the same result with that motor stopping mid-flight. I pulled out the trusty iPhone 4.0 and captured some video to help diagnose the problem over at rcgroups.
I've decided it's probably a dodgy motor or maybe the ESC. The motor is out of stock at HobbyKing so I ordered a virtually identical one from lowpricerc.com. At about six bucks each, I considered ordering three to make sure I have identical motors all round but when trying to order them, I got the "out of stock" error here as well! Turns out they had two left so I snapped up both. I'll replace the dodgy motor and keep one spare.
Just in case I grabbed a replacement ESC to help troubleshoot the problem. I went with the Turnigy Plush 18 Amp ESC because I already have the programming card and when I originally bought all the parts, this is the ESC I wanted to use but it was out of stock, surprise surprise.
So now I wait for my replacement motor until I try again. In the meantime I'll go learn some Arduino programming so I can get rid of the 4 HK401B gyros and use the Wii sensors instead. Apparently the Arduino controlled TriWiiCopter is more stable.
Tricopter build: Hooking it all up
Once all the soldering has been taken care of, it's pretty much a case of running all the wires making sure they can reach and connecting them all together. I followed the diagrams shown below. I don't take any credit for the diagrams. I found them by searching through the rcgroups.com forums and in particular this thread here.
Channel 1: Gyro #1 input.
Channel 2: Gyro #2 input.
Channel 3: Gyro #1, 2 & 3 sensitivity input connectors.
Channel 4: Yaw Gyro #4 input.
Channel 5: Yaw Gyro #4 sensitivity input connector.
Channel 6: Gyro #3 input.
Channel 7: BEC input.
Channel 8: LED light strip switch.
The photos below show the wiring before I tidied it up and also swapped the Futaba R617FS 7 channel 2.4Ghz receiver for an OrangeRx Futaba FASST Compatible 8Ch 2.4Ghz Receiver from HobbyKing. I needed the extra channel to make the LED strip switch on and off from the transmitter. Next I'll go through the programming I used for my Futaba 10C radio. This is my first "Heli" setup so I'd be surprised if I get it right first time.
Tricopter build: Wiring harness
I used 14 AWG wire to make the wiring harness connecting the ESCs to the main battery (3S 2200). This is the first project I've not used deans plugs in preference for the XT-60 connectors. Deans plugs were difficult to pull apart and expensive in comparison. To measure the length of wire and get the harness in approximately the right lengths, I started the build from the out tip of the arms and worked my way in. Start with mounting the motors, hook the up to the ESCs, then lay the main power harness wires out such that they all reach back to the probable location of the main flight battery. Once all the wires are cut to length, solder up each of the connectors.
Tricopter build: Yaw control
I've gone with a 1/4" carbon fibre rod inserted and glued into the pine arm. The last 40mm of the arm is left to rotate freely on the CF rod. See this post for further details.
**This configuration will prove to be "not up to it" when it flips on a test flight, the screws in the control arm caused it to split and break free. I'm about to redesign and build something new for yaw control.
Tricopter build: Mounting the motors
The base is cut from 1/4" ply and the arms are 12mm x 12mm Tas oak about 20" long. Excuse my interchanging metric and imperial units but thats what you get building from forums in the US. I'm using a method described on the mongrelgear.com.au site for mounting the motors which is simply cable ties and a bit of glue. I found with the spacing of the motor mount holes and the bend radius of the ties, I needed to insert some carbon fiber rods to take up the slack on the cable tie. By the time it's all finished, the motors are mounted securely, quickly and easily.
Tricopter build: The parts arrive
The main box of goodies has arrived from HobbyKing. The first thing I'm going to do is solder all the connections on the motors and ESCs. I found this handy little guide that mongrelgear provide with their tri-copter kits.
The motors arrive as shown on the left in the photo below (no connections). You need to solder the connectors and apply some heatshrink wrap.
Tricopter motor from Hobbyking