Experimental Bicopter. based on a multiwii fight control board and two motors/propeller's each able to swivel and controlled by servo's.
For this build I am using one of my favourite construction method.
1) I draw out the parts on a Raspberry PI using Qcad.
2) I print out the drawings at a scale of 1:1.
3) I stick the paper onto 3mm plywood using "prittstick". and double up as necessary (front and back, two sides)
4) Cut out the bits on my fret saw.
5) Stick all the bits together using Gorilla glue.
the last picture shows the model assembled but not glued, with this type of construction you should be able to make the model lock and hold itself together, and before I glue the model I always fit all the pieces together to make sure they are going to fit.
I just added a couple of screen shots from the raspberry PI qcad program (LibreCAD).
To add qcad open terminal and type
sudo apt-get install qcad
And if you are going to print then you will also need to install cups
open terminal and type
sudo apt-get install cups
Step 1: Putting the Bits Together.
So after cutting all the bits out and checking they fit I then in one go glued all the bits together using gorilla glue which I find very good. It only takes about 2 hours maximum to fully harden and foams up to fill small gaps.
With the main structure glued I then added pieces of 3 mm ply to the back sections where the servos will be mounted.
At the same time I glued threaded inserts into the ends of 12mm carbon tube. this design allows the tube to turn by twisting on bolts screwed into the threaded inserts in the end of the tube (the picture shows it better than I can explain it) you can also see in the picture the motor mounts pushed onto the end of the tube. at the outer end of the tube I have used a piece of fibre glass sheet to support the end.
The servos are also screwed into place. the servo used have metal gears which is a must otherwise as soon as you have a crash landing the gears will strip.
Step 2: Mounting the Hardwear.
Now its time to get all the bits into place.
To allow the motors to move they need a connecting arm, which is also made out of fibreglass and screwed to the motor mount using two of the motor screws. at the end of the arm is a pushrod fitting which holds the push rod into place using a grub screw.
The flight control board is mounted at the top, I choose this place as its near to the roll centre of the propellers. the holes to mount the board were drilled before the ply was glued into place.
With the motors and flight control board in place you can now put all the wires in and tidy up the spare cable by wrapping it around the frame.
The receiver is fitted into place using tie wraps and the connections made to the flight control board.
At this stage I decided to put Velcro strips down the side to fix the top section to the bottom where the battery is held.
Step 3: Completed Model.
So the last bits are the propellers and links from the servos to the motor mounts.
the propellers are 9" *4.7 and obviously counter rotating.
Its very important to get the neutral values correct so make sure you hold the model upright and securely and then connect the horns to the servos at as near to horizontal as you can. then adjust the link to make the motors mounts exactly horizontal and exactly the same as each other. You can see in one of the pictures that there is a connector in the connecting rod to allow for adjustment, this connector is just a terminal block as removed from a terminal strip. (we call it choc block in UK but I am not sure if that will translate!)
I put the model on the scales and it weighs in at 923g (including the battery but not the propellers)
Step 4: Flying the Model
This model is very hard to fly! it needed a lot of adjustments just to allow it to fly (PID's) And it will only fly in the calmest of conditions, as soon as the wind pushes against the model it runs out of servo travel and stops yaw control.
still it is fun and its quite an achievement getting something you made to fly!