The Tricopter Saga

After building the first tricopter, I found some things about it that I didn’t like.  The body was small and doesn’t allow for much electronics.  Because of that, the flight controller, camera gimbal, receiver, and battery are all hanging off of it somehow or stuck to it with double sided tape.  I wanted something that would have a place for everything and protect it if possible.

I came across the Simple T-Copter design from simplecopter.com which has the flight controller and receiver recessed int he body.  Great idea.  What I wasn’t so much on was the “T” design.  It seems like the center of gravity would be off.  As a compromise, I made a hybrid of the tricopter v2.5 and the T-Copter.  Ideally, two bearings would inset in the platform with a matched shaft drilled into the boom, but – we’ll see if those parts turn up.

This design was pretty nice.  The platform on the front allowed me to add a camera gimbal (I used the “super simple gimbal”).  The copter flew well, but when I finally got a GoPro, the propellers were in view.  *sigh.  This called for something with the camera further forward to get the propellers out of frame.

Version three was based off of the T-Copter design.  One thing the designer claimed is that the props are out of view when the camera sits on the front.  This is true. Video looks good with no propellers in frame.  Design note: keep the GoPro directly between the propeller center.  I failed to take many pictures of version three which is unfortunate because I was proud of how I integrated the gimbal (SSG) into it.  I kept the camera mount on top, but the servos were on the bottom with an extended  fuel line going through the body.  I had to add some wire inside the fuel line to keep it rigid through the body, but it worked!

The T-copter design was great.  As long as you mount the battery to the rear, the center of gravity isn’t too bad.  It was not as stable on high throttle as the original tricopter.  I also experienced some jitters with the gimbal that I think were due to the extended fuel line tubing used to attach the platform to the servos catching on the holes in the body.  I want to build another, but the next one will keep some arm angle, have the gimbal detached from the main platform, have all electronics inline with the FC and receiver recessed, and have a designated place to strap the battery.

My next model will not have the steering mount yaw mechanism.  While this seems like a good idea from RCExplorer, I find that if my motor has any vibration, it can resonate due to the “looseness” of the extended joint.  I think the method of using a bolt or screw through a wooden platform, then attaching a servo to the platform, is going to prove a more stable mounting solution.  This was the first mounting method by RCExplorer and the method still used on the T-Copter.

The body is two similar pieces with the lower piece having an extended platform on the tail to mount the battery.  I guess it could be smaller, but the surface area touching the battery makes me think it’s more snug.  I used 1/2″ spacers/risers to separate the two body plates and attached them with  4×1/2″ screws.  Two openings in the top piece allow for access to the KK2 board and the receiver.  Simple triangular pieces attached to the arms allow for a decent looking landing gear.  The motors are no longer DT750’s.  Instead, I upgraded to SunnySky 2216-12 800kv motors.

What I’ve learned after the fourth copter:

  • The gimbal jitter was not from having extended tubing.  It’s the darn servos! Apparently this is a widespread problem and finding servos that don’t bounce around is difficult.  I tried a torroid ring on my signal line which made no difference.  For now, unhooking the servos gives me great ideo, but I have to deal with the flight movement.
  • You get what you pay for. While the DT750 motor is great and efficient, it takes forever to get balanced properly.  The SunnySky motors bolted on and with about 5 minutes total of dynamic balancing, DONE.  Smooth out of the box.
  • Be careful not to set your “P” too high on Yaw.  If it starts going back and forth, it gets nasty!
  • Don’t integrate a gimbal into the body.  Make it attachable by some means.  On Gen. 4, I used four fuel line pieces on screws to add some more vibration isolation, but the main point of keeping it separate is so you can make changes without modifying your body.
Advertisements