My powerful V3 Tri

Great thanks to David for creating this great set.

My first tri was a monstrous V2.x, with 50 cm long arms of 12mm x 21 mm pine. My wishes for the tri was to have GPS functionality,  so I ended up with a HK Pilot Mega 2.7 with an UBLOX Neo-7M external GPS and compass. First flight with this one really showed the potential of the tri – it flew very nice with no tuning needed in the HK Pilot Mega 2.7 with the ArduCopter V3.2 firmware. When David opened his web shop, I managed to get hold of one signed version of his frame kit. It has been fun moving all parts from my first tri to this new, smaller frame. Except, I managed to “let the smoke out of” my HK Pilot board, so I had to order a new one. To be able to have more control of the status of the HK Pilot, I ordered the 400 MHz Telemetry radio set as well. Motors are the well known hexTronix DT750 accompanied with the HobbyKing F20A ESCs (SimonK flashed) and a set of 11×4.7 Carbon Fiber propellers. Powered by a 5AH 4S LiPo this gives me almost 20 minutes happy flight time on the new frame.

To make it easier to control the power to the flight controller and the ESCs,  I added two 12V 50A flip switches from Biltema before and after the  HK Mega power module. Not very nice looking, but very functional. Now I can easily power on the Flight Controller before I power on the ESCs. Emergency power off is also just a “flip of the switch away”. At the same time, I added some RGB LED strips from Biltema as navigation lights, red to the right, green to the left and white on the tail. These are bright enough to help seeing the directions of the tri even at daylight, and I guess it will be cool when I dare to fly in dark night;-) As extra landing gears, I  cut some 12mm metal bands covered by shrink tube and created some flexible rings that I strapped to the booms. These brakes any rough landings enough to save the rest of my tri from worse damages;-)

Finally I made a cockpit of 2 mm Plexiglas to protect the electronics. In addition it gives quite a nice touch to the tri.

This all looks good, but I have found a couple of minor problems. First of all,  when using such a huge battery,  the wires holding the battery tray could have been made with larger diameter and thus allowing better distance to the screws of the frame. 1 cm larger diameter would be perfect, so the landing feet would need to be higher as well. As it is now, I had to turn the screws upside down so that my huge battery is not damaged by the screws.

Second is that I had to make a bigger front piece for the frame in order to strap the GPS pole securely without having to drill a hole in the nice frame (I learned the hard way on my first, wooden frame, that GPS mounted in a drilled hole will brake something at a crash;-) My new front piece is wide enough to allow putting on the cockpit and then strap the GPS pole to the front piece outside the cockpit. It would be nice having such a wide front piece as an option from David.

Third is the sharp edges of the carbon fiber arms. You all should ensure the cables are protected by some type of rubber so they are not cut when you crash.

Four,  one day my tri started yawing on centered stick and I was not able to get it out of the spin even with full counter yaw. After a pretty nice landing, I discovered that the servo had moved from its neutral position.  Thinking this was  an SW issue, I loosened the screw and re-positioned the tilt mechanism on the servo and took off again (yes, I’m an amateur;-). Some minutes later the same happened and I then realized  the teeth in the 3D printed tilt  mechanism were broken. I have now glued and screwed on the servo horn like on the V2 tilt mechanism. I have now learned that I was wrong in using blue Locktite on the screw, because this dissolves the plastic of the 3D printed parts. So, be careful with the mounting of the servo to the 3D printed tilt mechanism, DO NOT use Locktite, instead use a very small amount of CA to secure the screw.

Finally, I discovered that the arrow on my GPS is off by many degrees,  pointing at SE when real heading is S. Be aware of this and check your directions with a manual compass. Actually, Turnigy and the Quanum LEA 6 GPSes seem to be having the arrow printed in correct direction when the GPS is mounted as I had to mount it. Well, I finally managed to make my compass show correct direction. It is depending on a perfect calibration, WITH “auto declination” enabled and GPS 3D lock, it seems. After many attempts, I finally got it correct.

Ahh… before I forget it. Mounting the propellers to the dt750’s can be tricky. I have been using nylon lock nuts, but so far this has not been good enough. Especially when running Auto Tune on the HK Pilot Mega 2.7, the motors are throttled pretty aggressively, causing such a momentum that the nut is loosened and a crash will happen. This has happened at least 2 times, that I remember, but luckily no big damage on my tri as result of these.

You’ll find pictures of my Tri at, as well as a video from one of my test flights:


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