tricopter

AlduxTri

AlduxTri

By Aldux

A tricopter is similar to a helicopter except that it has three vertical rotors as opposed to a helicopter one.

tricopter-draw

The basic design of a tricopter includes three motors, one of which is vectored.

Components

The drive system should be configured to provide the highest amount of “thrust resolution” possible. In this context, thrust resolution means the amount of increase or decrease in thrust produced as as the transmitter or gyro instructs the ESC to change power to the motor. A higher resolution (smaller changes) allows the tricopter to make minor adjustments and fly smoother.

Motors

The lower the kv rating, the higher the thrust resolution. Motors under 1000kv are ideal for tricopters.

Arms completed
Motors and ESC

ESC

Three ESCs are required, one for each motor. The throttle of each ESC is controlled by a separate channel and has a gyro between the receiver and the ESC. This allows the tricopter to become stabilised by varying the speed of each motor individually.

Some ESCs have finer resolution when instructing the motor to change speeds. There is no documentation for this and has been found through trial and error. Please see the Successful Combos section when selecting ESCs.

Propellers

The effect propellers have on thrust resolution comes by virtue of their pitch and weight. Low pitch and low weight propellors provide the highest thrust resolution.

 

Videos:

AlduxTri

AlduxTri

By Aldux

I was a little bit sad at the end of the summer, my favorite designer had left frown, so, to cheer me up, I start building a tricopter, using a carbon-fiber frame, some powerful motors, a digital servo, some ESC’s and a MW board…

The tricopter is a small model rotorcraft with three arms, this arms can be shaped (angled) as the letter Y, T, and in between, the angle in Y configuration is 120 degrees. The Y configuration brings to the system the best performance and simplest piloting.

The yawing of a tricopter is a special case. If you are using one rotor, it produces torque that tries to spin your vehicle into the opposite direction of the rotor. A helicopter uses its tail rotor to compensate this direction. A quadrocopter, hexacopter, octocopter an all copters with an even amount of rotors are using the fact that two rotors are in the same plane, both turning in opposite directions with the same speed, are neutralising their torque.

A tricopter has two rotors that are spinning in opposite directions (or in the same direction wink) but there is a rotor left who produces torque that tries to spin the tricopter. Because of this, tricopters are usually using a rear servo to tilt the rear rotor to compensate this torque in the same manner a helicopter tail rotor does. The advantage of this solution is more yawing agility in comparison to multicopters with even amounts of rotors.

In the final tests of the maiden flight I change the angle of the arms, from \ | / to \ | | (asymmetrical arms) and I was able to fly it, but it was a little more complicated. When switching to the T configuration, the tricopter goes forward very very fast and its more hard to control and to hover it in place.

So, the main advantage of the tri is that the rear servo makes yawing much faster. And also are more agile than even-multicopters.

Thanks to Murray for sharing the maiden video, and giving me nice pointers to its dynamics.

note: in the video edition I wasn’t able to remove the words “Great Britain”… sorry for that…