### Bicopter help!

I am going to build a bicopter, but I just cant figure out how to stabilize the pitch movement like the one on the following video: https://www.youtube.com/watch?v=l_rg31A_hyA

Do you need a tail?if so why?

I don't have that much physics knowledge since I am on high school. The only way I see to stabilize it is to add weight (maybe battery on a vertical position)to stabilize the frame and with the servos that move the motors stabilize the little movement it still has on the pitch.

Thanks!

#### Replies

• Welcome to the DIY community! Hopefully we'll be able to help you out.

First off, if your willing to do a bit of reading, research up on kinematics equations. There's two flavors, one calculus based and one algebra based. The're essentially the same, but the calculus "covers more bases" than the algebra. You'll also want to look up something called the "drive equation" to determine the forces generated by a moving propeller.

From there, you can apply Newton's laws and realize that if you spin two motors in opposite directions, their torques will cancel each other out and not spin the craft. Spinning one up and the other down will turn the craft in one direction while doing the oppositie will make it turn in the other. Now on to your two questions:

Do you need a tail? If so, why?

For a bicopter, no, you don't need a tail at all... especially if your doing something like a Chinook design. The Nymbus looks like it was designed to be more like an V-22 Osprey, in that it can hover like a helicopter and fly like an airplane. In the airplane mode, you do need a tail because you need elevators to control pitch.

How do you stailize the pitch movement?

The V-22 Osprey, and similar designs do this by rotating the generated thrust forward and aft. Most small UAV's don't have the luxury of "real" helicopter rotors, so they get a majority of their stability from rotating the complete rotors themselves. For the Nymbus, it looks like they get additional stability from manipulating the elevator in the rear (the top of the T looks like it can move).

You really don't want to rely on shifting your weight around, as that can potentially be more complex than trying to adjust where your thrust is going by rotating the motors or directing it elseware using airfoils.

There's been one or two Bicopters in the works here, so you might be able to get some more help and experiance from them (I'm just an EEEN student that knows Quads).

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