# The Structure

A project log for Sylvani

A cheap but useful drone

I am going to use the 330 ml soda can as the first structural basis of the system. I have highlighted in the image how I plan to do this.

1. First cut off the lid of the 330 ml bottle
2. Then cut the conical part of the shell of the bottle so that some (slant vertical) stripes / petals remain
4. bend the strips / petals so that they clamp on the motor assembly.

Question : what is the best shape of the petals?
Answer: This is dependant on the amount of vibration. In order to answer that, we need to know how fast the motor is spinning, the static mass of the motor + rotor, and then the amount of unbalance that appears in the rotor, so that we can create a kinamatic model.

So I first need to calculate what kind of a rotor I need.

My motor details are (I will upload as soon as I get the motor) :
I ordered cheap DVD motors, I will update as soon as I find some info on them. The worst case scenario is 1800 RPM.
I do not know how massive they are.
The Betz law on rotorcrafts says that the Force exherted on the air by the rotor ( = the force acting on the craft as a reaction from the air) is given by

• - Air Density x Rotor Area x Speed of wind at the rotor x (speed of wind in front of the rotor - speed of wind behind the rotor)

Assuming windstill, this would mean, the lift is given by the rotor pitch and Rotor Area. The actual amount of lift generated by a propeller is very complex. Nonetheless there is another way to compute the same :

• F = ω² L² l ρ sin²ϕ

ω is the angular velocity, L is propeller width, l is the depth of the helix the propeller describe. So now I can look in ebay, and find a propeller.

## Discussions 