# Calculation principle for drone frame sizes

drone frame sizes determines the diameter of the propeller, calculate the straight line distance between two adjacent axes, which is the distance of the AB line in the figure, and the distance of the AB line is just the maximum diameter of the propeller. drone frame sizes

# Thinking: How to calculate the distance of AB?

To find the distance of AB in a triangle, use the cosine theorem.

For any triangle, the square of any side is equal to the sum of the squares of the other two sides minus the product of the cosine of the two sides and their angle

formula: It can be seen that the wheelbase is a four-axis rack with 450mm. 1 inch = 25.4mm

318.20 / 25.4 = 12.5 inches

Therefore, the maximum propeller diameter obtained is 12.5 inches.

The actual propeller diameter cannot be exactly equal to this value, otherwise the two propellers will fight.

Most of the propeller diameter specifications are integers. It can be known that the maximum propeller diameter supported by this rack can be selected to 12 inches.

# Common racks support maximum propeller diameter

According to the force table, we know that the larger the diameter of the propeller, the greater the efficiency. If it is to obtain the maximum flight time, try to use the largest diameter propeller supported by the drone frame sizes. If you want to diy drone, recommand a drone diy web, droneassemble.com, you will find different drone frame size for multi-rotor, fixed-wing and VTOL.

# Baby shark VTOL 250 Fixed wing drone frame size Specifications:

KIT frame material: carbon fiber Composites
Wingspan: 2.5m
Frame Weight: 2.68kg
Fuselage:Composites
Total Weight: 5.5kg(without battery)
Max Take-off Weight: 12kg
Max Payload: 6.5kg(including battery)
Max Flight Time: 2.5 hours
Max Speed: 100km/h