propeller basics

✈️ 1. Basics of Propellers

A propeller is a rotating device with blades that converts rotational motion into thrust. It works like a rotating wing (airfoil) to produce a pressure difference: low pressure in front and high pressure behind, generating forward thrust.

📐 2. Propeller Nomenclature

Propellers are specified by Diameter × Pitch:

• Diameter: The total circular span traced by the blade tips.
• Pitch: The theoretical distance the propeller would advance in one revolution without slip.

Example: 10×4.5 means:

• 10-inch diameter
• 4.5-inch pitch

🔄 3. Need for Clockwise & Anticlockwise Propellers

In multi-rotor systems like drones:

• Some propellers spin Clockwise (CW), some Counter-Clockwise (CCW).
• This cancels out torque, stabilizes the craft, and enables yaw (turning).

🔍 4. Identification of CW & CCW Propellers

To identify:

• CW (Clockwise): Leading edge is higher in the direction of clockwise rotation.
• CCW (Counter-Clockwise): Leading edge is higher in the counter-clockwise direction.
• Manufacturers often mark them CW or CCW.

⚙️ 5. Factors Affecting Propeller Efficiency

Main factors include:

• Blade Number: More blades = more thrust but more drag.
• Blade Shape & Airfoil: Aerodynamic shapes reduce drag.
• Diameter & Pitch: Larger diameter moves more air; higher pitch increases forward speed.
• Material: Lightweight and strong materials improve performance.
• RPM: Optimal speed reduces airflow separation and noise.

🔄 6. Conversion from 2-Blade to 3-Blade Propellers

Why convert?

• 3-blade props produce more thrust at lower RPM, improve stability, and lower noise.
• 2-blade props have higher efficiency at higher speeds.

How to convert:

• Use a 3-blade prop with slightly smaller diameter or pitch to keep motor load similar.
  • Example: Replace a 10×4.5 2-blade with a 9×4.5 3-blade.