Thrust - Notes

Owned by Jean Allison De Jesus (Deactivated)
Last updated: 2021-05-30
2 min read

(Basic) Factors that affect thrust:

  1. propeller RPM

  2. propeller pitch

  3. propeller diameter

Notes:

  • Thrust is a force, and is measured in newtons [N]. Typical notation is to measure it in g because it is more intuitive

    • Ex: A thrust of 100g can lift an object that weighs 100g, assuming that the thrust force is pointing upwards

  • Higher Prop Diameter, Lower Pitch = Higher Thrust, Lower Top Speed

  • Lower Prop Diameter, Higher Pitch = Lower Thrust, Higher Top Speed

Rule of Thumb: Thrust (g) needs to be approximately 1/3 of the overall plane’s weight for successful takeoff. A thrust-weight ratio of 1:1 can lift an object without the lift force generated by airfoils

Assuming Propeller Speed = 1000 RPM:

 

Assuming Propeller Speed = 2000 RPM:

 

Assuming Propeller Speed = 3000 RPM

Assuming Propeller Speed = 4000 RPM

 

Calculation Tolerances (Approximately how off are they from real life measurements?)

  1. Static Thrust Calculation Tolerance: +/- 26% for 95% of all cases

    1. Ex. if calculated thrust is 1000g, actual thrust is expected to be 740 - 1260g

  2. Dynamic Thrust Calculation Tolerance: underestimated by 15~30%

    1. Ex. if calculated thrust is 1000g, actual thrust is expected to be 1150 - 1300g

 

Sources

Calculation/Excel Sheet Source Link: Propeller Static & Dynamic Thrust Calculation

Additional Helpful Site: https://rcplanes.online/calc_thrust.htm (take calculations with a grain of salt)

Modified Excel Sheet (Added “Static Thrust” Sheet)