Thrust - Notes

(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:

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Assuming Propeller Speed = 2000 RPM:

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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: https://www.flitetest.com/articles/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)

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