Propulsor Zero -Progress 11-21-2016


Since 10/2/2016, I’ve been sedulously on the Propulsor Zero project!

What are the biggest so-far-passed milestones? Keep reading.

I developed a propulsor blade analysis program.

Using Python, and multiple traditional propeller blade analysis mathematics, I’ve created a propulsor blade analysis program. It is super tightly coupled with XFOIL, a fantastic airfoil section characteristics prediction program.

The program’s name is Sherlock: Study In Scarlett (Sherlock-Scarlett for short)The part of the program doing more heuristic / high-level computing is called Sherlock, and the actual blade analysis code is called Scarlett.

The basic control flow:

  • Inputs: Span, Airfoils, Type of Run (how many sections), RPM, Altitude
  • Inputs are interpolated at many discrete sections along the span of the blade.
  • These sections are stuck into XFOIL, which spits out coefficients of Lift & Drag
  • These coefficients are plopped into two individual analysis techniques for propeller blades – the blade element momentum theory, and Goldstein vortex theory.
  • Outputs are mixed to output the most accurate estimates (empirically determined weights, compared with data from external sources)
  • These final estimates of Thrust, Drag, and Torque are put into a big SQL Lite database with all the runs

It’s quite nice to have this SQL database, since I can do big selects through the data, to find the runs with the best convergence and best force efficiency (thrust/drag). Pretty cool to harken back to the hard work I did for Veritimo in SQL. Strangely nostalgic 🙂

I designed test stand and ordered all the parts.


To better verify the Sherlock-Scarlett program, it is time to actually test some stuff.

I designed a test stand, able to measure Thrust up to (& beyond) 1000N and Torques up to (& well beyond) 20Nm.

I bought a 1.5kW AC induction motor and a 2.6kW variac (voltage controller).

The stand will have the following additional features:

  • AC Current Measurement up to 30A
  • 2 Load Cells S-type per beam
  • Steel construction
  • Vibration Measurement
  • Optical shaft encoding

I 3D printed four blades & a hub

Using PLA I printed 4 of the best performing blades (as predicted by the Sherlock-Scarlett program).

2016-11-20 20.55.22.jpg

Polylactic Acid, or PLA, being one of the lowest tensile strength 3D print filaments, will need some reinforcements to be spun with high load @ 1800RPM!

Therefore, I’m fiberglassing the blades with 2 plies of alternating bi-directional fiber direction (0deg, 45deg).

2016-11-21 07.39.26.jpg

Depending on the results of initial tests with 2 blades, I may go to 4 or 8 plies.

The airfoils are : E-63 at root, and Clark-Y at tip.

Stay tuned!



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