Flight Experiments: Propeller Lift
by Mark Bellis 2010

In February 2010 the LEGO company held a competition about flying models.
The aim was for entrants to make a decent model plane, but not flying for real!
For Adult Fans Of LEGO, making a LEGO model lift its own weight aerodynamically
is a more fitting challenge.  Flying comes after that!

This evolutionary experiment aims to create the greatest aerodynamic lift.
A few things are required:
- The most efficient propeller
- The most powerful, fastest motor
- The least friction in gearing
- The lightest model
- Lots of electrical power!

Boundaries:
The aim is to use mostly LEGO pieces.
For power and control, any power source beyond a feed wire is fair game.
- once a model can lift itself, look at LEGO mobile power sources.
LEGO motors only, no RC car or aircraft motors!
LEGO propellers only, no RC aircraft ones!
If paper or any other material is used, the mass and volume of LEGO bricks should be greater
Heat sources and light gases are banned (it's not a balloon!)

The scales display weight to the nearest 0.1g.
Turn on the scales and spin up the propeller to the voltage rating of the motors.
For 9V motors that is 9.15V, equivalent to 6 fresh AA batteries.
Once the propeller is at maximum speed, press the Tare button on the scales.
Ramp down the power and stop the propeller.
Read the weight on the scales, which is the amount of lift generated.
Weigh the model separately in a static condition.

The blue 3-blade propeller model:
- Uses blue panels from the Mars Rover set
- Uses two PF medium motors
- Weighs about 120g
- Generates about 39g of lift
- Needs about 1 Amp of current from the power supply (more than 6 AA batteries would supply)

The Orange 2-blade propeller model:
- Uses 2 door panels from Unimog 8110 sets
- Uses two PF medium motors, geared up 40:8
- Has similar weight to the blue panel model
- Generates 50g of lift as shown
- Allows adjustment of pitch to find the best angle for lift
- Uses a similar current to the blue panel model
- Could use more similar panels to make a better fan

When the lift is enough to match the weight of the model, the power supply weight can be
added into the equation, extending the experiment to find the lightest power source.
The Power Functions rechargable LiPo battery looks promising for this, but is limited
to 800mA output current.

I look forward to trying the E-motor and wind turbine blades from the educational sets.

Mark Bellis