Dekker Rotary Propeller

[Subdeacon Joe]

https://oldmachinepress.com/2017/04/05/dekker-fokker-c-i-rotary-propellers/

 

The patents illustrate a large, streamlined hub from which two sets of four-blade rotors protrude. The original patent stated that the ideal blade length was one third of the hub diameter. The fixed-pitch blades were highly curved airfoils of a complex shape. The angle of the blade decreased from 40 degrees at the root to 5 degrees at the tip. In addition, the blade’s cord (length from leading edge to trailing edge) steadily increased from its root to its tip.

The two sets of blades were contra-rotating. The rear set of blades served to straighten the airflow from the front set, providing additional thrust and increasing efficiency. 

The contra-rotation of the blades also helped eliminate torque reactions. Through a gear reduction, the rear set of blades only turned at two-thirds the speed of the front set of blades. Dekker also noted that the rotary blades would be quieter than conventional propellers.

Dekker’s finished C.I with its large rotary propellers. Note the complex airfoil shape of the blades.

The drive for the rotors consisted of a sun gear mounted on the engine’s crankshaft that turned planetary gears against a fixed, internally-toothed ring gear. The planetary gears were mounted in a carrier from which a shaft extended to power the front set of blades. These blades rotated in the same direction as the engine and at an unspecified reduction. Attached to the shaft powering the front set of blades was another sun gear. This sun gear turned three idler gears that turned three planetary gears against another fixed, internally-toothed ring gear. This gear train reduced the rotation speed by 66% from the sun gear (and front set of blades). A hollow shaft extended from the planetary gear carrier to power the rear set of blades. Inside the hollow shaft was the propeller shaft for the front set of blades. The rear set of blades rotated the opposite direction of the engine.

 

[Cold Lake Kid, SASS # 51474]

SO, how did it work in practice?

[Cypress Sun]

28 minutes ago, Cold Lake Kid, SASS # 51474 said:

SO, how did it work in practice?

 

When is the last time you saw one in operation?

[Cold Lake Kid, SASS # 51474]

Good point!

[Marshal Mo Hare, SASS #45984]

It is a design from the 30’s. The success of the design is shown by the number of combat aircraft which used it.

[Blackwater 53393]

It would probably be very high maintenance with so many extra moving parts.  Something in a turbine system without all the planetary gear drive stuff might produce interesting results.

[Subdeacon Joe]

The interwar period saw lots of odd things tried.  Some worked, some didn't. Some that didn't led to other things that did.0

[Abilene Slim SASS 81783]

reminds me of this experiment - GE’s unducted turbofan. 
 

[Marshal Dan Troop 70448]

Remember the "Pogo"?

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