![]() ![]() Most propellers designers can get the desired lift distribution using camber and twist, and forego the complications of using large changes in chord.Carter Aviation Technologies, LLC is an aerospace research and development firm that has developed and demonstrated new and improved aviation concepts, including its Slowed-Rotor/Compound (“SR/C™”) Technology. The three main design parameters used to get the required CL are chord, camber and angle of attack (or twist). Shown is an example of a 72in dia prop with m0.8 at the tip. Since lift is a function of speed squared the required coefficient of lift at the root is two orders of magnitude higher than at the tip. Relative airspeed at a prop tip is twice that at midspan and four times that at quarterspan, where on a wing all the airflow is essentially the same speed. This approach is extended to props and results in a wing like planform, but a prop flies very differently than a wing. Efficient wings have an elliptical (or close) lift distribution to minimize drag. Modern takes on this shape were seen in Paul Lipps' winning Reno racerĪnd in the propulsor prop of the Carter Copter. Unfamiliarity with construction and installation combines with only a slight improvement in efficiency has limited its popularity. It attempts to optimize the lift distribution across the prop to maximize efficiency by using chord along with other design parameters. This propeller shape is for general purpose use. If interested, this is the patent: Olmsted, Charles Morgan. Given that the lift equation has the speed squared, this propeller though may look nice, adds a lot of weight to an area that doesn't contribute to the majority of the thrust, so it's a design that focuses on only one aspect, like this famous comic. Olmsted’s laboratory went bankrupt just two years later. Although the aircraft was 90 percent finished, construction was never completed. In 1912, work on the aircraft came to an abrupt halt when the Buffalo-Pitts Company went bankrupt. Olmstead's own pusher plane with his signature propeller never took off (shown below), and then his lab went bankrupt too: Restoration: The 1912 Olmstead Pusher, Olmsted deemed them his "secret weapon," and felt they would add even more interest to his aircraft when it was finally revealed to the public. The propeller design was eventually used for aircraft setting climb and world weight-carrying records and appeared on the Curtiss NC-4, on the first transatlantic flight. ![]() In this case, at least one (or more) Curtiss NC-4 (shown above), among other models: Propellers like tires can often be fitted to various vehicles. ![]() The "Olmstead High Efficiency Propeller" is the widest one, 2nd from the right: Question: It's certainly beautiful to look at, but what aircraft was the Olmstead High Efficiency Propeller for? When and how was it used? Here are several other photos of similar propellers: I assume that the designer is probably Aeronautical Engineer Charles M. This unusual propeller was designed in 1918 by Olmstead Laboratories and tested at McCormick Field. There is a sign next to it that says something like (just guessing): The AFResearchLab video AFRL Tech Museum Series: Propeller Development begins with the narrator standing in front of four propellers in a sequence transitioning from wood to metal, and what stands out to me at least is a very unusually-shaped two-blade propeller whose blades are extremely wide and thick near the base and taper to a point like a short, squat twisted candle flame. ![]()
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