Random Aerodynamic Oddity of the Day Thread

[Piotrsko]

Ok so best case you are planning on perhaps 1500 watts max out of this if you can excite the motor properly and not melt the field windings.

I'm a bit sketchy on regen in A/C synchronous motor theory

If you go 3 phase, you can use a RC toy electric motor controller from slamazon or fleabay real cheap. If you use a brushed universal motor, those are easy to control

If you are doing recyclable parts, see if you can score a discarded battery lawnmower. They are brushed dc and about the correct size

[freebeard]

The motor/generator is a part in hand. Permanent magnets on the stator.

https://duckduckgo.com/?q=fisher%20p...e%20motor&t=hi

Here's a PDF on repurposing them:

http://cogenmicro.com/pdf/Fisher_and...ve_Motor_2.PDF

[Piotrsko]

Cool, you didn't say you had one of those. I was under the impression you had a fractional hp squirrel cage fan from a heater.

Couldn't get usable data from the posted urls. Maybe time for a newer phone.

Do you think you can spin it fast enough to generate decent power? @ 500 rpm the bar is pretty low.

[freebeard]

It all comes down to whether the props are 'in the ball park'. If this does come together, I have to prevail on some friends for a site. It's not for power but would be to document the stream flow over a year.

aerodynamic oddity: Just A Car Guy: 1937 Cadillac Series 90 Hartmann Cabriolet originally commissioned by international playboy Philippe Barraud.


A Figoni et Falaschi knockoff.

[freebeard]

http://rollerman1.tumblr.com/post/176515915969

[kach22i]

March 6, 2018
First Ride: Endura Drag2Zero skinsuits tailored for aero efficiency
https://www.velonews.com/2018/03/bik...iciency_458722

DERBY, England (VN) — Most of cycling’s aerodynamic glamor is in frame and wheel design. But Endura’s designers recognize that a rider’s body and clothing induces significant drag — up to 80 percent of a rider’s wind resistance......................

SST is only applied to the sleeves and flanks for a reason. These are two areas on the rider’s body where laminar separation — or the separation of air from a surface — can cause problems by creating a low-pressure pocket on the trailing edge of a shape. It’s the same issue that airfoil frame tube shapes address.

The silicone chevrons help reduce laminar separation by creating tiny vortices of air. Airflow then adheres to that surface longer and flows more smoothly around it. That means the air separates from the surface later, shrinking the drag-inducing low-pressure air pocket behind the rider.

The butt cheeks or at least the hips are where the silicone chevrons would be most effective, right?



I don't see any there.

Related, further in the article they mention a material used in the helmet called "Koroyd" said to be superior to Styrofoam, but no comparison to Monopan or other honeycomb materials.

Upon watching the video in the link, I suspect the inner and outer tubes can move independently to a degree based on a frictional resistance, and it is only the outer tubes that get thermally bonded together. It's not clear to me yet at this time as it's a short video with no words.

Has anyone in the forum heard of this Koroyd material before?

Thermally formed sure sounds friendlier than vacuum bagging and epoxy methods requied with Z-Plex.

Sandwich structures deliver core benefits
https://www.materialstoday.com/compo...core-benefits/

The composites industry has long known that the strength and stiffness of a composite structure can be increased significantly with little additional weight by laminating a core material between two skins. The core of the sandwich serves to distribute shear stresses from loads over a wider area and resist shear and compressive forces better than a single-faced laminate.

Innovative core materials which have proven successful include thermoformable honeycomb, conformable foam and agglomerated cork. These materials can be easily shaped to produce curves and fit into moulds. Recycled polyethylene terephthalate (PET) bottles and carpeting are being used to produce cores that can lower the cost of composite structures. And renewable bio-based polymers are well aligned with new green classifications.

If the Koroyd could be thermally bonded to a skin of similar material to it's core that has been laminated to a fiberglass/Aramid/Kevlar/Carbon-Fiber layer, would it be any better (stronger/lighter) than what's out there?

I would think it depends if energy absorption (impact strength) is favored over stiffness and or other strength measurements.

https://koroyd.com/

What’s Koroyd?

Koroyd is a series of engineered tubes that provide impact absorption. The tubes can be cut, shaped, cnc’d, thermoformed or laminated to be implemented into all sorts of helmets and protection. Endura’s new MT500 helmets join Smith’s helmets with the use of Koroyd.

EDIT: Found more information that might answer my questions.

KOROYD IS AN IDEAL STRUCTURE FOR LIGHTWEIGHT CORE APPLICATIONS INCLUDING STIFF SANDWICH PANELS AND BREATHABLE REINFORCEMENT PANELS
https://koroyd.com/structural/

HELMET SANDWICH

When applied in laminated shell structures, Koroyd increases the rigidity of the shell helping to spread the load of an impact over the internal liner.

As the load is spread, the shell also crushes acting as a first line of defence, reducing the amount of energy transmitted to the inner liner and contributing to an overall reduction in trauma.

NOTE:
I am looking at this material as a possible car shell or hovercraft hull material.

I think that I read someone was using it as a core material for a propeller, not sure where I skimmed that passage though.

EDIT-2:

Lots more info here:
https://koroyd.com/technology/

[kach22i]

MORE random pics...... - Page 4568 - Pelican Parts Forums

[kach22i]

Truck Vortex Generators Pictures to Pin on Pinterest - PinsDaddy



Aerodynamics Research Revolutionizes Truck Design
https://spinoff.nasa.gov/Spinoff2008/t_3.html

Bicyclists, motorcyclists, and even pedestrians feel a push and pull of air as large trucks pass. The larger a vehicle is and the faster it moves, the more air it pushes ahead. For a large truck, this can mean a particularly large surface moving a large quantity of air at a high velocity—its blunt face acting like a fast-moving bulldozer, creating a zone of high pressure. The displaced air must go somewhere, spilling around the cab into swirling vortices. The air traveling along the side moves unevenly, adhering and breaking away, and sometimes dissipating into the surrounding air. At the end of the cab or trailer, the opposite effect of the high-pressure zone at the front develops; the airflow is confronted with an abrupt turn that it cannot negotiate, and a low-pressure zone develops.

The high pressure up front, the turbid air alongside and under the vehicle, and the low pressure at the back all combine to generate considerable aerodynamic drag. A study published in Automotive Engineering in August 1975 found that a tractor trailer unit moving at 55 miles per hour displaced as much as 18 tons of air for every mile traveled. In such cases, roughly half of the truck’s horsepower is needed just to overcome aerodynamic drag.

Airtabs came out of NASA research?

One study conducted in 1989, “Turbulent Flow Separation Control,” explored controlling airflow—flow separation—to decrease energy expenditure and weight in airfoils, inlets, and diffusers and improve aircraft control and decrease drag. The study employed vortex generators, aerodynamic surfaces protruding from a body that draw faster moving air to the surface of the vehicle and disrupt the slower moving boundary layer air around a vehicle, the use of which can be traced back to research conducted by the National Advisory Committee for Aeronautics (NASA’s forebear) in the 1950s. The generated vortices “energize” the slower-moving boundary layer and thereby reduce drag and, in aircraft applications, increase lift.

[kach22i]

Divergent thrust with a perimeter air induction (from what I can tell)...................will it function as claimed?

VENTURI ENGINE*
https://www.hoversurf.com/technology

We came up with a revolutionary Venturi engine and a hybrid aircraft schematic that combines that of a airplane and copter without the transitional regime. These technologies will allow us to see the future today! This unique electric engine is based on the Venturi effect, the meaning of which is the following: the ordinary atmosphere air is injected to the output stream of the engine, creating an additional stream and reducing the noise of the high-speed jet inside the stream. This gives a significant increase in engine efficiency and noise reduction. Our patented engine are 2 times smaller and much safer while having the same thrust as a propeller, this is because all rotating mechanisms are hidden inside the body.

*patented

I'm assuming an axial fan driven by an electric motor.

[Piotrsko]

I fail to see how they have the same thrust as a long aspect rato prop that uses the same input power.

I also don't understand what the patent is about. ROHR was doing similar things 25 years ago