Propeller vs Direct drive

[Superfuelgero]

Off the wall question;
What is the difference in efficiency between propulsion from a propeller vs a direct traction drive (wheels, including drivetrain losses)?

My research lead me to some odd vehicles, and more questions as usual.

[Superfuelgero]

More fun

https://www.youtube.com/watch?v=6j_W...j6Ck6Rs-wXjf36

http://www.dailymotion.com/video/xfn...ler-car_travel

https://www.youtube.com/watch?v=L_CnvRufT7c

Prob fun for its own thread
http://www.techvert.com/wind-powered...than-the-wind/

[Superfuelgero]

True, I'm thinking around 45-70% of direct depending on pitch. Not sure though.
Using
ηp=T∗u/Pshaft

A bad amount for mpg. The project places too much priority on weight though.










Lotus

https://www.youtube.com/watch?v=xRV7RmTk2yA

https://www.youtube.com/watch?v=4LJuGftUFbI

More fun
http://www.treehugger.com/bikes/the-...ith-video.html

[Cobb]

Screw the cars, now an air train, thats front page news. Trains doesnt have much traction, thats why they are soo efficient. They use sand to air in starting off and braking as traction is soo limited due to what little contact all that weight makes with the rails and wheels.

[cRiPpLe_rOoStEr]

I don't see it coming to a mass-production car, maybe a turbine-propelled one would make more sense nowadays.

Originally Posted by Cobb

Screw the cars, now an air train, thats front page news. Trains doesnt have much traction, thats why they are soo efficient. They use sand to air in starting off and braking as traction is soo limited due to what little contact all that weight makes with the rails and wheels.

I wonder if the propeller could even help to improve braking, let's say, if it could be easily reversed in order to act as an aerodynamic brake.

[markweatherill]

Is there any gyroscopic effect?

As for efficiency, I expect it's much less efficient than a direct drive in stop and start driving, and I wonder what it would be like to drive behind a propellor driven vehicle in traffic!

[jakobnev]

With enough back wind a propeller is better.

[Ryland]

From what I remember about propellers, I think it was around 59% energy transfer before it was easier for the air to move around the propeller.

The big advantage is not relying on the wheels for traction, like has been stated, and in the old magazine clippings that is what was stated as well, ideal for low traction areas like mud, grass, ice.

When I've driven an air boat, that is a boat with a flat bottom and a large prop in the back, it was very much a fluid drive, like driving a vehicle with a very loose automatic transmission.

[jamesqf]

It would at least discourage tailgating :-)

[RedDevil]

Then you take your propeller driven car to a restaurant on a sunny warm autumn day.
You find a vacated but narrow parking slot under the trees close to the tables where people dine. It takes some manoevring back and forth to fit nicely in that slot.

You'd better leave a big tip.