DDWFTTW Circular Wind Tunnel Test

[rcgldr]

"continous" video

OmCheeto, did I miss your epiphany on DDWFTTW? If so, what was your turning point?

It's my guess is that the "continuous" video demonstrates that when traveling DDWFTTW, that since the ground speed is faster than the air speed relative to a DDWFTTW device, it allows DDWFTTW devices to to effectively gear down the faster ground speed to the slower air speed, with the leverage effect of the gearing increasing the force at the air interface (but at a slower speed).

 

[OmCheeto]

OmCheeto, did I miss your epiphany on DDWFTTW?

No. But that doesn't mean I don't like watching people build these devices. They are always great fun to watch and make my brain hurt trying to understand their operation. I look forward to the test of the SJSU machine. It is a beautiful piece of engineering.

 

[mender]

They're doing an impressive job, aren't they!

So you're saying you're not quite there yet? I lean heavily on physical evidence then take a while to fill in the blanks. Maybe I covered some of the ground you're on and can help?

 

[OmCheeto]

They're doing an impressive job, aren't they!

So you're saying you're not quite there yet? I lean heavily on physical evidence then take a while to fill in the blanks. Maybe I covered some of the ground you're on and can help?

Great!

Describe the effect with only equations.

ie. no words, graphs, pictures, nor pseudo-vector diagrams are allowed.

 

[rcgldr]

Describe the effect with only equations.

wind_speed_wrt_ground = +10 mph
ddwfttw_cart_speed_wrt_ground = +15 mph

ground_speed_to_effective_thrust_speed_gear_ratio = .5
wind_speed_wrt_ddwfttw_cart = -5 mph
ground_speed_wrt_ddwfttw_cart = -15 mph
effective_prop_thrust_speed_wrt_ddwfttw_cart = -15 mph x .5 = -7.5 mph
ground_force_required_to_drive_prop = -1 lb
effective_prop_thrust = +1.5 lb
drag_plus_rolling_resistance = -.5 lb

net_force = -1 lb + 1.5 lb - .5 lb = 0 lb
net_acceleration = 0 mph / second

power_input = 15 mph x 1 lb = .04 horsepower
power_output = 7.5 mph x 1.5 lb = .03 horsepower
losses_in_power_conversion = .01 horsepower

 

[mender]

Great!

Describe the effect with only equations.

ie. no words, graphs, pictures, nor pseudo-vector diagrams are allowed.

How about in Norske?

Thanks, Jeff! So OmCheeto, all is good now?

 

[mender]

And was that you over on the other forum?

 

[OmCheeto]

How about in Norske?

So OmCheeto, all is good now?

Only one thing comes to mind:

Gentlemen, congratulations. You're everything we've come to expect from years of public education.

shamelessly stolen from http://www.angelfire.com/oh/quotations/movies/m/meninblack.html" .

 

[mender]

Likewise, I'm sure!

"Then I saw little Tiffany. I'm thinking, y'know, eight-year-old white girl, middle of the ghetto, bunch of monsters, this time of night with quantum physics books? She about to start some ****, Zed. She's about eight years old, those books are WAY too advanced for her. If you ask me, I'd say she's up to something. And to be honest, I'd appreciate it if you eased up off my back about it."

 

[A.T.]

Spork & JB finally tested their cart in natural wind:



http://www.youtube.com/watch?v=aDzWh9J1dk4#t=1m23s

Their blog:

http://www.fasterthanthewind.org/

 

[rcgldr]

Very impressive results. In the meantime I found a youtube video of some sort of "upwind" cart competition.



Spork and JB should be able to acomplish the same thing by increasing the pitch of the prop enough that prop pitch speed (prop_pitch x (revolutions / second)) > ground speed, perhaps starting off with prop pitch speed at 3x to 4x ground speed. In this case the prop would be acting at a turbine driving the wheels (as opposed to DDWFTTW mode, where the wheels drive the prop).

 

[A.T.]

In the meantime I found a youtube video of some sort of "upwind" cart competition.



Spork and JB should be able to acomplish the same thing by increasing the pitch of the prop enough that prop pitch speed (prop_pitch x (revolutions / second)) > ground speed, perhaps starting off with prop pitch speed at 3x to 4x ground speed. In this case the prop would be acting at a turbine driving the wheels (as opposed to DDWFTTW mode, where the wheels drive the prop).

I think they have some limits on turbine size in the upwind races. Here is a lecture by one of the participants (or even organizers) of those races:
http://www.youtube.com/view_play_list?p=6C046C08399626CA

Here is an animation that shows the symmetry between directly upwind & directly downwind faster than wind:

 

[rcgldr]

I think they have some limits on turbine size in the upwind races. Here is a lecture by one of the participants (or even organizers) of those races:
http://www.youtube.com/view_play_list?p=6C046C08399626CA

It also appears that the upwind carts are allowed to use clutches as the turbines are moving when the carts are not. This allows for faster launches.

For DDTFTTW carts, a variable pitch prop would help with launches, since ground to prop pitch (thrust) speed can be any value below 1 (including negative ratios, < 0 is just slower than wind speed) but there would be some additional losses due to whatever mechanism was used to control prop pitch, unless it was something similar to a torsion spring controlling the pitch based on the amount of thrust being generated, and it's an uneeded complication as you could just give the carts an initial push if the goal was to achieve a top speed.