5
   

I don't understand how this car works.

 
 
spork
 
  1  
Reply Mon 5 Jul, 2010 09:09 am
I don't know when it will be posted, but I know they're waiting for me right now. I handed over the raw data files immediately, and I'm now doing the requested analysis to submit our report to them. My understanding is that they'll go over our data analysis using their raw data files as soon as I do. But I don't know how long that will take. I've already sent them some preliminary results, and expect I'll give them something more polished today. However, I think it's quite likely they'll ask for additional analysis to demonstrate that we've met the requirements of their rules.

The official report for the recent record by Jenkins in the Greenbird was published on the NALSA site:
http://www.nalsa.org/MeasuremantReport/MeasuremantReport.html

It was written by Bob Dill, the same primary observer (and NALSA BOD member) that attended our event. I assume he will write a similar report for our effort and post that on the NALSA site as well.
rosborne979
 
  1  
Reply Mon 5 Jul, 2010 09:24 am
@spork,
I'm going to play devils advocate here for a minute and anticipate some of the challenges to the test procedures...
1. How does NALSA determine that you don't have a hidden power source, like a battery or a spring or pedals or something like that? Do they have independent inspectors check the vehicle just prior to testing?
2. How does NALSA make sure the raw data isn't falsified? Is it kept under lock and key until certified officials get hold of it?
3. Is NALSA certified as an unbiased judge of the tests? Are they considered independent of the results and unable to profit by them in any way?
0 Replies
 
spork
 
  2  
Reply Mon 5 Jul, 2010 10:25 am
>> I'm going to play devils advocate here for a minute and anticipate some of the challenges to the test procedures...

Fair enough.

>>How does NALSA determine that you don't have a hidden power source, like a battery or a spring or pedals or something like that? Do they have independent inspectors check the vehicle just prior to testing?

Bob Dill is extremely familiar with our vehicle at this point. He saw it being built, and watched us assemble it for the runs at El Mirage. I'll be happy to post pictures of what he can easily see - there's nowhere to put a motor.

>> How does NALSA make sure the raw data isn't falsified?

In addition to the two GPS receivers I had on the vehicle, Bob Dill place 3 NALSA GPS receivers on the vehicle. He also placed GPS receivers on the chase vehicles, and on the stationary wind instrument base station. All of his units logged internally. He gave me a copy of that data.

He did not have independent logging wind instruments, but I gave him the raw data from our logging wind instruments before having a chance to do anything to it. Additionally, he had a hand-held impeller style wind meter that he used frequently to check the wind speed before and during our runs. This was done at both the upwind and downwind ends of the course (using a second observer approved by NALSA). They knew what wind we were looking for (ideally about 15 mph) and they gave us the go ahead for each run when the wind was in the right range. Anything less than 10 mph was pointless, and anything over 20 took us over 50 mph and caused transmission failures (e.g. broken chain).

>>Is NALSA certified as an unbiased judge of the tests? Are they considered independent of the results and unable to profit by them in any way?

They're as unbiased as I know how to find. Bob Dill held the wind powered land speed record himself for a number of years. He then went to a good deal of time and expense on his own to follow Richard Jenkins around the globe to certify Jenkins attempt to take Bob's record. Jenkins recently succeeded in doing that (at 126.3 mph). One might think Bob would be biased against Jenkins' attempt. But there is no sense of that at all. Both Bob and Jenkins attended our effort this weekend, and they were clearly friends. We tried to pay for Bob's airfare and hotel simply so he wouldn't be out of pocket ratifying our record attempt. He wouldn't let us. I'd say these guys are as straight up as they come.

To my knowledge, NALSA is the ONLY organization that ratifies wind powered land speed records.
parados
 
  1  
Reply Mon 5 Jul, 2010 10:31 am
@spork,
Gosh spork, the least you could have done was offered to pay for BillRM's trip to view the test. Then we could have all accused him of being paid off.
0 Replies
 
spork
 
  1  
Reply Mon 5 Jul, 2010 10:36 am
>> Gosh spork, the least you could have done was offered to pay for BillRM's trip to view the test. Then we could have all accused him of being paid off.

Sorry - we tried. He wouldn't let us. But even if we succeeded to cover his expenses, it wouldn't begin to cover the week he took off of work to fly out from the east coast and spend his days frying in the desert.

EDIT: D'OH!!! I thought we were talking about Bob. You meant (as you said) BillRM. BillRM was invited to join - just as everyone with an internet connection was invited. We did have a group show up that only learned about this thing a few days ago. Oddly enough they didn't call us names or ask us to pay their expenses. All in all, there was a fairly large contingent of engineers on-hand to witness the event.
0 Replies
 
ThinAirDesigns
 
  1  
Reply Mon 5 Jul, 2010 06:06 pm
Going through the data from the 18 recording sensors that were used for the test it' becoming more and more likely that NALSA has the data to ratify a record of more than 3x the speed of the wind -- perhaps as high as ~3.5x

JB
BillRM
 
  0  
Reply Mon 5 Jul, 2010 10:33 pm
@ThinAirDesigns,
Quote:
Going through the data from the 18 recording sensors that were used for the test it' becoming more and more likely that NALSA has the data to ratify a record of more than 3x the speed of the wind -- perhaps as high as ~3.5x


Amazing still being able to achieved an energy transfer out of an air movement you are somehow leaving behind at 3x speeds.

Now my question is where did you hide the exercise wheel with the ferrets and how many ferrets did it take to power a 3x speeds run?

Perhaps I should report you to PETA.

spork
 
  3  
Reply Tue 6 Jul, 2010 01:05 am
>> Amazing still being able to achieved an energy transfer out of an air movement you are somehow leaving behind at 3x speeds.

That's the great thing about air - you can't really leave it behind when you're immersed in it. That's a bit like trying not to get wet by swimming faster than the current. Just a little bit of understanding of basic phyics could change that "amazement" into simply "interesting".

But I thought you promised to dissappear - what happened?
rosborne979
 
  1  
Reply Tue 6 Jul, 2010 06:08 am
@ThinAirDesigns,
ThinAirDesigns wrote:
Going through the data from the 18 recording sensors that were used for the test it' becoming more and more likely that NALSA has the data to ratify a record of more than 3x the speed of the wind -- perhaps as high as ~3.5x

Is there any reason why the ultimate potential of the vehicle wouldn't be about the same as an ice-boat in tack? I guess I'm wondering how much efficiency is lost in the linkage of the wheel to the prop and in the size and shape of the prop?

You might achieve even better results by changing the pitch on the prop blades as the vehicle picks up speed (like airplanes do), and/or by changing the size of the prop blades.
ThinAirDesigns
 
  1  
Reply Tue 6 Jul, 2010 07:19 am
@rosborne979,
This comparative efficiency question was an interesting surprise to us rosborne. We had always assusumed that for the very reason you surmise (transmission losses) we would be much less efficient than a land-yacht or an ice-boat. Turns out they have there own losses that we don't.

Lets suppose we are in a race to the downwind end of a lake. -Due to the hard connected sail, the other craft must run the chassis the entire time at an angle to the wind. Their apparent wind over this chassis is much higher than the apparent wind over ours, AND it's angle to the chassis makes it very hard to optimize drag reduction. We get a much lower apparent wind and it's perfectly aligned with us.

The Blackbird is already able to compete with the best land sailing craft in the business (including the GreenBird) when it comes to downwind VMG and it was built in a garage with a small budget and it rather rough.

JB
ThinAirDesigns
 
  1  
Reply Tue 6 Jul, 2010 07:21 am
@BillRM,
RillRM: "Amazing still being able to achieved an energy transfer out of an air movement you are somehow leaving behind at 3x speeds."

Your basic mistake in all of this is wrongly asserting that an faster object can't extract energy from a slower object.

Your bad.

JB
Cycloptichorn
 
  1  
Reply Tue 6 Jul, 2010 10:01 am
@ThinAirDesigns,
I think he has a basic misunderstanding of how wind and windstreams work. You don't 'leave behind' wind. It isn't as if you outrun a stream of wind. The odds of being at the absolute leading edge of a windstream are close to zero.

Cycloptichorn
0 Replies
 
rosborne979
 
  1  
Reply Tue 6 Jul, 2010 11:36 am
@ThinAirDesigns,
ThinAirDesigns wrote:
This comparative efficiency question was an interesting surprise to us rosborne. We had always assusumed that for the very reason you surmise (transmission losses) we would be much less efficient than a land-yacht or an ice-boat. Turns out they have there own losses that we don't.

Lets suppose we are in a race to the downwind end of a lake. -Due to the hard connected sail, the other craft must run the chassis the entire time at an angle to the wind. Their apparent wind over this chassis is much higher than the apparent wind over ours, AND it's angle to the chassis makes it very hard to optimize drag reduction. We get a much lower apparent wind and it's perfectly aligned with us.

Is the driver of the vehicle allowed to exert any muscular effort at all? Would changing the prop pitch be considered equivalent to steering (and be allowed)?

Here's why I ask: I'm wondering if you could rig up a lever in the cockpit which allowed the driver to change the pitch of the props as the car accelerated, thus making their impact angle more efficient at whatever speed you are going. If you can get some force feedback through the lever handle the pilot might be able to adjust the pitch by feel, just as an ice-boat pilot can maximize his tack depending on changes in the wind.
Cycloptichorn
 
  1  
Reply Tue 6 Jul, 2010 11:47 am
@rosborne979,
Quote:

Is the driver of the vehicle allowed to exert any muscular effort at all? Would changing the prop pitch be considered equivalent to steering (and be allowed)?
]

Isn't this directly controlled by the speed the wheels are going? If I understand correctly.

Cycloptichorn
rosborne979
 
  1  
Reply Tue 6 Jul, 2010 12:13 pm
@Cycloptichorn,
Cycloptichorn wrote:

Quote:

Is the driver of the vehicle allowed to exert any muscular effort at all? Would changing the prop pitch be considered equivalent to steering (and be allowed)?


Isn't this directly controlled by the speed the wheels are going? If I understand correctly.

The "pitch" of the prop blades is not the same as the speed of "rotation" of the blades.

The "pitch", just as in an airplane, refers to the angle that the prop fins impact the air.

When an airplane is accelerating hard (at takeoff), the prop fins impact the air at a shallow angle, but as the airplane begins to acquire airspeed the "pitch" of the blades can be changed to use the airflow more efficiently.

This is similar to an ice-boat taking a "soft" tack in the beginning just to get moving, and then taking a "harder" tack once some speed has been built up.
Cycloptichorn
 
  1  
Reply Tue 6 Jul, 2010 01:24 pm
@rosborne979,
Would this be achieved by an electric fly-by-wire system? I'm not sure how a lever could change the pitch of a prop that is rotating at high speed. At least, I have no idea how the mechanics of such a system would work.

Cycloptichorn
DrewDad
 
  1  
Reply Tue 6 Jul, 2010 01:47 pm
@Cycloptichorn,
In an airplane propeller, the variable pitch is usually achieved using hydraulics.
0 Replies
 
ThinAirDesigns
 
  1  
Reply Tue 6 Jul, 2010 02:31 pm
As long as the vehicle has a fixed ratio transmission, a variable pitch propeller is allowed by NALSA rules. The fixed ratio transmission precludes storing energy in the prop and then increasing pitch to convert this stored energy into thrust.

During our Ivanpah runs, the vehicle was NOT equipped with a variable pitch propeller, but we converted to such between Ivanpah and El Mirage. The mechanism is a manual linkage (NALSA won't allow use of electrical servos) and you can see how the linkage was constructed in the following links:

http://www.fasterthanthewind.org/2010/05/weve-got-handle-on-it.html

http://www.fasterthanthewind.org/2010/05/things-change.html

http://www.fasterthanthewind.org/2010/05/front-vp-hub-linkage-complete.html

The variable pitch is controlled through a rod running down the inside of the propshaft to the propeller hub.
rosborne979
 
  1  
Reply Tue 6 Jul, 2010 08:31 pm
@ThinAirDesigns,
ThinAirDesigns wrote:
During our Ivanpah runs, the vehicle was NOT equipped with a variable pitch propeller, but we converted to such between Ivanpah and El Mirage. The mechanism is a manual linkage (NALSA won't allow use of electrical servos) and you can see how the linkage was constructed in the following links:

Oh, I see, you've already thought of changing the pitch. In that case, never mind Smile
0 Replies
 
spork
 
  1  
Reply Thu 8 Jul, 2010 09:24 am
WIRED posted an update on our project: http://www.wired.com/autopia/2010/07/downwind-faster-than-the-wind-possible-and-theyll-prove-it/#respond
It sounds like they plan to publish another article when last weekend's record runs become official.
0 Replies
 
 

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