Recent content by spork

Yup. The whole idea that we built a wind powered cart that could simply go faster than the wind makes it sound even more pointless than it was.

We'd be happy to have someone do a documentary on the project. Just a slight correction... We tried like crazy to get Mythbusters to take on the myth that you can't make a wind powered vehicle go downwind faster than the wind. We never entertained ideas of getting our ugly mugs on...

I certainly didn't think it up (and it turns out I was not the first to think it up in any case) for any practical value. But it turns out that it could potentially have a good deal of practical value. You can harvest a great deal more wind energy with a moving propeller or turbine than you...

Agreed. I've used that and similar examples many times. I encourage people to grab a spoke on their bike below the hub and push it forward - or pull a yo-yo along a table with the string exiting below the hub. I fear that you drastically underestimate the challenge of convincing those that...

Yes, JB and I initially did refer to it as "advance ratio". I think this would be the ideal term if not for the fact that it's too easily confused with the advance ratio of a propeller.

The vehicle has a "design speed" given by the turbine pitch and gearing. This is what we call the "vehicle speed ratio" (VSR). It's the rate at which the turbine would advance through the air divided by the rate at which the wheels advance over the ground - keeping in mind the two are...

This is true as well - and is true of both the upwind and downwind cart. In fact this is how I originally conceived of the downwind cart (though it turns out I was not the first to do so). To understand that the blades are on a continuous helical tack, it's of course important to understand...

Absolutely right. It's also worth mentioning that, while there's a sort of change in operation mode for the downwind cart, the change is not fundamental. For the downwind cart, the wheels turn the propeller - always - at all speeds both above and below wind speed. For the upwind cart, the...

Some questions were posed via PM that I'd like to respond to on the thread (I've already responded by PM as well)... That's essentially correct. It's basically a couple of wings swung around an axis. The lift generated pulls the vehicle forward. That's correct. There is a fixed ratio...

If you build one you definitely have to let us know how it goes. You too can play a part in the grand hoax. :)

Andy Ruina and I have become friendly acquaintances over the last couple of years. Interestingly, he's done some really good work on another topic that I've debated hotly on internet forums - namely bicycle dynamics (and particularly the need to counter-steer at all speeds). He's a very very...

That's why we documented everything about the project to the best of our ability and posted it in our build blog. We also set a record - not because we wanted a record, but because it would necessarily involve a trusted and disinterested 3rd party scrutinizing our efforts. Finally, I posted...

Some raw video from the runs. It looks like we'll be submitting data for a run at 2.1X wind speed directly upwind. http://www.metacafe.com/watch/8679238/blackbird_going_directly_upwind_faster_than_the_wind/

Correct. But there is something else - there is the coordinate system in which you're measuring all velocities. You talk about the planet slowing down and the satellite speeding up. So you're clearly not using either of them as the basis of your coordinate system. You're presumably using...