With a bit more research into availability and price, we should be able to settle on a line to use in our test mule. 
Bob, in spite of all the various demands on his time has generously jumped in with both feet to help us ensure the success of this relatively small (by comparison) project. His knowledge is invaluable in all areas of the venture, but he is particularly focusing on idealizing a prop design and also consulting on the transmission components. The transmission of the Daedalus was his primary responsibility and thus he brings a load of experience in lightweight and efficient transfer of power to the project. We are very fortunate to have him involved.
Here's a shot of the twisted belt drive from one of our older carts. The side that is under tension during operation is on the right. We line that side up as well as we can and let the loose side do most of the angling on the pulley. There is still a lot of drag caused on each end though with the belt rubbing.
Rick and I (JB) drove up to what used to be the Alameda Naval Air Station near Oakland today. We wanted to look at the old runways hoping for a suitable test area for the DWV (Downwind vehicle). Above is an aerial from Google with a red line in the suitable test area.
The team would like to use a three wheeled vehicle for ease of steering setup (two fixed spindles and one steering spindle). The question became 'steering spindle' in the front of the vehicle or the back?' Considering that the prop has been placed in the rear, it seems safety again drives the location of the two fixed spindles.
With the mass and height of the prop creating a rather high CG at the aft end of the craft, it's determined that the two wheels should be at the rear and have a rather wide track for the sake of stability. A solid (but breakable) axle will connect the two rear wheels and be used to drive the prop.
Radio control options involve carrying batteries onboard the vehicle. While it can be effectively argued that this stored energy isn't being used to move the vehicle, just the mere existence of the batteries on the vehicle does open up a door to arguments the doubters would likely use. Vehicle will thus need to be steered through a track mechanism or carry a pilot.
It was determined that the best option was a vehicle similar in size to Dr. Bauer's with a pilot on board would provide the most flexible platform.
The first Team meeting was held mid-September 2009. General design, manufacturing and testing considerations were discussed.
Tentative and rough design criteria follows:
Steve received a B.S.M.E. from Bucknell University in 1983, an M.S.A.E. from Stanford in 1984, and a Ph.D. in Aeronautical and Astronautical Engineering from Stanford in 1990. He currently serves as President of the MLB Company in Palo Alto, CA - a company that produces miniature unmanned aircraft for commercial use and flight control systems for remotely piloted aircraft. MLB Company has developed surveillance aircraft ranging in size from 6 inches to 6 feet, many of which operate autonomously.
He built and tested his device on a residential street near his house and taped the test while riding his bike and steering the model cart via radio control. Jack was more than satisfied with the results as were his friends who trusted his testing methods.
A friend of Jack's posted the video on YouTube for fun and all hell broke loose. Jack was accused of all manner of shenanigans -- some said he was having the cart towing with a fishing line during filming, others said he was running the cart on downhill street, hiding batteries and motors, placing the air indicator in a misleading location, powering it through stored gust energy, running the cart at a significant angle to the wind, weaving it back and forth to propel it like a skater, etc, etc.
Did Jack cheat? There will never be a way to know for sure, but this team intends to answer the question 'did he need to cheat' once and for all.
Rick Cavallaro has sailed for over 30 years, and was well aware that sailboats could tack upwind, run directly downwind, and go significantly faster than the wind when sailing across the wind. He got to wondering whether it would be theoretically possible for a sailboat to sail downwind at an angle such that the boat's direct downwind progress would be greater than the wind speed. He did some basic vector arithmetic based on the concepts used in sailing and found that indeed it should be possible to do exactly this, given a boat of sufficiently high performance.
With just a bit of research Rick learned that ice-boats and land-yachts do this routinely. He realized this meant one could release a balloon and race it downwind by tacking downwind in a land-yacht - and the land yacht would win the race quite handily. Given his love for brain-teasers, and this new knowledge of something that seemed somewhat counterintuitive, he wondered if it would be possible to design a vehicle that could use the same principle to go DIRECTLY downwind faster than the wind. With a bit of thought it occurred that one could reproduce the aerodynamics and physical constraints of the land-yacht by simply having the sail follow a continuous downwind tack, but wind that tack into a spiral. Two such sails would simply form a propeller. By gearing this propeller to a set of wheels, you could constrain it to follow the same downwind path that the sail of the land-yacht follows on a steady downwind tack. So it seemed such a vehicle could in theory be constructed quite simply.
Sometime around 2004, Rick posted this brainteaser on an internet forum expecting to get some right answers, some wrong answers, and a few exclamations of "wow - that's pretty cool". What he got however was surprising. This problem raised a stink that ran across 1000's of pages over countless internet forums. Many people (including some aero and physics PhD's and professors) were absolutely certain it could not be done. Many were extremely insulting of Rick's intelligence and sanity.
In the course of these forum threads, it came out that Andrew Bauer had built such a vehicle in the 1960's - and it was designed to carry a driver. Unfortunately, there was no concrete evidence as to whether it had succeeded in its mission. Eventually, JB joined in on the fun, and convinced Rick that the skeptics would never be won over by Rick's analyses and analogies alone. JB was sure that the only way to convince the skeptics was to build a working model. Surely, if they saw compelling video evidence, it should quickly put the matter to rest.
So Rick and JB locked themselves in the Sportvision lab one rainy weekend and built such a model. Initial results with the model were marginal at best - but the effect was amazing. Within 2 days of posting the video on the internet, one of the greatest skeptics built his own version of the downwind cart. But his version was small and slick, and performed GREAT. In the true tradition of science, Rick and JB took that design, made slight improvements, and ran with it. The result - even greater controversy on the internet forums.
The project this group is now undertaking is to build a full scale model that will run outdoors and carry a driver, while witnessed by the public, is intended to put the matter to rest once and for all. No matter the outcome, we're reasonably certain it will not satisfy the most ardent of skeptics.
