Reflections on the potential of human power for transportation

Saturday, March 31, 2012

Pedaling Along the Skyway

I admit to being a futurist. I have this fascination for the overlap between science fiction and technology. Some of the concepts that fall into this category keep resurfacing, but never become reality. In some cases the timing has not been right. In others the technology is not adequate to make the concept viable. And in some, there are social factors that prevent realization. Take jetpacks or flying cars. How about human-powered monorails? Admittedly, HPMs do not surface as often as the former two concepts, but I have read about at least six systems built before 1900 (see Wilson below), and at least five proposed since 1990. I consider these offshoots of the modern Human Powered Vehicle movement. Is there a system coming to a neighborhood near you?

The people at Google with their 10^100 Prize would have you think so. They have awarded one-million dollars to the makers of a human-powered monorail called Shweeb, the winner in their “Drive Innovation in Public Transportation” category.
We’ll get back to the Shweeb’s practicality after reviewing a bit of HPM history
Prof. David Wilson discusses the pre-1900 HPMs in his article “Transportation Systems Based on HPVs, Past, Present and Perspective”, presented to the “Proceedings of the Fourth International Human Powered Vehicle Scientific Symposium” from August 1992 (parts of which are also in “Bicycle Science” 3rd ed.).
The contemporary interest in HPMs may have begun with a 1990 article in “Bicycle Guide” magazine from June of that year. In that article, entitled “Original Thinking”, seven leading bicycle builders were asked “to tell us about the bike they would build if the prosaic constraints of cost, customer whims and current technology could all be magically lifted.” One of the builders, Gary Fisher ( of mountain  bike fame), responses was “I’d love to see elevated bikeways built like the wooden velodromes, where you’re totally covered in a pipeline that would go in one direction, and you’d have air piped in , in the direction you’re going, so you’d have a perpetual tailwind. Its quiet, its lightweight, and you could elevate it 20, 40, 60 feet in the air to eliminate hills.” The water color painting at the beginning of this post was David Graves’ artistic interpretation of Fisher’s idea.
Jim Kor (of Urbee fame, see the post “Bucky and the Urbee”, below) borrowed heavily on Fisher’s idea with he proposed his Skyway system from 1992. Below are two illustrations from a “Bicycling” magazine article on the Skyway system, from March of 1992, entitled “Cycle City”. In this article the Skyway system has been installed in Seattle using much the same route that is being considered for light-rail. Wouldn’t you know it? The system doesn’t extend far enough North along the Eastside of Lake Washington for me to have easy access to it!

Kor embellishes Fisher’s vision adding specifics like hard rubber tires running in tracks, multiple lanes for vehicles of differing speeds, a double-decker track arrangement  and the suggestion that  the system could support electric vehicles as well. Notice in the Skyway car illustration, the absence of steerable wheels. This would restrict it to very-large-radius curves. Kor does manage to get a lot more press for his concept, including an article in the January 1994 issue of “Popular Mechanics”.

And Bauke Muntz, the talented industrial designer from the Netherlands, proposed a HPM for his Velo Nova HPV theme park in the early 2000s.

Speaking of theme parks, that brings us back to the Shweeb, which has a working prototype in Agroventures theme park in Rotorua, New Zealand.
Before discussing the Shweeb’s transition to public transportation, there is another very Shweeb-like HPM, the Skyride, being championed by Scott Olsen, the inventor of Rollerblades.

While Olsen’s concept of a suspended gondola system may have originated in the mid 1990’s, the building of actual prototypes appears to be relatively recent. The current iteration of the Skyride gondolas can be propelled by rowing as an alternative to pedaling. It is clear that Olsen’s current efforts to commercialize his system are riding the wave from Shweeb’s winning the Google 10^100 Prize.
I am sure there are other HPM concepts I have overlooked, but for the purposes of the subsequent discussion, the Shweeb makes a sufficient point of departure.

The Shweeb is the brainchild of Geoffrey Barnett. The bullet shaped pods are coupled to the overhead rails by a boogie that allows the pod to swing +/-70deg. from side-to-side, like the inverse leaning of a bicycle. The rails are made of an 8” square C-section, and though I don’t have access to the design details, it appears that the drive force comes from a small wheel (less that 8” in dia.) rolling on the inside of the C-section. Pedals are connected to the drive wheel through a seven-speed derailleur system and universal-joint that allows for simultaneous driving and swinging. The installation at Agroventures features two 200m tracks arranged in what appears to be a double-D-oval pattern.
Barnett claims the Shweeb is the most efficient human-powered vehicle on earth and that speeds of in excess of 50mph. are possible. The current speed record for three laps is 58.2 seconds (23mph.) To put this speed in perspective, the world record for running 600m is about 72 seconds, the hour record for an HPV (Varna Tempest) is 56 miles and the flying 200m speed is over 82mph(Varna Tempest again).  Since the pods do have a small cross-section and have an aerodynamic shape, I suspect that the discrepancy between Barnett’s claims and reality is due to the rolling resistance of the small wheels in the track. If the rolling resistance is that substantial, then claims that two pods in tandem will travel faster that one are not valid.
The Shweeb is, in fact, a very expensive version of the bike lane. Granted, being elevated, it can make use of space unavailable to regular bike lanes, but I believe the high cost and very limited user group will prohibit its adoption as a transportation system. I also believe there are two broad changes  
that can be incorporated into a HPM which may bring implementation closer to reality. The ideas I am proposing have been suggested by others, I am only grouping them together as a holistic system.
First, minimize the cost of the system by doing three things. Limit the system to two lanes only, one in each direction. This is simple enough and in keeping with the Shweeb concept for public transportation. Reduce the height of the tracks. Shweeb advocates tracks at 19’ height. Reduce this so the bottom of the system is about 8’ high, enough to safely clear a walking person. An approach for dealing with elevation changes is discussed below. And, most significantly, don’t supply the vehicles. Put all the money into the infrastructure and let the users provide the vehicles. Vehicles could be supplied for rental fee in addition to a system-use fee.
Second, design the lanes so they can be used by multi-modal vehicles. Many communities have transit buses that will carry bicycles, allowing riders to pedal between home and the bus stop and again from the bus stop to the destination. So design the HPM cars so they can be ridden on the street from home to the nearest skyway access node. Kor suggested four-wheel cars with hard rubber (urethane?) tires that  
would run in metal tracks. Provide adequate suspension so the ride on roads is acceptable and keep the spacing between the wheels the same so they can share the same track.
 Miles Kingsbury’s Quattro with a bigger trunk?

Since there is only one lane in each direction, there is the problem of slower cars being over taken by faster cars. This can be prevented by regulating car speed and keeping it the same for all vehicles. As each car enters the skyway from the street an electrically-motorized tow-hook engages the vehicle. The tow-hook, or traction rabbit (see Wilson in Proceedings above), runs between the tracks below the vehicle and accelerates the car up to a speed that is slightly faster that a very-fit rider can propel it. The rabbit has force measuring sensors within it that monitor how much force is needed to pull the car along. If the rider chooses not to pedal then, in effect, his car becomes a purely electric vehicle and the user fee reflects that fact. If the rider chooses to pedal, the force sensor records the reduction in required force, and the user fee is reduced up until the level where the rabbit is only limiting the car speed but the rider is providing all the propulsive energy. The rabbit also can provide extra propulsive force to overcome inclines so the tracks can follow the landscape instead of being high enough to pass over all obstacles and remain nearly horizontal.
The cars could be purely electric, with no provision for pedaling. The rider could use the onboard battery energy to get to the skyway, use the rabbit for the skyway transit to conserve battery energy and use the batteries again to go from the skyway to the destination.
The multi-use skyway cars and the multi-use skyway would maximize ridership and make what could have only been an expensive bikeway into environmental friendly commuter system.

No comments:

Post a Comment