SOHH: Solar human hybrid transport for the whole family (and the dog)
By Paul Ridden
June 19, 2009
If the words "human hybrid" conjure terrifying images of Christian Bale battling it out against Skynet and a league of Terminators then the Solar Human Hybrid Project (SOHH for short) might come as a bit of light relief. It's a one of a kind. It's a great-looking 4 wheeler where the power comes courtesy of the harmonization of solar power and a good old-fashioned lower body workout. There's an iPod dock, a GPS navigation system, a cargo area and even a platform especially for the dog. It's definitely a worthy contender for the crown of coolest green transportation around. Oh, and it's also a school project.
A cunning plan
A search for other articles on this vehicle will yield information claiming this project was the work of a class of 8th graders. It was in fact the sole work of David Dixon (the 8th grader) and his father/mentor (also called David and not an 8th grader) for a Novato Charter School project looking into alternative energy sources and green transport solutions. Young David produced a design plan and presented the outline for the SOHH project to his teacher in August of 2008. He wanted to produce a human/electric vehicle to replace trips to school by car - he would ensure that the craft was street legal, that it wasn't too big for use in cycle lanes, that it would use solar power and that it would have room onboard for the groceries.
Everything set, the Davids set about locating parts, refining design elements and testing theories. One of the first project decisions was whether they should build the vehicle's chassis themselves or try and locate one ready built. The answer came to them in the shape of the Zero Emission Machine (ZEM) 4cycle.
The Swiss-made quadricycle met all of the project requirements and more. At 2.72 meters in length, 1.17 meters wide and 1.04 meters high it was roomy enough for ample modification and small enough to fit in a standard cycle lane. It benefited from a light but strong aluminum frame and offered a smooth, comfortable ride for the whole workforce (everyone being able to pedal at their own pace thanks to independent 7 speed gear controls). Perfect!
There was only one problem - production of 4cycles had ceased several years previously due to high production costs. Luckily, prayers were answered in the shape of a Maryland dealer who had snapped up the last 3 models when ZEM went bust. The Dixons said goodbye to $4600 and said hello to a pristine, shrink-wrapped beauty.
After spending a bit of time getting to know the newest addition to the family, work then began on making it a viable alternative to the car for school trips. California State law dictates that an electric vehicle of this type should be limited to 750 watt (1 horsepower) and not exceed 20mph so the project target was to have their monster reach a maximum of 18mph with 2800rpm. After some trial and error, they settled on a Scott 1hp 24 Volt high efficiency permanent magnet motor which knocks out 3000rpm and is specifically designed for use in electric vehicles.
The shopping list
All those years living on a sailboat gave the Davids enough know-how and enough confidence to design the schematic for the electrics themselves. After which they spent the next few months researching and locating the rest of the parts needed to turn the design dream into a green-powered reality.
The shopping list ended up looking something like this:
Finally, after extended periods of building, testing, reshaping, more testing, modification, yet more testing, remodeling, and testing again - the flame red phoenix was ready to rise.
The final incarnation relies on passenger pedal power and solar charged battery power to drive it. The panels themselves don't directly provide the electric assist, mentor David explains, "The solar panels charge the batteries which run the motor. The panels help power the motor during use in the sun, but the motor requires more amps than the panels can put out. We looked at being able to capture energy while moving (regeneration) but the drag when pedaling would be greater than benefit of generating electricity, storing it and than running it back through a motor. Even just limiting the regen to breaking would give us minimal advantage because of the relatively slow speed compared to a car."
The Samlex converter in turn leeches some of this power to run the iPod dock and the headlights. Independent gears for each rider ensure a pleasant experience for all who travel in her. The Garmin GPS tells you exactly how to get to where you want to go. And yes, there's even room for the dog!
In March 2009 young David gave a very successful project presentation to a high school Physics class and a few days later was made an honorary member of Sustainable Novato after showing off the SOHH to the Board.
Project aims in the bag, time to relax right? Not for this family, their creation made its world premiere at the Bay Area Maker Faire just this month, which has been followed by extensive media coverage.
Where can I get one?
Unless you build your own, you can't. The project - including schematics, parts list and build details - has been documented by young David on the SOHH website, take a look.
The Dixons are certainly not the first to create their own solar power/electric/human hybrid vehicle (the first one I can remember seeing was the solar gondola and even that wasn't the first) but given that the SOHH was created to meet an 8th grade school project requirement and it was built by a family as the labor of love it obviously is, it will hopefully serve as inspiration for many more zero emission designs to come.