Friday, February 13, 2009

The Arcturus CamperCycle Project

Finally after five years of planning and three trial attempts at a frame, The Arcturus CamperCycle is ready to be built. The new version will be a three wheeled vehicle with two wheels up front and one in the back so that it can take on a teardrop shape with maximum aerodynamics. Being a trike also makes it legal as an electric assisted bicycle so there will be no problem driving it on the street. Make no mistake, this is a full sized motor home, not a coffin on wheels, so it will sleep two or more people comfortably and have the same size interior and amenities that any small motor home would have. Before I dig into the technical details, have a look at this huge pile of notebooks from the past few years that have included many of the design incantations of Arcturus.

Original concepts had a side by side tandem tadpole trike pulling a large trailer unit, and I went as far as building the actual trike before realizing that the weight of the trailer would require a more robust and electric assisted trike to pull it। The truck and trailer idea was scrapped is it just did not seem as cool as an all in one motor home style unit that you could just pedal onto a campground and park. Another version was tried by extending the frame of our KyotoCruiser sociable delta trike by 10 feet in order to build a camper area in the back.

Although the base vehicle did work very well, it became clear that suspension was needed on all wheels and something more robust than bicycle wheels would be needed in order to carry the entire weight plus deliver the powerful electric assist to the road. Another version of the delta frame was built using 2 inch square tubing and was designed to use 16 inch trailer wheels and brakes. Again, the design become complex because of steering and transmission issues between the human input and electric power, so a completely new design was needed. Bored one night, I dug through five years of notes to realize that a very early concept was probably the best all around - one that used a Jeep front differential of all things.

You might think a Jeep differential would be overkill for a human/electric hybrid vehicle, but the design is actually perfect. A "Dana-30" differential only weighs about 150 pounds and includes a front wheel drive system with included Ackerman and center point steering, disc brakes on both sides, and a perfect gear reduction system to connect directly to the PMG-132 electric motor I plan to use. By adapting the battery pack directly to the differential, it also carries 75% of the vehicle weight on wheels that were designed for the task, so in reality, the rest of the camper can be made of lightweight high tech composites. The Jeep differential, motor, controller, and all batteries will be a single "power unit" ready to drive, brake, and steer the entire vehicle. As for human input, I plan to have each rider pedal a single home built axial flux generator so that power will be fed directly into the drive bank with very little loss. When parked, the human powered generator can be used to "top up" the battery banks for all night LED lighting when power is scarce. Roof mounted solar cells will also aid in charging the banks when the camper is parked.

With the PMG-132 motor running from one of two onboard 48 volt packs, the range of the vehicle will be about 100 kilometers at speeds legal for an electric assist bicycle. Having two battery banks makes more sense as the efficiency of the motor is almost 95% at 48 volts, and a large shunt switch can swap banks to keep them from running too low. Since all of the transmission and drive system is all self contained at the front with the differential, a simple motorcycle swing arm and suspension will be used at the rear of the vehicle.

That's all for now। As soon as the snow melts and I can source a Jeep Dana-30 differential, I will begin working on Arcturus and documenting every single step. I think a full sized human/electric motor home with a range of 100 kilometers is just what the world needs as gas prices skyrocket out of control and waist lines bulge! I also look forward to hearing from the many talented garage hackers out there as this project progresses, so please drop in and say hello!