The Arcturus Hybrid Camper Cycle Project History
The original Kyoto Cruiser Sociable Trike
| Since the day I began dreaming up bicycle creations, I have always wanted to create a large human powered camper with an electric assist running on batteries that are self charged using solar power. This vehicle would have to be large enough to sleep at least two people and have enough room inside to stand up and move around. Of course, the entire unit would have to be made extremely light for its size and incorporate space age design and materials in order to remain partly human powered. With the new power assisted bicycle law, I could now add a 500 watt motor to the camper as well, so this would make hill climbing a lot easier, and allow for a larger battery bank that would run the motor for at least 50 KM and then power all of the onboard electronics and appliances when parked. The vehicle also had to have no more than three wheels, or it would not legally be classified as a bicycle in my area, so the trike design was the only option and would allow for a more streamlined body. |
The inside of the camper area will be 4 feet wide, 10 feet long, and 6 feet tall. The cockpit area of the camper will have a bout the same size as the Kyoto Cruiser shown above, with plenty of room for two riders to sit comfortably without rubbing arms or shoulders. Of course, there will be a main seating area that also pulls out for an additional 2 person bed, a large table, storage area, small sink, stove, heater, and built in LCD screen, all running off the battery bank. The battery will self charge using a large solar array mounted on the roof of the camper and via plug-in during cloudy days or between long hilly journeys. This may sound like a lot of equipment, but I plan on a total weight of no more than 400 pounds. 400 pounds is 200 pounds of cycle per person, and if you include the power of the electric assist motor, pedaling the vehicle will be as easy as riding any bicycle. Regenerative braking will also be incorporated into the custom computer controlled charging system, motor controller and "smart" assist system, which will instinctively know how much power to split between human and motor for seamless hill climbing and acceleration.
Initially, I tried to convert the Kyoto Cruiser (shown above) tandem trike into the base vehicle for this camper since it already had three wheels, sociable seating and a rugged frame. The resulting frame modifications are shown below before any trussing was added to the frame to make it stiffer.
Modified Kyoto Cruise test vehicle
| Although the Kyoto modifications were very successful, I decided not to continue this version and opted for a fully redesigned trike with all wheel suspension, two wheels in front and a larger wall tube frame. A trike with two front wheels will allow a more aerodynamic body to be made so top cruising speed and distance can be increased. Contrary to popular beliefs, a fish shape is much more aerodynamic than a wedge shape with the pointed end facing forward. This new design will also yield a larger cockpit windshield for driving safety, and will allow the motor and battery bank to be placed at the rear of the vehicle for better drive wheel traction. I have also decided to increase the main frame tubing to 2 inch square with a 1/16 inch wall to make a very light yet stiff frame. |
May 2, 2007
With the new stiffer frame and full suspension, larger batteries and a 2000 watt assist motor can be used, but bicycle wheels would become the weak link under that type of loading. For this reason, the wheels used will be light duty trailer wheels, which weigh only twice that of 24 spoke BMX wheels yet offer a safe load carrying capacity of almost 6 times as much. I will be using bicycle disc brakes on the two front wheels and a motorcycle disc at the rear wheel, which will also be the drive wheel. Each rider will have an independently shifted 15 speed transmission which will combine through a jackshaft to the rear wheel.
Arcturus basic size and shape
|This CAD render shows the overall size of the camper and frame and will be used as a guide to build the basic frame. Doors, windows, heating and interior will be designed around the frame, so the above render is just a crude example of basic shape. The goal is to create a rolling frame that can be motivated under human power before working on any electrical system or the body so all the bugs can be worked out easily. From this point on, my only rigid plan relates to the size of the basic frame as shown in the photo below.|
Laying out the basic frame
| May 8, 2007 |
Here are the 8 tubes that create the perimeter of the basic frame. These tubes are 2 inch square with a 1/16 inch wall, so they are very light and quite stiff. There is almost no flex in the 10 foot long tube if I stand in the center while each end is supported by the buckets, but I will still be adding trusses to carry the increased load of the body and electrical system. On an unfaired mono boom vehicle like the original Kyoto Cruiser, a little frame flex is not only considered, but it is a practical suspension system for light road shock. On a faired vehicle though, the frame must also support the body work, which could crack or become damaged if the frame were to flex, which is why I will be adding trusses to increase the frame stiffness many times over.
The camper body will actually be made as a separate entity and then placed on top the frame much like the way many RV's are constructed so it will not rely solely on the frame for integrity.
Part of the main frame completed
| May 9, 2007 |
Using my 3D render as a guide, I cut the tubing for the main frame and tacked it all together. All tubing is mild steel square tubing with a 1/16 inch wall. The main boom is made from 2 inch tubing, the bottom trusses are 1 inch, and the tubes that form the triangles in the trusses are 3/4 inch. Even tack welded, the frame is extremely stiff and there is no detectable flex with two adults standing in the middle with each end supported as shown in the above photo. The other surprise was the weight of the frame at this point - much lighter than I thought it would be. Once the main frame is complete, it will go on the scale for a weight check.
The frame is just over 15 feet long right now, but once the body and rear swing arm is in place the vehicle should end up just over 18 feet in total length, which is perfect. The two front wheels are positioned at the passengers seating area, so the wheelbase will be just over 10 feet and will allow a turning circle much better than many compact cars, although I doubt Arcturus will see to many tight spots such as a bike path.
Nomad trike with generator drive
| May 14, 2007 |
Shown above is the generator drive system from an old prototype single passenger sleeper trike called The Nomad. Although the gear reduced DC motor was only 75% efficient, it did provide many options for a chainless hybrid drive system, allowing the generator to input drive power, charge batteries, and made it easy to seamlessly integrate human and electric power to a single rear drive motor. I have decided to give Arcturus a similar drive system, but this time I will be building from scratch my own custom low RPM high efficiency axial flux generator using NIB magnets. This generator will be in the 90+ efficiency zone, and not require any lossy gear reduction, so the entire hybrid drive system including controller electronics should be very efficient and smooth. This system also eliminates much excess chain and a few of the bicycle freehubs that would be needed. Each rider will still have their own 15 speed transmission into a shared axial flux generator shaft though, so effort can be tailored to personal preference for cadence and torque. The rear suspension swing arm will be the next step.
Rear suspension swingarm parts
|The rear swingarm tubing will be made from 1/8 inch wall 1.5 inch square tubing. This tubing is the perfect width to mount the rear wheel pillow block bearings to and has twice the wall thickness of the main frame tubing due to the fact that it will also carry the main drive motor. The two bearing tubes each contain a pair of 3/4 ID sealed bearings so that the suspension movement will be very smooth and friction free. The bearing tubes will be welded to the end of the swingarm tubes and held to the main frame by a bolt on each side.|
Swingarm and bearing tubes welded
|The basic swingarm is now completed, ready to have the holes drilled for the two 3/4 pillow block bearings that will carry the rear wheel, main drive sprocket and motorcycle disc brake. The swingarm will also carry the main drive motor so that its mass will be placed over the swingarm mounting bearings to keep shock to the motor down to a minimum. A single gas filled mono shock design will most likely be used for the rear suspension, much like a motocross bike, which will allow good adjustability and a lot of travel. The next step will be the installation of the rear wheel bearings, drive axel and swingarm mounting brackets.|
End caps and rear wheel bearings
|The pillow block bearings will carry the 3/4 rear drive shaft, rear wheel, drive sprocket and disc brake. End caps have also been added to the ends of the swingarm tubing to keep out moisture and prevent the walls from collapsing as the bearing bolts are tightened. The pillow block bearings will be on the underside of the swingarm so the bearing is pressed up against the swingarm tubing, keeping most of the stress off the cast iron bearing body.|
Swingarm mounting brackets
| May 22, 2007 |
Using my favorite tool, the angle grinder, I cut these swingarm brackets from some 1/4 inch angle iron. They will carry the two rear swingarm bearings after being fastened to the rear of the frame.
Swingarm brackets and bolt
|Each of the two swingarm bearings will be held between a pair of mounting brackets by a 3/4 inch bolt and locknut. These heavy duty swingarm mounting brackets will take the stress away from the rear of the frame and spread it out into the walls of the tubing.|