Ride the Lightning

Running with the excitement over the last style effort, I decided to neglect the actual mechanics of the bike and continue to make it look pretty.  Pictured here is the new headlight, as well as the new fiberglass "tank", and some freshly stained wooden motorcycle parts.  And being confident with the battery pack design I made a bunch of containers for the battery cells.  Almost everything you see in this picture will be subject to at least one more pass at a better design.

Being somewhat happy with the way the battery/motor setup turned out, I decided to breathe some life into the style of the motorcycle.  As I mentioned before, I wanted to go for the cafe racer style, but with a unique take.  I started with the lowered handlebars and got onto crafting a seat and "gas tank".  I was really excited to finally see things starting to take shape.  Rather than a frame with electronics strapped to it, I felt like I finally had a proper motorcycle.  Later on I used the cardboard mockup as support for laying down some fiberglass, which will act as a cover for the high power electronics that are used for controlling the power to the bike.

Realizing that a floating chain tensioner is going to become unpredictable at higher speeds I opted to redesign the way the motor transfers motion to the rear wheel.  I learned the hard way that the chain driving the rear wheel absolutely has to sit in front of the pivot point of the rear forks, otherwise the chain just becomes loose as the bike moves up and down.  Here I have the motor mount V2, which has a chain running from the motor to a shaft which has its own chain running to the rear wheel.  This was a dramatic improvement over the last design, but it introduced a new problem of how to tension the chain between the motor and shaft.  It was also terribly noisy.  Here I also finalized the placement of the motor controller and tested out the design of the battery pack support.  I was happily surprised at how well the wooden test pieces held up under load.  It gave me hope for when I finally have everything mounted with metal.

Probably the third test ride.  I've still got the ridiculous wooden chain tensioner but I'm finally using the lithium-ion battery packs I built.  Right about now is when I started learning the voltage/current rule:  Voltage directly relates to the speed of the motor, and current directly relates to how fast I can get to that speed.  Since I didn't want to put the batteries in parallel I decided to use the gearing to optimize for the torque I wanted with the batteries wired in series.  This way I always have the torque on demand, and if I want the bike to be faster I just add more batteries in series (increase the voltage).  The side benefit to this is I can configure the bike for city driving with less battery weight and highway driving with more battery weight.  Think of it like a smaller gas tank that reduces the weight of the car when you don't need to travel long distances.

At some point it dawned on me that lead-acid batteries just won't cut it.  From this point on I've been using these battery pack built from scratch using 20 amp-hour lithium-ion cells.  Lithium-ion packs give me the power I need while still being lightweight enough to not feel like I have an overweight passenger riding with me at all times.  To put it into perspective, each of these packs weighs about ten pounds and has as much stored energy as a car battery.  The pack pictured is the very first prototype, using a circuit board fabricated in a PCB CNC machine.  It's also the first time I was scared by what I was making.  See picture for evidence of vaporized wire due to excess electron movement.

I needed to figure out an okay way of supporting the battery packs, so I stole some insulation foam board from my friend's adventure van project to build some sort of spider like battery enclosure.  If you wanted to check out a project full of expert craftsmanship and creative talent I'd point you to his blog if he had one, otherwise you can continue reading mine.