The Old Bike
The Old Bike is the current test platform of the Cornell Autonomous Bicycle Team. It is a converted folding bicycle developed by Andy Ruina's lab.
Mechanical Components
Front Motor Assembly wip.
The assembly sitting on the front of the bike is one of the main components of the bike. The assembly steers the bicycle by turning the front wheel, much like a human. However, instead of using handlebars to apply a moment to the stem, the assembly is directly attached to the fork. The motor notably must be in line with the axis of the wheel.
The current motor enclosure was created by welding a circular steel plate to the intersection of the head tube, top tube, and down tube. This acts effectively as a base for the entire assembly. The welded plate supports all of the weight of the assembly as well as any produced torque. The leveling of the head tube, from the inclusion of the steel base, allows for direct access to the fork. In lieu of a stem, a rod was placed inside of the exposed fork and bolted at its end to prevent rotation. The insert is threaded on its bottom end to interface with the fork, and is connected to a coupling at its top. This coupling connects with the drive shaft of the motor. This allows for the power from the motor to be translated down to the fork and effectively control the bike's direction.
The motor is a large 24V, 80W motor found in Andy Ruina's lab. The motor speed is then stepped down by a 3:1 gearbox to increase torque and decrease speed. There are plans to replace this motor, as it has been described as "jerky". The backup motor awaiting testing is a VEX Robotics BAG Motor stepped down with a 36:1 gearbox. The lessened power and increased gearing will allow any motor coasting to affect the steering inconsequentially as well as create more reliable, precise movement of the front wheel.
The surrounding components of this assembly are also important. An orthogonal plate is placed directly above the original base plate to correct any offset from the fork caused by the placement of the steel base. This plate is connected directly to the base plate with nuts and bolts. Proceeding this is a plate that was added to stabilize the encoder, and two more were added to constrain the motor. Between these plates, four long threaded steel rods and an assortment of nuts were used to connect the plates to mesh the system.
