Flywheel Powered Car 3

Objective: Make the car have remote control steering and throttle, the electronic components must be run from the power of the flywheels, and the the run time of the car must be significantly longer

Notable car features: 

• Car has two 8lb flywheels with 35 times the inertia of the second car

• Electric generator creates power for the remote control system so the only stored energy on the car is that of the rotating flywheel. The generator produces 30 volts at operating speed, that electricity is then converted to a stable DC 6 volts and supplied to the receiver

• Steering uses servo and incorporates Akerman geometry for optimal steering

• Transmission has two speeds and an neutral gear that can be controlled through RC remote

• Drill spinning mechanism allows for car to be "charged" in a matter of seconds

• Flywheels counter-rotate to cancel out gyroscopic and angular momentum effects

Challenges Overcame:

Generator voltage requirement: A high output voltage of the generator was required due to the diminishing voltage output as the flywheels slowed. I aimed for roughly 40 volts at max rpm however this was a challenge. Upon initial testing a single coil of the generator was producing roughly 1/4 of the needed voltage so I went back to the design and added more coil windings, reduced the gap between the coils and magnets, and added another rotor to the other side of the coils. This resulted in a 30 volt generator at the new lower operating rpm.

CVT replacement: Original design used a continuously variable transmission (CVT). In theory it was a perfect choice, however in practice it lacked almost every way. It did not transfer enough torque, the control mechanism was too hard to operate, and it could not fully disengage the flywheels to the wheels. Instead of trying to fix all these problems I decided to go with a 2 speed transmission with a design similar to a manual car transmission. It solved all the issues in that is is efficient, reliable, and transmits enough torque. The only drawback is the limited amount of speed choice the drive has.

Steering and tire re-design: When the steering was tested the movement was limited and the servo's plastic gear teeth were slipping. The steering was requiring too much force to turn the wheels. To fix this I redesigned the geometry of the wheel, tie rods, and steering knuckles. I reduced the amount of tire that contacted the ground, used a tire material with less grip, minimized the scrub radius of the wheel, increased the mechanical advantage of the servo with longer knuckle links, and upgraded to a metal gear servo. All of these marginal improvements added up to a working steering system.

Electronics holder: First electronics holder exposed all the electrical components and this lead to durability and neatness issues. Therefore I redesigned the electronics holder to be incased and also hold the servo that controls the transmission.

Flywheel bevel forces: Upon testing of the flywheel spinning mechanism I noticed that the driveshaft flywheel was slipping on the shaft, after a few minutes of use the flywheels would no longer engage the bevel gear. This was solved with an improved metal clamp behind the bevel gear so the high forces would no longer cause slipping.

Below are pictures of the real car.

First Attempt is Below