Finished Go-Kart

Success! Fernando and I have finally finished our go-kart. After finishing the mechanical aspects of the car, we worked on hooking up all the electric components. 

First we bolted our throttle pedal to the frame and ran the ground, 5V, and signal wires under the frame to the back where they split to each motor controller. 

We configured our batteries by wiring two pairs of 12V batteries in series and then wiring the two pairs in parallel. This way, each controller can draw up to 24V and 40A because each battery has a 40A fuse. There are two dean connector switches in between the battery configuration and the motor controllers. The switch in the rear can be unplugged and replaced with a battery charger. 

The switch toward the front to the vehicle is the power cutoff switch. Unplugging it will cut all power to the controllers and motors in case of emergency. It is easily accessible from the driver seat or the outside of the car. A large resister and small toggle switch are connected in parallel to the main power switch so that the capacitors in the controllers can be charged before the battery voltage is applied to them. 

We bolted our motor controllers to the back of the car seat.

 Each controller supplies power to the corresponding motor through 3 wires. To determine what current to apply to each of the three motor power cables, a hall sensor board is mounted above each motor as shown below. The hall sensor takes 5V from the controller and outputs a signal on three wires, A, B, and C. Both the motor wires and the hall sensor output wire are connected with bullet joint so they can be swapped out to find the combination that works for driving the motor. 

After we wired everything up, found the correct combination of hall sensor and motor wires, and calibrated the hall sensors, we were good to go. The car works awesome and is so much fun to drive around! Woohoo!!

Rolling Frame

Finally! We are finished with the mechanical side of our go-kart. After spending virtually every waking hour in the shop this last week, we have a rolling go kart with steering, braking, mounted motors, and seating.

We designed the geometry for our Ackerman steering linkage in a 3D sketch in SolidWorks. We then used the dimensions from the sketch to build the steering assembly on our kart.

To assemble the the wheels we bolted together a block of aluminum and a waterjetted piece of quarter inch aluminum which connects to the steering column with a tie rod as shown.

As you can see, the kingpin bolt goes through both the aluminum block and the quarter inch aluminum to allow the wheels to turn. We bolted the wheel itself into a threaded hold in the end of the aluminum block with a spacer in between to allow the wheel to spin freely.

We attached the steering column to the frame through 3D printed bushings, where it is held in place by aluminum collars.

The brake cables are bolted to the pedal at the front of the frame which is held in place by eighth inch aluminum tabs. The cables and housing then run back to each rear wheel, where they connect to the brake calipers. To mount the brake calipers to the frame we again used quarter inch aluminum. Our original design had our brake calipers mounted under the frame. However, when we went to bolt them on we realized that they were too big and would drag on the ground. To fix this problem we cut more quarter inch aluminum on the band saw and mounted the calipers on top of the rotor as shown.

Going forward from here, we need to hook up our batteries, motor controllers, switches and throttle.