In Part 3 we’re going to verify proper motor operation and install the wheels. The following items will be needed:
- 4 – wheels
- 4 – wheel hubs
- 4 – M4x8 screws
- 4 – M3x10 screws
- 4 – custom motor shaft adapter sleeves
- UartBee USB board
- USB Cable
- Host computer for programming
The host computer needs the Arduino IDE, UartBee serial driver and Hercules motor libraries installed as described in this post: Project Hercules – Host Computer Setup
The hubs included in the Hercules kit do not fit the motor shafts. The hubs are designed for a much larger shaft. If you install the hubs as provided then the wheels will be significantly off center an wobble over half a centimeter. This is of course completely unacceptable. This problem has been included in our overall list of comments about the Hercules product. To resolve this problem we designed and printed on a 3D printer a custom sleeve for the motor shaft. This sleeve centers the shaft in the hub and allows for smooth rotation.
1. Upload motor test program
Before you start, set the chassis squarely on a solid surface. Don’t try to hold the chassis while uploading.
After preparing a host computer (see Project Hercules – Host Computer Setup), connect the UartBee to the programming cable and to the host via the USB cable. Compile and download the motor test program from here:
Motor Forward Test Program
As soon as the program has been uploaded the for motors will start turning.
2. Fix motor directions
Check each motor and verify that it is turning in a forward direction. For any motor that is reversed complete the following procedure.
Disconnect UartsBee and turn off power switch so that robot is powered down.
Gently disconnect the motor power connector for the reversed motor. Place the connector on the table. Turn so that the slots are up.
Using a small screwdriver, gently release each pin by pressing in the top of the slot and gently pulling the wire out of the housing.
Now swap the wires and slid them back into the connector housing.
Reconnect to the controller.
Power up the robot and verify that the motor is now turning in the forward direction.
Repeat this procedure for each reversed motor.
3. Install shaft adapter sleeves
Power down the robot. Do not turn power on while working on this step.
Turn the motor shaft with a pair of pliers so that the flat side to the side.
Place a drop or two of superglue along the curved portion of the motor shaft. Do not put glue on the flat portion.
Place a drop or two of superglue inside the sleeve adapter.
Slide the adapter on to the motor shaft. The opening in the adapter should be on the flat side of the shaft. Slide the sleeve down so that it is flush with the end of the shaft.
Repeat this process for the other thee motor shafts.
Let the superglue dry for 10 minutes.
4. Mount hubs on motor shafts
Next step is to mount the hubs on the motor shafts. This photo shows a hub.
Start a M3x10 bolt in the small hole on the side of the hub. Just a turn or two is needed to start the bolt but no far enough to enter the center column.
Slide the hub over the motor shaft and sleeve. The lock screw should be oriented to the flat side of the shaft.
The fit should be very tight. Slide the hub down until it almost covers the sleeve and the lock screw is over the hole in the flat side of the shaft.
Tighten the lock screw so it goes into the motor shaft and securely holds the hub to the shaft.
Repeat for the remaining three wheels.
5. Mount wheels on hubs
Take a wheel, M4x8 bolt and lock washer.
Place the wheel on the hub and turn until the hex shape on the hub slides into the wheel.
Secure the wheel to the hub with the M4x8 bolt and lock washer. Do not over tighten the bolt as we don’t want to crack the wheel.
While holding the robot firmly in two hands, turn the robot on. In a few seconds the wheels will start turning. Observe each wheel. Verify that it is turning forward and that the wheel is not “wobbly”. Turn the robot off.
6. Upload test program
Before you start, set the robot squarely on a solid surface. Hold the robot with two hands and be prepared for it to start moving.
From the host computer (see Project Hercules – Host Computer Setup), connect the UartBee to the programming cable and to the host via the USB cable. Compile and download the random test program from here:
Randowm Test Program
As soon as the program has been uploaded the wheels will start turning. Disconnect the UartsBee and place the robot on the floor to roam around.