Cut off the end of the power adapter that goes into the laptop.
Separate the wires so that you have several individual wires. Strip about an inch of insulation off the end of each wire.
Plug the power adapter in a wall outlet. Make sure that none of the wires are touching each other. Place the DC motor next to the power adapter to test the connections. Pick up the wires by the insulated parts and touch the wires from the adapter to different connection wires from the motor.
Make a note of which combination of wires gives enough power to spin the motor.
Unplug the adapter and affix the wires from the adapter to the appropriate motor wires with electrical tape.
Place the motor on the shovel handle so that the motor housing reaches approximately 2 inches above the bottom of the shovel handle. Affix the motor to the handle with the hose clamp and tighten the screw on the clamp to secure the motor.
Insert a screw through the clamp into the handle from the side. This is to prevent the clamp from rotating on the handle.
Cut the empty bleach bottle in half. The bottle's handle should be in the center of one of the halves.
Cut a hole approximately the same size as the shovel handle in the half of the bleach bottle without the handle. Slip the bottle onto the shovel handle.
Drill two or three holes in the empty bottle's neck and into the shovel handle to affix the handle to the bottle. Use screws to secure the combination.
Use the drill to make a hole through the top side of the PVC pipe cap. It should fit the drive shaft of the motor. Drill two additional holes on the sides of the cap for the trimmer string. They should be on opposite sides of the cap.
Slide a nut on the drive shaft and secure it to the top of the threading. Insert the drive shaft through the hole on the top of the PVC pipe cap. Secure the drive shaft by placing a nut on either side.
Use scissors to cut 6-inch pieces of trimmer string. Insert them through the holes on the sides of the PVC pipe cap. To secure the cap, tie a knot with the strings on the inside of the cap.
Use several zip ties to affix the laptop power adapter to the shovel handle.
When you are ready to use the weed trimmer, simply plug the adapter into an extension cord. Plug this extension cord into a power outlet.