Introduction
The forklift attachment lets your Rover lift and carry small objects. A continuous servo spins a lead screw, and the screw drives the fork up and down two towers. The shell clips straight onto the front of the Rover.
Before you start:
- Use a continuous rotation servo. A standard 180° positional servo only turns the screw half a turn, so the fork will barely move.
- Print the fork and screw at the same speed. Both come in Medium and Slow. Slow is stronger but lifts more slowly. Mismatched speeds have different threads and won't fit together.
Drag to rotate, scroll to zoom
Interactive 3D BuildOverview
The Finished Forklift
The forklift clips onto the front of the Rover. Drag to look around, scroll to zoom, then step through the build.
AccessoryMelonCubeA small cube for the forklift to pick up. Print one to use with the forklift activity.
What You'll Need
Parts:
- 1x 9g Micro Servo (continuous rotation)
- 1x Double-sided servo horn (from the servo's accessory bag)
- 2x Servo mounting screws (from the servo's accessory bag)
- 2x M3 x 10mm screws
Tools:
- Phillips Head Screwdriver
- M3 Allen Key
- Side Cutters
13D Print Your Parts
- 1x Shell
- 2x Tower
- 1x Top Plate
- 1x Fork Screw
- 1x Fork (same speed as the fork screw)
2Install the Servo
- Turn the shell upside down.
- Push the servo up into the shell from underneath, so the output shaft pokes up through the round hole between the two square tower holes.
- Fix it in place with the two servo mounting screws through the servo's tabs.
Cut one arm at the innermost hole and the other flush with the hub
3Attach the Servo Horn
- Use the double-sided servo horn (an arm on each side), not the single-sided one.
- Using side cutters, cut one arm off at the innermost hole and cut the other arm off flush with the hub. The slot on the underside of the fork screw only has room for the hub and one short stub, so a horn with a stub on both sides won't go in without breaking the screw.
- Press the trimmed horn onto the servo shaft. It doesn't need a screw, as the fork screw holds it in place.
- Check the fit: hold the fork screw over the horn and line the stub up with the slot. The screw should sit down flat. If it doesn't, trim the stub a little shorter.
4Attach the Fork
- Twist the fork screw into the fork's centre hole, slotted end down, until the fork is about halfway along the screw.
- Point the prongs forward, away from the curved clip on the shell.
- Lower the screw onto the servo horn, turning it slightly until the horn drops into the slot.
5Slide in the Towers
- Slide each tower in from underneath the shell, up through its square hole in the shell and the matching hole in the fork.
- Each tower has a missing edge on its tip. Face it towards the servo, or the tower won't fit.
- Push both towers all the way in, until the lip at the bottom sits against the shell.
6Attach the Top Plate
- Lower the top plate onto the tops of the towers, with the pin on top of the fork screw in the middle hole.
- Screw it down with the two M3 x 10mm screws. They cut their own thread into the towers, so stop as soon as they're snug.
Fit and Test It
- Clip the shell onto the front of the Rover.
- Plug the servo into the right servo port on the back of the Rover. Match the brown wire to the - on the port icon.
- In the Code Editor, set the right servo to -90 for one second to raise the fork, then 0 to stop it. Set it to 90 to lower it again.
Because it's a continuous servo, the value sets speed and direction rather than position. -90 and 90 are full speed in each direction and 0 stops it. To reach a particular height, control how long the servo runs. The forklift activity below walks through an example.
Troubleshooting
- The fork only moves a little, then stops: you're using a 180° positional servo. Swap it for a continuous rotation servo.
- The servo runs but the fork doesn't move: the horn isn't seated in the slot under the fork screw. Lift the top plate off and check the screw sits flat on the horn.
- The fork binds or won't thread: check the fork and screw are the same speed, and that both towers are pushed all the way in.
- The fork screw won't sit on the horn: make sure the second arm is cut off flush with the hub, and trim the remaining stub a little shorter. Don't force it, or the base of the screw can break.
