Introduction
The bulldozer attachment lets your Rover push objects around using a sturdy blade. It's built on a printed rover shell that takes the place of the Rover's own shell, and is powered by a continuous servo motor. The servo turns a lead screw, and the pushing shaft on the screw pushes the arms to lift and lower the bucket. This guide will walk you through printing and assembling the attachment step by step.
Before you start:
- Use a continuous rotation servo. A standard 180° positional servo only turns the screw half a turn, so the bucket will barely move.
- Left and right are as seen from the back of the Rover, looking forward. The left and right arms are different parts (their counterbored holes are on opposite faces), so check which is which before you start.
- The arms and the servo mount swing on their screws. When a step says to screw something on, stop as soon as the screw is snug and check the part still moves freely.
Drag to rotate, scroll to zoom
Interactive 3D BuildOverview
The Finished Bulldozer
The bulldozer is built on a rover shell that takes the place of the Rover's own shell. A continuous servo turns a lead screw, and the pushing shaft on the screw lifts and lowers the bucket. Drag to look around, then step through the build.
What You'll Need
Parts:
- 1x Micro Servo (continuous rotation)
- 1x Single-arm servo horn (from the servo's accessory bag)
- 2x Servo mounting screws (from the servo's accessory bag)
- 12x M3 x 8mm screws
- 2x M3 nuts
Tools:
- Phillips Head Screwdriver
- M3 Allen Key
- Side Cutters (to trim the servo horn)
Thingiverse
Printables
Makerworld13D Print Your Parts
- 1x Left Arm
- 1x Right Arm
- 1x Bucket
- 1x Servo Mount
- 1x Servo Mount Roof
- 1x Screw
- 1x Pushing Shaft
- 1x Rover Shell
2Attach the Arms
- Hold the rover shell with its two tall ears at the back. The arms go along each side of the shell, with their long straight edges on top and their curved ends pointing forward and down.
- Put the left arm on the left and the right arm on the right (looking from the back of the Rover to the front). The counterbored holes face outwards.
- Screw each arm's back hole to the hole in the side of the shell, just in front of the ear, with an M3 x 8mm screw from the outside. Stop when it's snug, and check the arm still swings up and down freely.
- Push an M3 nut into the slot near the front end of each arm, so it lines up with the hole in the arm's front end. These nuts hold the bucket on.
3Attach the Bucket
- Hold the bucket against the front ends of the arms, with the curved blade facing forward and the two counterbored holes lined up with the arm holes.
- Screw it on with two M3 x 8mm screws from the front, through the bucket and into the nuts in the arms.
- Check the fit: the screw heads sit down in their counterbores, and the bucket is square across both arms.
4Install the Servo
- Slide the servo into the pocket in the servo mount, with the output shaft pointing out of the open end of the mount, next to the half-round cut-out.
- Secure it with the two servo mounting screws through the servo's tabs.
- Use a single-arm servo horn. The horn has to fit in the pocket in the face of the screw, which only reaches about 7mm from the centre, so trim the arm off at the innermost hole with side cutters.
- Press the horn onto the servo shaft. It doesn't need a screw.
- Push the screw onto the horn, flange first, turning it until the horn drops into the pocket and the screw sits flat.
5Attach the Servo Mount Roof
- Push the servo mount roof down onto the servo mount. The fit should be tight, and the screw should click into place in the half-round cut-out.
- Secure the roof and the servo mount together using four M3 x 8mm screws: two down through the top of the roof and two up through the bottom of the mount.
- Check the fit: the screw should turn freely when you twist its end by hand.
6Attach the Pushing Shaft
- Twist the pushing shaft's threaded centre onto the end of the screw, with the cross bar running side to side.
- Screw it partway along the screw.
Final assembly
7Final Assembly
- Lower the servo assembly between the two ears at the back of the shell, with the screw pointing forward between the arms.
- Screw it to the ears with two M3 x 8mm screws, one from the outside of each ear into the side holes of the servo mount.
- Line the ends of the pushing shaft's cross bar up with the middle holes in the arms. Lift the bucket a little or turn the pushing shaft along the screw until they line up.
- Screw through each arm's middle hole into the end of the cross bar with the last two M3 x 8mm screws, from the outside.
- Check the fit: with all four screws snug, the servo mount can still tilt between the ears and the bucket can still move up and down.
Fit and Test It
- Take the Rover's own shell off and clip the bulldozer's rover shell on in its place, with the bucket at the front and the ears at the back.
- 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 lift the bucket, 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 lift the bucket a particular amount, control how long the servo runs, and stop it before the bucket reaches the top or the ground.
Troubleshooting
- The bucket 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 bucket doesn't move: the horn isn't seated in the pocket in the screw. Take the roof off and check the screw sits flat on the horn.
- The screw won't sit flat on the horn: trim the horn arm a little shorter.
- The bucket moves the wrong way: swap the values in your program (use -90 to lift and 90 to lower).
- The bucket is stiff or jerky: one of the pivot screws is too tight. Loosen the arm and ear screws a little until everything swings freely.
You're Done!
Your bulldozer attachment is fully assembled and ready to fit to your Micromelon Rover. Try pushing lightweight objects like ping pong balls or small blocks around a course. You can program the servo to raise and lower the blade using the Code Editor.
