PARTS Mini-Sumo Robot Kit: Mechanics

Assembling the Wheels

1. Match the two small holes in the wheels with two of the holes in the servo horn that came with your servos.

2. Enlarge the matching holes in the servo horn by drilling them out with a 3/32 inch drill bit.

3. Attach the wheel to the servo horn with two 4-40 countersunk screws. You will have to push the screws as you turn them and they will thread themselves into the plastic of the horn.

4. Tighten a 4-40 nut onto each of the screws to lock everything in place. Note: unless the servos are perfectly centered, the nuts will rub on the chassis. If you used the correct size drill in step 2, the screws should self-tap and hold fine without the nuts.

5. Stretch the rubber O-ring onto the wheel.



Mounting the Servos and Assembling the Chassis

The servos must be mounted very accurately on the chassis. If not, there will not be enough space for the nuts that hold the wheels to the horns to clear the chassis. Also, if the servos are mounted too far toward the rear of the chassis, the robot will be to long to qualify in competition (100 MM limit). Too far toward the front and the robot will not be able to push it's opponent effectively.

1. Clean the chassis and servos with Windex or rubbing alcohol to make certain the tape sticks well.

2. Using the smallest piece of double stick tape, stick the two servos together, back to back. Keep the servos on a flat surface to make certain that they line up exactly with each other.

3. Attach the wheels to the servos with the screws that came with the servos.


4. With the front of the chassis (the part with the 45' bend) pointing straight up, tape the back of the chassis (the part with the 90' bend) to the work surface with masking tape or Scotch tape. Don't use the tape that came with the robot kit

5. With the wheels sitting on the work surface, place the servos against the chassis with the servo wires toward the back of the robot chassis. Using a sharp tipped marker, mark where the forward edge of the servos lines up with the chassis.

6. Remove the servos and untape the chassis from the work surface. Mark a line lengthwise down the middle of the chassis. The chassis is 80mm wide, so the mark is 40 mm from either edge.

7. Set the servo and wheel assembly on the chassis, lining up the gap between the servos with the center line, and the front of the servos with the line that you made in step 5. Check to make certain that everything is centered and square, the tires do not stick out past the back of the robot chassis, and the wheel nuts do not hit the edge of the chassis..

8. If everything lines up, clean the servos with Windex or alcohol and apply one piece of double stick tape to each of the servos.

9. Very carefully, attach the servos to the chassis, using the marker lines for alignment. Remember, you only get one chance with the tape. Take your time, this step is very important.

10. Attach the four 7/8 inch aluminum stand-offs to the chassis with four 4-40 pan head screws. Do not tighten the screws yet, just put them in loosely.

Next Step

  last updated 3/1/2001