How to replace KM4 drive wheel nuts on MiR600 and MiR1350

MiR600 and MiR1350 are equipped with through-going drive shafts on the bogies. Both robots uses KM4 locknuts with corresponding MB4 lock washers on the front of the shaft in front of the drive wheel.

It is recommended to check the KM4 nuts and replace the nuts and the corresponding lock washers as part of regular maintenance, or if you suspect that the nuts have become loose.

Things you will need

• The locknuts, front drive wheel kit from MiR (part number 450716)

• The KM4 crimp tool and locknut socket from MiR (part number 450717)

• Torque wrench ranging from 19 to 24 Nm

• Paint marker

Kit contents

• 2 × KM4 locknuts

• 2 × MB4 lock washers

Before replacing the locknuts

1. Press the two buttons on the side hatch.

   

2. Pull open the hatch.

   

3. Disconnect the status light cable.

   

4. Turn the two hinges in the bottom corners to release the hatch.

   

5. Remove the hatch from the robot.

   

6. Turn off the robot, and disconnect the battery in the left side compartment. To disconnect the battery, pull out the Battery lock pin, and pull the Battery lever downwards until the Battery lock pin is in the middle position.

   

7. Raise the robot above ground and use a support block to keep one end lifted—see the Maintenance section in the user guide for instructions on how to lift the robot safely. Make sure the support block is supporting the robot's chassis.

   

Replacing the KM4 locknut

1. Remove the KM4 nut and the MB4 lock washer. Use a KM4 socket.

   

2. Mount the new MB4 washer onto the shaft. Make sure the internal tab is in contact with the right side of the indent on the shaft.

   

3. Mount the new KM4 locknut to the drive shaft and tighten the KM4 nut to 24 Nm.

   Make sure the MB4 lock washer is not turning with the locknut. If it does start turning, the internal tab is likely broken, bent, or displaced and must be replaced with a new lock washer.

   

4. Align the MB4 washer with the KM4 nut so a tab on the washer lines up with a groove in the nut. Gently tighten the locknut so the tab closest to fitting aligns. If you tighten the locknut so a whole tab passes a groove, the lock washer will crack and must be replaced.

   

5. Bend the tab down into the groove of the nut. Use the KM4 crimp tool:

   • Place the tool as shown so it has a 90° angle to the tab, and the pointed tip is placed at the tab you have aligned with the locknut.

   • Tighten the tool handles together.

   • Tip the tool away from the tab, towards the spring on the tool, until the tab is fully pushed into the locknut.

   

6. Verify that the tab is correctly bent 90° into the locknut.

   

7. Mark the position of the locknut and lock washer relative to the shaft using a paint marker. This ensures that you can easily identify if the nut is starting to come loose during regular maintenance inspections.

   

8. Reassemble the robot by following the steps in Before replacing the locknuts in reverse.

Testing

While the robot is driving, verify that it drives straight and the drive wheels are stable and silent. You can consider driving the robot without the side covers to better see the drive wheels.