This guide describes how to update the drive wheel attachment on MiR500 and MiR1000 robots.

MiR500 and MiR1000 robots have been produced with four different wheel attachment designs, which in this guide are referred to as designs A, B, C, and D. Design D is the current standard, and it is backward compatible with all older designs.

We encourage all MiR500 and MiR1000 users to update their robot to design D as this secures the drive wheel better than former designs.

Determining what spare part kit you need

All spare part kits transform the wheel attachment design of your robot to design D, but as the older designs differ, the spare part kits are different as well, so you need to first identify what design your robot has before ordering. You do that by looking at the wheel attachment itself.

Design A (spare part number 450266)

The wheel hub is attached to the gear shaft with five screws.

Design B (spare part number 450542)

The wheel hub is secured to the gear shaft with a bolt.

Design C (spare part number 450543)

The wheel hub is secured to the gear shaft with a nut and Nord-Lock washers.

Design D (the current standard)

Similar to design C, but the wheel hub is now secured with all-metal lock nuts.

There are also small differences in the side and corner shields and the bogie in different robot versions, so your robot may appear slightly different than the robot used in the images, but the procedure is the same unless otherwise specified.

Things you will need

• The correct upgrade kit from MiR. See Determining what spare part kit you need for an overview of the kits.

• SKF LGMT2 roller bearing grease, or other grease with same properties (see https://www.skf.com/group/products/lubrication-solutions/lubricants/general-purpose-industrial-and-automotive-nlgi-2-grease/index.html)

• A torque wrench with range 43–85 Nm (up to 120 Nm for design A), with the following exchangeable bits:

  • 13 mm hex

  • 17 mm hex

  • 19 mm hex

  • 22 mm hex

• A screwdriver with the following exchangeable bits: 

  • 4 mm hex

  • A flat-head bit

• A rubber hammer

• A mandrel

• A piece of wood or other firm material to lift the robot (must be thicker than 25 mm to raise the robot from the ground)

• Loctite 2400 threadlocking adhesive, or other adhesive with same properties (see https://www.henkel-adhesives.com/dk/en/product/threadlockers/loctite_2400.html)

Kit contents

Kit 450266 for design A

• 2 × needle bearings

• 2 × inner ring of needle roller bearing (28×40×7 mm gland)

• 2 × shaft bushings

• 8 × M14 wheel bolts

• 2 × wheel plates

• 2 × gear shafts

• 2 × M14 Nord-Lock washers

• 2 × M12 Nord-Lock washers

• 2 × M14 all-metal lock nuts

• 2 × M12 all-metal lock nuts

• 4 × motor cable clips

• 4 × 6×4×22 mm keys

• 2 × 6×6×50 mm keys

Kit 450542 for design B

• 2 × needle bearings

• 2 × inner ring of needle roller bearing (28×40×7 mm gland)

• 2 × shaft bushings

• 2 × gear shafts

• 2 × M14 Nord-Lock washers

• 2 × M12 Nord-Lock washers

• 2 × M14 all-metal lock nuts

• 2 × M12 all-metal lock nuts

• 4 × motor cable clips

• 4 × 6×4×22 mm keys

• 2 × 6×6×50 mm keys

Kit 450543 for design C

• 2 × M14 Nord-Lock washers

• 2 × M12 Nord-Lock washers

• 2 × M14 all-metal lock nuts

• 2 × M12 all-metal lock nuts

Before replacing the wheel hub and gear shaft

1. Turn off the robot, and disconnect the battery. To disconnect the battery, open the rear compartment, and turn the Battery disconnect switch to the Off position.

   

2. Remove the side compartment hatch. To do this, turn the two screws 90˚ with a flat-head screwdriver, and pull open the hatch.

   

3. Remove the compartment hatch. To do this, disconnect the status light cable, and turn the two hinges in the bottom corners.

    

4. Repeat with the other side compartment hatch.

5. Remove the front compartment hatch. To do this, press the two buttons on the front hatch, and pull open the hatch.

    

6. Remove the compartment hatch. To do this, disconnect the status light cable, and turn the two hinges in the bottom corners.

   

Removing the front corner shields

1. Press the Emergency stop button on the front corner shields. After reassembling, remember to release the buttons again.

2. Disconnect the cables plugged into the corner shields. Mark which cables should be plugged into which sockets, or take a picture to make sure you plug in the cables correctly when reassembling the robot.

3. Remove the four screws from each corner shield using a 4 mm Hex screwdriver.

   

4. Remove the corner shields. It may require some force to disconnect the shield from the corner bumper. Pull it downward firmly to remove it from the bumper.

   

Pulling out the bogie arm

1. Raise the robot above ground, and use a piece of wood or other firm material to keep it lifted. The drive wheel must not be in contact with the floor.

   

2. Remove the bogie bolt, using a 17 mm wrench. When reassembling, apply Loctite 2400 to the bolt, and tighten it to a torque of 43 Nm.

   Loctite and many other threadlocking adhesives are toxic substances that can cause skin, eye, throat, or digestive tract irritation to personnel upon contact, inhalation, or ingestion.

   • Read the safety data sheet for the adhesive product before applying it.

   • Avoid direct contact with the adhesive.

   • Apply the adhesive in a well-ventilated area.

   

3. Pull out the wheel and bogie arm slightly. Pull out the bogie arm enough to make it possible to gain access behind the wheel gearing.

   Be careful not to pull any wires while pulling out the bogie arm. If necessary, unplug any wires that are not long enough to let you pull out the bogie far enough for you to reach behind it.

    

4. Disconnect the following cables located behind the bogie, beneath the center compartment:

   Pos.	Description	Pos.	Description
   1	Brake feedback cable	2	Brake power cable
   3	Motor encoder cable

   

5. Disconnect the motor power cable and the hall sensor cable. The bogie arm with the motor is now detached.

   

Disassembling the drive wheel from the gear shaft

The procedure to disassemble the drive wheel differs in the first step for robots with designs A, B, and C.

1. If you have design A: Disassemble the wheel hub from the drive wheel by unscrewing the four lug nuts with a 19 mm wrench. Discard the wheel hub.

   

   If you have desing B: Remove the center fixing bolt from the gear shaft using a 17 mm socket wrench. Discard the bolt. Remove the gear shaft from the drive wheel. You do not need to disassemble the wheel hub from the drive wheel.

   

   If you have design C: Remove the nut from the gear shaft using a 22 mm socket wrench. Discard the nut. Remove the gear shaft from the wheel hub. You do not need to disassemble the wheel hub from the drive wheel.

   

2. Remove the bolt from the gear shaft using a 13 mm socket wrench

   

3. Remove the drive shaft and the wheel from the gearbox using a hammer and mandrel.

   

Assembling the gear shaft in the gear box

1. Replace the roller bearings if you have kit number 450266 or 450542. This is not a mandatory step, but now that you have access to the bearings, it is a good opportunity to replace them in case they are starting to wear down. To replace the bearings, follow these steps:

   1. Use a pair of circlip pliers to gently remove the locking clip in front of the bearings. Some models may not have the locking clip. In which case, you can disregard this step.

   2. Remove the roller bearings, and replace them with the new set included in the kit.

      

   3. Push the new roller bearings in place, and lock them in by reusing the circlip if one was also used before.

   4. Lubricate the new roller bearings with 1.5 cm3 SKF LGMT2.

2. Assemble the gear shaft, inner ring of needle roller bearing, shaft bushing, and a (6 × 6 × 50 mm) parallel key.

   • If you have a robot with design A or B, use the gear shaft included in the kit.

   • If you have a robot with design C, use the robot's current gear shaft.

   • If you replaced the roller bearings in the previous step, use the new inner ring included in the kit and discard the old one.

   • If you did not replace the roller bearings, reuse the robot's current inner ring and keep the inner ring from the kit with the unused roller bearings. The roller bearing and inner ring must have matching tolerances.

   

   Pos.	Description	Pos.	Description
   1	Gear shaft	2	6 × 6 × 50 parallel key
   3	Inner ring of needle roller bearing	4	Shaft brushing

3. Insert the gear shaft assembly through the bearing housing and into the gear box. Make sure to fit the parallel key into the keyway of the gear box.

   

4. Use a rubber hammer to position the gear shaft properly. The other end of the gear shaft must be visible on the other side of the bogie.

5. Place a M12 Nord-Lock washer included in the kit on the thread of the gear shaft protruding from the other side of the bogie.

   

6. Screw an M12 all-metal lock nut included in the kit on the thread of the gear shaft, and tighten to a torque of 70 Nm using a 19 mm torque wrench.

   

Assembling the new wheel hub on drive wheel

If you have a robot with a design B or C, you do not need to reassemble the drive wheel and wheel hub. They are already correctly assembled, and you can continue to Mounting the drive wheel subassembly onto the gear shaft.

1. Ensure the correct orientation of the driving wheel relative to the wheel hub. This is verified by checking that the inner shaft hole of the driving wheel fits the recess of the wheel hub and that the spherical part of the wheel lug bolts fit the countersink around the drive wheel bolt holes.

2. Apply Loctite 2400 to the thread of the four wheel lug bolts included in the kit.

   Loctite and many other threadlocking adhesives are toxic substances that can cause skin, eye, throat, or digestive tract irritation to personnel upon contact, inhalation, or ingestion.

   • Read the safety data sheet for the adhesive product before applying it.

   • Avoid direct contact with the adhesive.

   • Apply the adhesive in a well-ventilated area.

3. Mount the four wheel lug bolts fixing the drive wheel to the wheel hub, and tighten the wheel bolts to a torque of 120 Nm using a 17 mm torque wrench. To lock the wheel hub rotationally while applying 120 Nm to the wheel lug bolts, the wheel hub can temporarily be mounted on the gear shaft. The following steps describe how to do this:

   

   1. Insert two (6 × 4 × 22 mm) parallel keys into the keyways on the bearing housing side of the gear shaft.
      

   2. Mount the drive wheel subassembly temporarily on the gear shaft by fitting the parallel keys into the keyway of the wheel hub. Face the wheel subassembly so the wheel hub is on the inner side and the heads of the lug bolts are facing outwards. If it is impossible to mount like this, remove one of the keys, mount the wheel subassembly, and then insert the second key afterward.
      

   3. Cross-tighten the wheel lug bolts to a torque of 120 Nm using a 17 mm torque wrench.

   4. Remove the drive wheel subassembly from the gear shaft.

Mounting the drive wheel subassembly onto the gear shaft

1. Insert two (6 × 4 × 22 mm) parallel keys into the keyways on the bearing housing side of the gear shaft.

   

2. Mount the drive wheel subassembly on the gear shaft by fitting the parallel keys into the keyway of the wheel hub. Face the wheel subassembly so the heads of the lug bolts are on the inner side and the wheel hub is facing outwards. If it is impossible to mount like this, remove one of the keys, mount the wheel subassembly, and then insert the second key afterward.

   

3. Place a M14 Nord-Lock washer included in the kit on the thread of the gear shaft.

   

4. Screw an M14 all-metal lock nut included in the kit onto the thread of the gear shaft and tighten to a torque of 85 Nm with a 22 mm torque wrench.

    

5. Repeat the steps from step 1 of Pulling out the bogie arm to the end of Mounting the drive wheel subassembly onto the gear shaft with the other drive wheel.

6. If you have a robot with design A or B, fix motor cable clips included in the kit into the two top screw holes on the gear box.

   

7. Secure the motor power cable into the two clips. When you reassemble the robot, the clips and cable should be mounted within the robot as shown in the image below. The cable should be lifted as far from the ground as possible.

   

   If the power cables become worn out from being dragged, the robot may not drive correctly. After reassembling, make sure that the motor cables are not dragging against the ground. If so, rearrange the cables in the cable clips to make sure they stay lifted.
   

Reassembling and testing the robot

1. Follow the disassembly steps in reverse order from step 5 in Pulling out the bogie arm to the beginning of this document.

2. Once the robot is fully assembled, wait until the Loctite 2400 or other adhesive has hardened. See the use instructions on the product for the required waiting time.

3. Once the adhesive has hardened, reconnect the battery, and release the emergency stop buttons.

4. Calibrate the robot's Inertial Measurement Unit (IMU)—see How to calibrate the IMU.

5. Turn on the robot, and drive it in Manual mode. Ensure that the robot is driving as intended.