Rear wheel for Gardena R40LI Robot Lawn Mower

My robot lawnmower has a poor design for the rear wheel. When the lawnmower turns, it drags the wheel sideways. It tears up tracks in the lawn. And when it turns on my stone paving next to the lawn, it wears down the wheel. The wheel is no longer round, and it has even developed holes in it.

I have now designed a new rear wheel to solve these problems. I have constructed an omni wheel that has ten small wheels used when the lawnmower turns.

Before

After

Materials you'll need:

• Steel shaft (maximum 1.7 mm). I salvaged mine from an old, broken umbrella.
• Heat shrink tubing (13 mm). Optionally, to protect the small wheels.

Tools you'll need

• Torx T20 screwdriver
• Small bolt cutter or wire cutters
• Scissors
• Heat gun or hairdryer

Instructions

Unscrew the four screws that hold the existing wheel in place.

Remove the brackets from the wheel axle.

Unscrew the three screws and divide the wheel into two parts.
Remove the wheel axle, bearings, and rubber gaskets from the old wheel.

Print all parts. I used PETG.
0.2 mm layer height. 15% infill. No supports.

Cut the heat shrink tubing into approximately 18 mm long pieces and thread them onto the small wheels.
My heat shrink tubing was a bit too small, so I stretched it with scissors.

Rapidly heat the heat shrink tubing with a heat gun (or hairdryer) to secure it onto the small wheels. Be careful not to deform the wheels

Cut the steel shaft into pieces that are 25 mm long.

Place the small wheels on the inner plate. and position the outer plate on top of them, ensuring that the grooves on the inside align. Use the printed tube to align them.

Glue the outer plate and inner plate together to secure the small wheels.

Place a ball bearing on the wheel axle and press it into the printed tube.
Secure the other ball bearing in the lid of the tube.

Glue the lid onto the tube.

Attach the finished plates to the tube and ensure they are correctly positioned.
Glue all the parts together to secure them properly.

Mount the rubber gaskets on the tube ends and glue the ends onto the wheel to secure them.

The finished wheel.

Finally, mount the new wheel on your lawnmower.

With this new omni wheel, your robotic lawnmower should be able to maneuver more smoothly and hopefully avoid tearing up tracks in the lawn or getting damaged when turning on the stone paving.