Aerator - Mecanum Wheels
Mecanum wheels give the robot an amazing range of movements. This is very helpful as straight line ability and rows are important when drilling holes into the grass. We are not so interested in speed but straight line accuracy for this robot.
The rotating wheel and individual rotating rollers allow the robot to move at 90° angles when wheel are driven in the right combination of directions.
The mower requires 4 mecanum wheels to make a 90° movement, but 2 mecanum wheels can also be used at the front (2 standard wheels at the back) for standard turning.
Mecanum Wheel Overview
The TPU rollers are printed with 100% infill (at lesser infill levels the rollers become squishy and the frame rubs along the ground). The rollers are completed with 2x M5 bearings and washers. A 100mm M5 bolts is used to secure the roller to the wheel plates
Hub and Axle
The axle needs to be made from Aluminum round stock, or alternatively can be purchased in the online shop.
The hub is printed in PLA (or other similar material you choose). I used a 1.6mm line width and 30% infill.
The axle is secured to the hub using an M5x70mm bolt. The bolt passes through the aluminum axle and locates into the hub on the other side. An M5 nylon bolt can be used to secure the axle to the hub but this wont be accessible later.
Front and Back Plates
The 2 plates (front and back) are the same on the wheel. There are two wheel orientations which require the different plate types. The plates can be printed in PLA or another material of your choosing. To print I used a 1.6mm line width with 30-40% infill, 0.2mm layer height. There is no need for any support structure if the plate is printed face down.
The plates are secured to the hub using long M3x50mm bolts, washers and nylon locking nuts.
With the hub, axle and plates installed, the rollers can now be added to the wheel. Please use M5 washers between the bearings and the plates to ensure the roller has a free movement.
4 wheels are required for the 90° sideways movement. The wheel types and locations are shown here.
Movement Range of 4 Mecanum wheels
the following movements can be made by rotating the wheels individually as shown