Design

The Chassis

The new mower is going to be about the size of a normal lawnmower base, namely somewhere in the region of 600mm square. After thinking about my options for I while, I decided to go back to using wood for the base, more specifically 6mm marine ply. This is strong, readily available, weatherproof and easy to work with. It can easily support the weight of a lead-acid battery and will not shatter unlike some of the available plastics.

Mo will be rear-wheel drive. The drive wheels and battery will be at the back whereas the RF sensor and bump switches will be at the front. Steering will be differential but rather than having one castor, I decided to have two (near the front) for extra stability. The castors need to be relatively close together to achieve controllable steering but wide enough apart to prevent the mower tipping.

Once I had purchased a couple of castors and decided on the blade arrangement, the floor plan of the chassis was designed.

Mo Floorplan

A few things to note about the design:

• The drive motors and battery are at the back of the mower to give good traction.
• There are two castors rather than one at the front to give additional stability.
• The front edges of the mower are curved to aid stability and help with turning collisions.
• There are three cutting blades, each with a 14cm cutting diameter. The layout is such that a total cutting width of 31cm is available.
• There is room at the front to mount the RF pickup coils and bump sensors.