The various components evolved over time by trial and error, doing sketches here and there and somehow they all fitted
together as though they were designed as such!
I managed to purchase two identical second hand Nissan Skyline wiper motors and a 12 volt blower motor from a motor scrap yard dealer in Potchefstroom not too far from my home in Lichtenburg, Northwest Province, South Africa. The wheels are standard 170 mm diameter lawnmower wheels obtained from the local hardware store. Their traction is not all that good but they made a good start for the robot lawnmower project.
I used an old 386DX40 small sized computer for the "brains"
of the robot lawnmower. It's maybe a bit of an overkill but
it was simply available and I enjoy controlling the outside
world via the printer port. It is a cheap and easy method for computer control.
I used second hand YUASA Gel batteries which were replaced by new ones in computer UPS systems. Two 6 volt batteries were wired in parallel to supply sufficient power to the 386 PC via a silicon diode to drop the voltage down to approximately 5 volts required by the PC. No fancy voltage regulation at this stage but it must get the highest priority for the future. The third battery is a 12 volt battery used for the wiper motors, cutter motor and automotive switching relays.
All I/O control is done via the printer port (LPT1) of the onboard 386 PC.
I would love to share ideas with other robotics enthusiasts. I know my robot is very primitive and still needs a lot of
attention. The important thing to do in the near future is to replace the two balancing castors with a large third castor to assist with movement over grass. The small ones tend to get in the way.
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