I started drawing up what the robot lawn mower would look like if we didn’t care about separating the compass from the electric motors. Removing this constraint allows several design efficiencies, some of which I was not expecting.
I decided to use two battery bays on version 5 because I had to mount a mast smack dab in the middle of the chassis. I didn’t want to mount it on a removable lid because it would be cumbersome to remove to get access to the batteries. Instead, I put hinged doors on both bays.
It looks neat in the picture above, but what you don’t see is all the wires running through my chassis tubes between bays to connect the batteries and all the signal wires run through the mast weldment up to the control enclosure. It started getting ridiculous drawing all of that up.
A separate design constraint I’ve been trying to achieve is to keep the wheel base of the robot to a minimum for handling reasons. Unfortunately, the mower deck design I settled on has a motor in the middle of the deck that is a pain to locate such that it doesn’t interfere with the battery bays.
Because I was splitting the battery bays anyway, I positioned the mower deck the way you see in the version 5 picture above. One downside to doing this is that the mower deck is pointing backward from what you see on virtually every riding mower.
Combining the battery bays let me rotate the mower deck 180º. In the back of my mind I have been worrying the backward orientation of the mower deck might cause performance issues. Now we won’t have to find out.
Additionally, both power and control enclosures can be mounted directly to the battery bay, which will drastically shorten the wire runs I’ll have to make. I’m actually excited to start drawing wires again. Things aren’t so claustrophobic anymore.
And on top of all the benefits above, the chassis weldment went from having 28 total parts to 15. Not too bad!
The Mower Project 