In order for Lawnny 5 to live up to his name, he really needs to learn how to mow the lawn. So for the past few days I've been working on connecting him up to my 30" Toro TimeMaster lawnmower.

Here are the early results of this work:

As you can probably tell, Lawnny appears to have no trouble slinging this beast of a mower around, and it's starting to take the shape of capable lawn tractor.

Starting Small

A portion of my lawn has a roughly 20° slope, so my first concern before investing a ton more time into the project was to find out if Lawnny was capable of pushing this chonky mower (150+ lbs) up that slope. This 30" mower is about as big and heavy as it gets for a residential walk-behind mower, so I figured if it could handle this beast it would be capable of handling just about any other mower you could throw at it.

To run this test I started as simple as possible— I put the mower at the bottom of the hill, pulled up Lawnny behind it and simply nudged it up the hill. It pushed the mower up the hill without even a hint of a struggle— absolutely no change in motor RPM. Even better, it appeared to have plenty of traction on the wet lawn and didn't leave any marks. This resounding success meant I could now invest the time into making a more permanent mount.

The Mounting System

By now you probably know that Lawnny is based on an attachment system built around 2" hitch receivers. But how to you connect a 2" receiver to a piece of equipment with wheels?

Like everything else with Lawnny, I wanted the mounting system to be as versatile as possible, so I defined the following requirements for it:

1. The mounting system should not require any permanent changes to equipment. If this project fails miserably, I want to be able to use my equipment again.
2. The mounting system should not interfere with the ability to make adjustments to the equipment. For example: I don't want to lose the ability to adjust the mower deck height.
3. The mounting system should be able to accommodate equipment with varying wheel-bases and widths.

Addressing requirements 1 and 2 were simple— attach the frame to the wheel axles. The entire weight of the machine is already supported by the wheels, so I know those mounting points are going to be strong enough. And the deck height of the mower is adjusted by changing the height of the wheel axles. It was a no-brainer decision.

Requirement 3 was a bit more complicated. I contemplated all sorts of ideas and one of the first that came to mind was to use something like Unistrut. But my rudimentary and error-prone organic physics simulator (my brain) ran some virtual simulations and determined that the Unistrut probably wouldn't be stiff enough (specifically in the torsion axis).

I started to imagine other things that were easy to adjust yet capable of handling extremely heavy loads, when it hit me— a forklift. With this in mind I set out to create a mount that could be adjusted like a forklift, and this is what I came up with:

The "forks" (the supports in this case) can slide from side-to-side to accommodate equipment of differing widths, and are held in place with some simple set screws. The supports can then be attached to the equipment frame via any means necessary— in this case (at least at the moment) they are attached with some u-bolts.

The Mower Frame

You'll also notice from the picture above how the frame of the mower attaches to the wheel axles and is easily removable with a few nuts and bolts to return the mower back to original.

Also notice how the adjustment levers for the mower deck are easily accessible. To keep those levers free of interference with the frame was a bit of a challenge, and frankly the right-angles aren't exactly structurally optimal. But the frame is surprisingly stiff already, and a few more added supports should shore it up to be pretty bulletproof.

What's next?

Now that I have a mounting system which is able to account for differing wheel widths, I'll probably whip up another mounting frame that allows me to attach to the wheels of my snow blower.

I also received my Luxonis OAK-1 camera today! I'm extremely excited to start using its edge computer vision capabilities to track my movements so Lawnny can follow me around yard while carrying heavy stuff.