Make: Online reader Baz from Dublin, ireland, sent us this rad video of a low-tech robot lawn mower. He writes:
Self-propelled lawn mower guided by wrapping a string around a couple of posts so it mows a spiral of lawn. Quite hacky, but interesting idea!
In the MAKE offices we’ve been trying to guess what happens at the end. So far we’re thinking the mower flips over, or perhaps it rips its tether out of the ground, mowing wildly amok. What do you think happened when the rope ran out?
Of course, this project is an incredibly great contrast to the R/C Lawnbot we have on the cover of MAKE Volume 22 (and show you how to make inside the issue).

MAKE Volume 22, Remote Control Everything
Automate your world with remote control. From pet care to power outlets, from toys to telepresence, we’ll show you how to add a joystick, push-button, twist-knob, or timer to just about anything. Don’t forget, subscribers can always read the digital edition here.










Kill switches for the ignition system are easy to make, multiple switches ready to close the system dead could be installed. No strain on the rope mount and a kill switch could be rigged to close. The rope ends and the post contacts the side of the mower, a kill switch could be rigged to close. Possibilities are limitless.
The mower would just stop. Self-propelled mowers are not terribly powerful, and the wheels don’t have deep treads or much weight riding on them, so the rope would just snug itself against the tether post and the mower will sit there spinning its single drive wheel. It could dig a tiny rut if you left it that way long enough.
For a kill switch, most mowers already have one built in. I don’t see where it is on this one, but typical modern mowers have a deadman bar parallel to the top of the handle. A good safety feature would be to secure this deadman switch with a clamp, then run a line slightly longer than the tether from there to the central post. If the mower gets more than a tether length from the post, the secondary line would pull the clamp off the handle and kill the power.
I have thought about doing this (usually while mowing in high heat/humidity), but have too many trees. Even after mowing the corners, the crop circle mow pattern is a little weird.
I would skip the safety features and just stay out there with it. It shouldn’t be left unattended anyway.
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