The difference with all those other tools is that you are always there when it runs. You are not there when the robot lawnmower is running and some cat jumps your fence, which is why it should not harm the cat.

You are kind of correct that the rpm of the robot mower blades are faster, but the blades are much lighter and most mowers even have swiveling blades that are only held straight by the centrifugal force, so they will just swivel away when they hit something.

The blades are not much more than razor blades that are mounted on a plastic disc with one screw each. You wouldn’t want to put your hand into the spinning blade, which is very hard to do anyway, but there is just not enough power to throw rocks with any significant force.

I would be able to put my finger in the way of the blades if they were completely blunt and I would not get hurt very much if at all, doing the same thing on a normal mower would be a very different story.

Yes, I have heard about that too, which is why I only let mine run at daytime.

Lawnmower robots have much smaller blades with less inertia. I don’t doubt a direct hit would hurt, but rocks just won’t get thrown very fast by it. A direct hit would also be pretty hard to achieve because the skirt stops anything big from getting under the robot and the blades stop immediately when it gets lifted up.

Just imagine how many lawsuits the manufacturers would have to deal with if these things were only slightly unsafe.

I think it is because the exhaust is much cleaner than with diesel or gasoline.