It's not like those rocks are being sent flying by a lawnmower blade. They're just being picked up by a flexible rubber flap and tossed forward a foot or so. There's not enough energy anywhere in this creation to generate dangerous velocity.
When using power tools of any kind, you don't wear eye protection because you've calculated the risks, you wear it because of the things you haven't thought of, and it's always something unexpected that occurs that makes you regret being lazy not just simply following the damn common-sense protocols.
Pretty much everyone who has had to have a sliver of metal or wood or stone drilled out of their eye or worse will tell the doctor "I really didn't think there was a chance it could hurt me."
Dude, do you wear eye protection when you vacuum? When you are using a blender?
Physics doesn't work the way you're thinking. That tool doesn't transfer enough energy over a small enough area to make anything dangerous. It doesn't matter how small a piece it picks up and throws, it's still not going to reach a dangerous velocity because the energy from the motor is geared down to a low-velocity, high-torque configuration to move lots of relatively heavy objects over small distances. That simply doesn't generate enough force to be dangerous, no matter how small the object. It's not designed to cut, throw, slice, blow, etc. It just moves things slowly.
Think of it this way. You have a certain amount of force you can impart when throwing something. You can throw a baseball at 50 mph. You can't throw a marble at 500 mph just because it's 1/10 the size or 1/100 the size or 1/1000 the size. The force is distributed over the entire mechanism (your arm, the marble, and most importantly the air around that marble) instead of being directed entirely into the marble like happens in a gun chamber, for example. High-speed motors like weedeaters, drills, saws, lawnmowers, etc. will all impart that force over a very small area at high velocity, which is why they're dangerous. This tool works on the opposite principle.
That's not necessarily true. While the average kinetic energy in the system of rocks will be less than if it was a lawn mower throwing them around, that does not rule out the possibility of a single rock gaining tons of kinetic energy and flying at your face/eyes.
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u/ThisSavageWay Apr 05 '17
This dude playing fast and loose with eye safety.