Years ago I wondered if a Laser beam with shields above and to the sides of it could cut grass instead of spinning blades. I think I mentioned it on another forum years ago but I don’t remember the answers. I honestly don’t know much about Lasers.
While it is theoretically possible, I doubt that any manufacturer would produce such a thing due to the potential for product liability lawsuits. A laser powerful enough to cut grass would be too dangerous. Consider the the laser pointer, which normally operates in the milliwatt range, and so cannot even cause paper to ignite, but it can cause permanent damage to the human retina. A laser powerful enough to cut grass at any speed that would make it competitive to spinning blades would easily cut through human flesh as well, and could easily be converted into a weapon.
Light Amplification by the Stimulated Emission of Radiation, or laser for short.
While applications for lasers have come up by leaps & bounds, I highly doubt we'll see them being used for rather mundane uses like cutting the grass on residential or commercial properties anytime in your children's children future.
Contrary to what one sees in movies, lasers work by focusing the light output onto a specific item. An easy way to think of it is to remember how you may have once used a magnifying glass to focus the sun's light onto a piece of paper (or other) to burn a hole. The point was to concentrate that intense focus point, too far away or too close didn't work. The same with lasers. There also can't be anything in the way of the beam because that will block the unfocused beam of light. Think of laser surgery where they have to insert a optic fiber to where the laser will work. They can't just aim the focus through your body.
The fictional popular "light saber" is not a laser, but a directed energy weapon that has a defined visible component, two quite different things.
That spinning blade stays within the confines of the mower deck (or is supposed to)....A laser beam goes forever. Just imagine, you are standing by your laser mower and the spinning beam hits your feet....."Look ma, I don't need shoes anymore"
Grass could be 'vaporized', so no clippings/thatch and completely enclosed cutting area.
No physical blade to encounter roots or other fixed objects.
No rotational momentum, so could stop instantly if field breeched.
No rotational force to throw rocks/objects.
Less potential for hazard in dry grass from sparks against objects.
The point was to concentrate that intense focus point, too far away or too close didn't work. The same with lasers. There also can't be anything in the way of the beam because that will block the unfocused beam of light.
Not the same. Lasers are "coherent" light. All (or nearly all) of the light energy is sent out in a single beam that doesn't need to be focused because it doesn't spread out as it travels away from the source. As to anything blocking the beam, if it is powerful enough to cut grass and the only thing in its path is grass, it will cut through any grass in its path given enough time.
Also remember that LASERs are use in surgery and all sorts of industrial applications, so the beam can be controlled and caught. It doesn't just continue on forever through other materials.
And of course, this is all casual conversation ... what if, type stuff. I don't ever expect to see it in practice.
My guess is practicality/cost/effectiveness, etc, all factored in make it not worth it. A laser pointer is about 5mW. In the US I believe 500mW is maximum you can own legally. A laser beam on police or aircraft can get jail time.
Here's a video of a young man who made a 200 Watt laser. It can pop balloons, burn wood, etc., but cutting grass at mower speed I bet would take more power.
Years ago Lowe's had a riding mower I thought of buying. Extremely innovative I thought. A gasoline engine with a generator and each of the three mower deck blades turned by an electric motor.
So no belts, and generator would run your house if you had a power outage!
A riding mower still needs propulsion, so the tried and true gas engine which also spins the blades makes the most sense.
We will certainly see 100% electric mowers in our future. Clean, quiet, simple.
Crap Cadet (MTD) already makes them, your choice of riding mower or lawn tractor. Personally I've no need or desire for an all-electric mower and definitely not an all-electric tractor whether it's a lawn tractor, garden tractor, subcompact, etc. I'll take a diesel please! However I can see the eco-hippie granola-munchers buying them and I would guess this is the target market for those machines.
Now as for lasers to cut grass. Lasers won't work if the optics aren't exactly aligned, so consider the environment under a running mower deck. You'd have vibration from the machine (unless it was electric) and wet grass would require much more power (or time) to cut because the surface temperature of each grass blade would not rise above 212 or so degrees until the water boiled away. Also remember that there are some people who can't even run a regular mower deck without damaging it on a regular basis, they run into rocks and fenceposts and everything else and I doubt the precision optics that lasers require would put up with that for very long.
I wasn’t thinking of a spinning Laser, but a fixed position one with shields on all sides accept the bottom.
I think those electric generator/mowers that were sold about 5 years ago had lots of problems and were discontinued.
My yard as I'm sure most people's yards aren't golf course is far from perfect. When I cut grass, types of grass and thickness varies, then I hit twigs, small limbs, leaves, etc. When I'm through it looks great.
A laser can't do that. It doesn't need to spin, but moving along at a constant speed it would have to be able to cut through all that variety of stuff. The sticks, twigs and leaves rather than getting chewed up (mulched) would be cut with precision which you wouldn't want.
I thought about laser years ago also...but it's just not practical.
Total electric you'll see with spinning blades. No gas or oil to fool with, plug it in overnight and you're ready to go. Quiet, very little maintenance.
Total electric you'll see with spinning blades. No gas or oil to fool with, plug it in overnight and you're ready to go. Quiet, very little maintenance.
Also remember that LASERs are use in surgery and all sorts of industrial applications, so the beam can be controlled and caught. It doesn't just continue on forever through other materials.
Yes, but in medical and commercial applications they are operated by trained skilled people. They are carefully aimed first, and then they are activated in short pulses only while they are properly aimed, so there is a very very low risk of them ever being activated while they are not aimed at an intended target. And yes, a laser will not continue on beyond something that blocks its path unless it can burn fully through the obstruction but again, in commercial and medical applications they are not turned on and left on to burn completely through the target, they are operated in short pulses to achieve the desired effect. In a lawn mower that uses lasers to cut the grass, it would not be guaranteed that it would be operated by a highly trained, much less highly skilled (hold my beer and watch this) operator, and it would not be guaranteed that it would only be operated in short pulses that would be reasonably guaranteed to only encounter blades of grass.
A bit off subject but an alternative way of cutting grass. Just buy some critters and graze it.
Advantages: no need for additional fertilizer, no fuel to buy, saved me about 30 hours of mowing time in one summer. May even do it again next year.
I realize not everone can do this but if the possibility is there its worth considering.
Man, you need a class in the physics of light. There is no such thing as "white light". The light that we perceive of as "white" is actually made up of all of the colors of the visible spectrum, as exhibited by a prism bending a ray of "white" light different amounts depending on the individual wavelengths producing a "rainbow" type effect. If what you said was true, "White light is what most all of us can perceive with our eyes", then we wouldn't be able to see colors.
I want blades to lift and mulch everything I mow. Even if you had the perfect laser system it would only work if the yard was flat, level, even, all the exact same grass, same grass blade sizes, etc. One leaf in the yard would be left behind looking like a piece of trash.
Golf courses use reel mowers because they cut like scissors. Multi-million dollar courses would have used lasers years ago.
That is exactly what happens in a nuclear reactor at a nuclear power plant. The boiling water then turns to steam which drives a turbine that spins a generator. Again, this is done by highly skilled people in a controlled environment, not by individuals in their home wishing to make a cup of coffee. Just like the medical and commercial lasers that have been discussed here are run buy highly skilled people in a controlled environment, not by a homeowner trying to cut their grass.
The gist of this thread was the OP was wondering why lasers haven't been designed for more mundane tasks such as cutting grass. Many of us have responded with either the complexity of doing that or attempting to explain what one sees in movies or reads in fictional books bears little relation to reality.
If one takes a look at the technological history of our species, they may find that in the periods of time where knowledge was tightly controlled by only a select few, it was a period of stagnation. Then an utter rank amateur with zero formal education or specialized training came along and changed it all.
It's a valid interesting idea. Perhaps a backyard tinkerer will read this thread and become inspired to solve the problem.
Are you all aware you can pull the blue-light laser from a dead Playstation 3 or blue-ray player, mount it in something like an old toy startrek phaser with some batteries a resistor,and a switch, and pop balloons with it? Think there's some youtube videos,,,
Although possible, I just don't see it as a practical option.
According to some research, a laser would need to have a strength of 450-465W, while metal only requires 300W to cut through thin sheet metal that is less than 2mm thick. A steel deck that is thicker than 2mm would be incredibly heavy. I suppose we could make the deck out of a different material, but there are not many alternatives. Additionally, a laser cuts by burning. Would burning the grass be that effective? Could it work? Yes. Would it work? Possibly. Does it make sense conceptually? Yes. Does it make sense safely or logically? No.
Yea.. agreed.... although I would go as far as to say that it does not even make sense conceptually Burning through grass to cut it?.. imagine the cutting swath... the laser will need to "sequentially" cut through all blades of grass that are between it, and the other edge of the deck. One instance, that may be 20 blades of grass... another instance it could be 100. So you have to design the laser to cut through all 100 to make sure you get an even cut.... (I can already imagine the flood of "I get un-cut strips with my laser mowing deck" threads on this forum). Each blade of grass is say 5mm wide. And say your mowing speed is 3kph (this is slow by mowing standards). That is 833mm per second. Which means the time a 5mm blade has the beam shining on it is: 6 miliseconds. That means your laser has to burn through 100 blades of grass in 0.006 of a second. That means each blade gets 60 microseconds of laser beam heat. The power required to achieve this will be in the "many kilowatts" range.
Then, imagine that as you move along, there are now only 20 blades of grass to cut... now you burn through them in 1 milisecond (simple math), and the remaining 5 miliseconds you are shining the "many kilowatts" laser at the other side of your deck. What happens next?
Then there is the other case... what if the blade of grass is turned sideways... now the blade is only 0.1mm long (on edge) and 5mm "thick" as far as far as the laser is concerned. And there are 100 of them....
See where this is going?
Why not just design grass via genetic modification, to grow only 2" tall?.... never need to cut again!!
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