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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.
 

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As I mentioned previously, it would be confined like a mulch setup is.

As has also been mentioned, lasers don’t inherently zap through everything in their trajectory.
It's a fun intellectual exercise. It's just that fictional books and movies have given most everyone the wrong impression of what a laser actually does, or can do. Movies are likely the worst as it gives the impression that that single beam of light from a laser vaporizes or cuts through any material from the end of the weapon to some point miles away. The magnifying glass example I gave earlier is quite apt in working with lasers. The movie clip generously given by Sevenhills1952 is a prime visual example. The guy fabricobbled a 200 watt handheld "laser bazooka" but the focus point was around 18 inches from the end. Made a really nice spotlight, though.

With a laser, you are projecting a beam of concentrated single wavelength light. White light is what most all of us can perceive with our eyes and is between 400 to 700 nanometers. Although we humans can't see it, some other animals can see into the infrared or ultraviolet. Where the absolute focus endpoint is where the actual work is done. Anything before or after that focused endpoint is not affected. On metals, that focused endpoint is used to melt the metal. On wood or anything with soft tissue, that focused endpoint heats the water in each individual cell to make it "boil over" or "burn up" which is basically the same thing.

Now applying that to a conventional mower deck ain't gonna happen anytime soon. Almost all lasers are used in extremely clean and stable environments where dust, debris and vibration don't affect the focus.
 

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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.
 

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White light is what most all of us can perceive with our eyes and is between 400 to 700 nanometers.
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.
 

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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.

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Once upon a time someone decided to boil water by splitting atoms.

Personally I'm on the side of "simpler is better".
 

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Once upon a time someone decided to boil water by splitting atoms.
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.
 

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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.
 

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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.
 

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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. https://www.youtube.com/watch?v=r5vF6v29_Fc





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 didn't say I embrace the electric idea. My tractors are either diesel or gas, same with cars and trucks.
For just a riding mower to cut less than 2 acres battery power wouldn't be bad only if affordable and batteries last and not expensive to replace.

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With any application of Lasers to mow grass, you can bet that there will be unintended consequences. AND, so much for high-lift blades!
 

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I didn't say I embrace the electric idea. My tractors are either diesel or gas, same with cars and trucks.
For just a riding mower to cut less than 2 acres battery power wouldn't be bad only if affordable and batteries last and not expensive to replace.
No worries, I wasn't saying you did! :trink39:

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,,,
Balloons, paper, cardboard boxes, plastic if you're patient enough... great fun! But if anyone tries this or if they try to make a laser mower, DO put on laser safety glasses having the appropriate ratings for your laser (wavelength, intensity, etc) and please don't do it where the possibility exists of another person or a pet being hit by the beam. Even a cheap 1 watt laser will produce enough reflection off of a white wall to be blinding, and a direct reflection off of a shiny surface will cause eye damage.
 

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Looking a half century into the past, are we?



https://en.wikipedia.org/wiki/Elec-Trak
Electric cars have been around a century. Nothing new. What I'm saying is 50 years ago batteries weren't nearly as good as today. An all electric car going dead 100 miles from home is a problem. An electric riding mower 100 yards from home isn't.
I have a Toro battery powered push mower Grandad bought about half century ago.

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Some more learning moments.......

1st of all - Lasers do not need a lens to focus the beam. As was mentioned before, the very fundamental nature of what laser is that does not require a lens. if it does, it's not a laser.

The movie clip generously given by Sevenhills1952 is a prime visual example. The guy fabricobbled a 200 watt handheld "laser bazooka" but the focus point was around 18 inches from the end. Made a really nice spotlight, though.
Yea - he needed a lens because his multiple sources of laser light spread the power over a large emitting area. The lens was to bring the multiple laser beams into a single focus. If he had a real 500W laser, teh beam wouldn't be so broad, and therefore the lens would not be required. So he didnt have a laser. He had a laser array. Just like 10, 100hp engines is not the same as 1 1000hp engine. It's too bad he didnt have more advanced optics to "sum" the individual laser beams properly, into a single more-intense / powerful beam.

With a laser, you are projecting a beam of concentrated single wavelength light.
Not true. It depends on the type of laser.

Where the absolute focus endpoint is where the actual work is done. Anything before or after that focused endpoint is not affected.
Technically not true. The same work is done at any point of intercept. Especially since lasers don't have a focus point. But if you disperse the laser beam, still the same work is done at any point of intercept - the only difference is if the dispersion results in a larger area, then the total work is divided by that area - which may dilute the effectiveness of what you are trying to do with that beam, to a point of uselessness....

On wood or anything with soft tissue, that focused endpoint heats the water in each individual cell to make it "boil over" or "burn up" which is basically the same thing.
totally false. Water has nothing to do with laser etching of wood. And even if it did, boiling over of water is absolutely neither part of that process, nor is it the same as burning.
boiling of water = heating it up... no change chemically
burning = oxidizing... ie a chemical reacation...
and water doesnt burn... because water is already oxidized hydrogen. nothing left to oxidize. Burning of wood is the oxidation of hydrogen, carbon, and other elements that make up the pulp of the wood (celluluse, etc). And by the way, it does not at all matter if the wood tissue is soft, hard, cold, wet, happy or sad.... the oxidation reaction, or burning of wood is induced with the high localized temperature, and the presence of oxygen. If you tried to do this in a vaccuum, the heat would heat up the solid material (cellulose etc) and boil it (the actual cellulose) into its' gas-form, or even break it up into into smaller hydrocarbon molecules - depending on the intensity of the localized heat....

cheers...
 

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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.
 

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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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