Ok, I think we should get off the topic of lasers here - although that would remove any shred of 'electornics' which is what this forum is all about
In terms of a problem to be solved - altohugh I am no expert in tree-felling, or landscaping - but started a fire at say... a foot from the top, will not cause that top foot to drop. As many have mentioned, getting it to a point where it sustains burning is difficult laser, or no laser, and as heat generally travels upwards
<tangent> When wood is heated it releases 'wood gas' which burns, the actual wood itself merely gets heated, the gas is flamable, combusts, creates heat, so it rises, heating the wood above it, when releases more 'wood gas' etc.. etc..if wood burnt directly, there would be no jets of flames coming from embers, or flames at all for that matter</tangent>
So I can see the logic behind this, and perhaps EVEN the idea of using a laser because its about creating a focused point of ignition at a distance that is difficult to get to (you wouldn't get me up a 50 foot ladder leaning against a wobbly tree). But my last words on this is that
a) would require a very powerful continuous beam laser. I am unaware of any solid state device capable of the 100W+ needed to do this that can be focused any further than a few inches. CO2 lasers are IR, used for welding. They are invisible, difficult to focus far, so aiming it and adjusting the optics would cost far more than hiring someone to chop it up bit by bit. Visible lasers just don't have the power, except perhaps a 100W argon (that's again, 20x than hiring out an entire of team of guys to do this). Any other form of laser is generally pulsed. A Nd:YAG lasers often boasts kW power - but pulsed so the average power (required for continuous heating of poor conductors of heat ie: wood) is too low.
a) *ammendum* just because a 5W laser can set fire to a bit of paper, doesn't mean to say it'll do it to wood. The target needs to absorb as much energy from the beam as possible. Not to mention tinder, kindling, all of hich would need to be stuffed in a hole dirlled in the tree - so you woudl HAVE to go up there anyway.
b) Burning the pole/tree in stages, starting at the bottom of a top section would simply leave you with a very sturdy lump of charcoal, which would spit embers around everywhere as it burnt, creating fires here there and everywhere.
c) You will have to accept that it is either going to cost you to hire out someone to do it for you. Hire out your own equipment and risk injury, or just wait for it to fall on something expensive.
d) If you're really after the cheapest option, which involves more time and effort than money - befriend someone who has experience in this, and owns a chainsaw. Do HIM a favour, and he might help you out.
If you manage to do this with a laser, cheap or otherwise, without harming anyone I will personally go over there and buy you a beer. Nice idea, but impractical. If you really want to see what happens, then why not buy a 20-30W laser off ebay? calculate the optics needed (all lasers have divergance, how small that is just depends on how accurate the optics are). It'll cost you >$100, and you'll be disappointed.
I do not in any way mean to discourage brainstorming and idea's, thinking is good, but the reaction from others was one to bring you back down to earth :/
In terms of a problem to be solved - altohugh I am no expert in tree-felling, or landscaping - but started a fire at say... a foot from the top, will not cause that top foot to drop. As many have mentioned, getting it to a point where it sustains burning is difficult laser, or no laser, and as heat generally travels upwards
<tangent> When wood is heated it releases 'wood gas' which burns, the actual wood itself merely gets heated, the gas is flamable, combusts, creates heat, so it rises, heating the wood above it, when releases more 'wood gas' etc.. etc..if wood burnt directly, there would be no jets of flames coming from embers, or flames at all for that matter</tangent>
So I can see the logic behind this, and perhaps EVEN the idea of using a laser because its about creating a focused point of ignition at a distance that is difficult to get to (you wouldn't get me up a 50 foot ladder leaning against a wobbly tree). But my last words on this is that
a) would require a very powerful continuous beam laser. I am unaware of any solid state device capable of the 100W+ needed to do this that can be focused any further than a few inches. CO2 lasers are IR, used for welding. They are invisible, difficult to focus far, so aiming it and adjusting the optics would cost far more than hiring someone to chop it up bit by bit. Visible lasers just don't have the power, except perhaps a 100W argon (that's again, 20x than hiring out an entire of team of guys to do this). Any other form of laser is generally pulsed. A Nd:YAG lasers often boasts kW power - but pulsed so the average power (required for continuous heating of poor conductors of heat ie: wood) is too low.
a) *ammendum* just because a 5W laser can set fire to a bit of paper, doesn't mean to say it'll do it to wood. The target needs to absorb as much energy from the beam as possible. Not to mention tinder, kindling, all of hich would need to be stuffed in a hole dirlled in the tree - so you woudl HAVE to go up there anyway.
b) Burning the pole/tree in stages, starting at the bottom of a top section would simply leave you with a very sturdy lump of charcoal, which would spit embers around everywhere as it burnt, creating fires here there and everywhere.
c) You will have to accept that it is either going to cost you to hire out someone to do it for you. Hire out your own equipment and risk injury, or just wait for it to fall on something expensive.
d) If you're really after the cheapest option, which involves more time and effort than money - befriend someone who has experience in this, and owns a chainsaw. Do HIM a favour, and he might help you out.
If you manage to do this with a laser, cheap or otherwise, without harming anyone I will personally go over there and buy you a beer. Nice idea, but impractical. If you really want to see what happens, then why not buy a 20-30W laser off ebay? calculate the optics needed (all lasers have divergance, how small that is just depends on how accurate the optics are). It'll cost you >$100, and you'll be disappointed.
I do not in any way mean to discourage brainstorming and idea's, thinking is good, but the reaction from others was one to bring you back down to earth :/