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Loop no-chain saw

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I'm not a lumberjack (even though I'm okay). Howevertheless, this is a lumberjacking idea.

The problem is how to bring down a tree quickly and easily and, incidentally, quietly.

What we have, to solve this problem, is a length of 1/4" steel rope. One end of the rope is fixed to the motor unit (more on this later), the other end is free.

Wrap the rope once around the tree, so that it forms a loop that returns to the motor unit. The free end of the rope is then feed into a spindle which is driven, slowly but very powerfully, by a motor.

So, now you have a loop of steel rope around the tree, fixed at both ends to the motor unit. The motor unit itself has a steel wedge between the points where the rope enters and leaves it.

You now turn on the motor unit and, very very slowly and forcefully, it tightens the steel rope, cutting or crushing its way through the trunk. As it does so, the wedge naturally pushes the trunk to one side, so that it will fall predictably. As the steel noose tightens to almost nothing, the tree falls.

MaxwellBuchanan, Nov 21 2017

Some not-ok lumberjacks. https://www.youtube...watch?v=JHZkR6UVegY
[mylodon, Nov 21 2017]

Inspired by: hoop_20chainsaw
[MaxwellBuchanan, Nov 21 2017]

[link]






       Yes, but if nobody is there listening ....
normzone, Nov 21 2017
  

       But if someone was there - it would not be quiet. You'd still need some loud two-stroke motor. There would be a lot of screaming and yelling; as the wire cuts towards the motor creating a hinge that levers two million pounds of tree over the operator and the motor; pinching the wire and the wedge, locking the machine into place as the wire cuts erratically through rot and heartwood, twisting the trunk even as the operator tries to run away; as branches splinter and trunks shatter and the tree drops down onto the ground, slamming the operator deep into wet moss and decayed forest loam, burying the mistake forever.   

       But after then it might be quiet.
mylodon, Nov 21 2017
  

       Ah, you might have been included in our alpha test programme, [mylo].
MaxwellBuchanan, Nov 21 2017
  

       Great idea, if you use a chain with blades on it instead of a steel rope (I think they call those cables) and then have the pointy bits equipped cable turn, like a chainsaw. But looping the chain around the tree and pulling the loop closed seems like a really cool idea.   

       You're talking about is crushing your way through the tree though. It could be done but I'm pretty sure the engine you'd need to pull that cable through the tree like a wire through butter would be anything but quiet.   

       Now if you had the whole loop spinning (like a chainsaw) as it shrunk, this would make sense. A relatively small motor could do the job.   

       Either way, this would be one of the most spectacularly dangerous pieces of equipment ever devised so, [+]
doctorremulac3, Nov 21 2017
  

       The linked idea, which inspired this one, had a looping chainsaw belt but the annotations identified some flaws in the idea, mainly to do with the chain getting pinched.   

       As for the necessary power - all that's needed is a modest electric motor and some huge amount of gearing.
MaxwellBuchanan, Nov 21 2017
  

       I'll bun that one too.   

       I actually WAS a lumberjack. You may ask "Why didn't you say so earlier?". Must have slipped my mind. I cut down trees one summer in my youth. Most mind numbingly dangerous job you can imagine.   

       Anyway, I'm thinking the Monty Python routine sort of killed the "tree surgeon"'s desire to brag about being a lumber jack.
doctorremulac3, Nov 21 2017
  

       " As for the necessary power - all that's needed is a modest electric motor and some huge amount of gearing. — MaxwellBuchanan, Nov 21 2017 "   

       I don't know about that - if I was an electric motor and was responsible for doing all that I think I'd be pretty upfront about wanting full credit for it, plus any perks like groupies and product endorsements.   

       " Most mind numbingly dangerous job you can imagine. — doctorremulac3, Nov 21 2017 "   

       I've heard tell of somewhere back in my family tree there was a relative who was a topper, who's luck ran out one day.   

       I have sat on a branch and cut it off with a chainsaw while a friend drove the truck that was attached to the rope that dropped the branch where I wanted it. Textbook perfect outcome - if a crazy man had written the textbook and was willing to do stupid things for money.
normzone, Nov 21 2017
  

       OK, I'll try to do the maths.   

       An axe with a dull edge - say 500 microns thick, will penetrate some way into wood - say 5mm. Assume that the axe head weighs 1kg, the blade length is 100mm, and the swing speed is 5m/s (all reasonable guesstimates).   

       So 1kg of blade is decelerating from 5m/s to 0m/s over a distance of 5mm, which will take it 2ms. Hence, the deceleration is about 2500m/s/s. Since F=ma, the force applied by the axe's (blunt) edge is about 2500N.   

       Now suppose our cable is 5mm in diameter (and, for simplicity, ignore the fact that the cross-section is round), and 3m long (wrapped around a 1m diameter trunk). It therefore has 3000 x 5 = 15000mm2 of contact area, as compared the the dull axe's edge of about 50mm2- i.e., about 300 times greater contact area. So, it will have to provide a force of about 300 x 2500N, or about 750,000N (75,000 kg force).   

       The motor has to pull the cable for a total of about 3 metres (to close the loop), so the total energy involved is force x distance = 2.25MJ. Let's assume we're prepared to wait 10 minutes for this to happen; that equates to 3.75kW of power, or 5HP   

       So, there you have it. A 5HP motor, drastically geared down, ought to be able to fell a 1m tree in 10 minutes.
MaxwellBuchanan, Nov 21 2017
  

       //I've heard tell of somewhere back in my family tree there was a relative who was a topper, who's luck ran out one day.//   

       He was a brave man. The chainsaws these guys use do something called "kickback" if they're not careful. Heard some pretty gory stories from my former employer.   

       Well Max, if your numbers are right, this has revolutionized logging and you need to get this thing patented because you're a very rich man if this works.   

       And hey, it might.   

       Here's my advice if it does work: Don't sell these things, lease them like the inventor of the oil drill head did.
doctorremulac3, Nov 21 2017
  

       Well, as long as I can get the HB site taken down, shoot anyone who may have read this, and claim I never posted the idea, a patent would be a great idea. Now, who do I know who's read this?
MaxwellBuchanan, Nov 21 2017
  

       The machine is not quite so heavy, nor so firmly anchored to the ground, as the tree. And, because of roots, the ground next to the tree is never quite level. And, since it's garrotting rather than sawing, there will probably be an early step in the process in which, embracing the tree, it climbs a few inches up it like a satanic koala. It's only at this point that the final orientation of the wedge is settled.   

       No, wait; is any part of this thing meant to rest on the ground in the first place?
pertinax, Nov 21 2017
  

       Nope. You tie it to the tree like an evil belt, and then let it go to work.   

       It would also make a great murder weapon for a horror movie.
MaxwellBuchanan, Nov 21 2017
  

       <shakes magic eight-ball>
{It Is Deciduously So}
  

       So, you're not just taking the pith then.   

       So, with the 5hp engine, plus massive gearing, all engineered to be less crushable than pressurised hardwood, how much does the evil belt buckle weigh, that you're going to be positioning by hand?   

       Mind your fingers.
pertinax, Nov 21 2017
  

       Also, regarding the wedge, doesn't the phrase "unstable equilibrium" spring to mind?
pertinax, Nov 21 2017
  

       For 750kN you'd need a significantly more sturdy cable. 1.5 inches or say 1.75 inches for a reasonable margin of safety.   

       That will give you about 105,000mm2 contact area, 2100x the axe. That gives about 5.25 million Newtons of force, sadly, that will require a thicker cable.   

       I worked out that a simple swap in materials is all that is required. Instead of steel, a mix of polymers and RDX, say some C4. That supplies significant horsepower and tree felling power all in one.
bs0u0155, Nov 21 2017
  

       Cased in cotton, it could be quite quiet.
mylodon, Nov 21 2017
  

       I'm pretty sure a noose qualifies as a loop, thus indicating this Idea has an inaccurate title.
Vernon, Nov 27 2017
  

       How so?
MaxwellBuchanan, Nov 27 2017
  

       That thing is going to get a certain distance into the tree and then blast out the last bit in a spray of wooden shrapnel.
nomocrow, Nov 27 2017
  

       Not if a sensor determines width of the band and shuts down automatically once a certain width has been become narrower than.   

       I still think the wedge is going to twist around under tension until it's flat-side-on to the tree, thereby failing to dig into the wood and failing to push the trunk "naturally" to one side.
pertinax, Nov 27 2017
  

       Would the famous song become: "Oh I'm a loopyjack and I'm ok"?
You would also need to be careful that the idea didn't modify itself into a new title: "Look no-brain saw"
xenzag, Nov 27 2017
  

       //the wedge is going to twist around under tension// Hmm. Possible. So, what's needed is for the gearing to pull equally on both ends of the loop, which should be doable.
MaxwellBuchanan, Nov 27 2017
  

       But you're fixing the wrong dimension. The wedge, which is initially just resting its edgy part horizontally on the outside of the bark, is at risk of pivoting, on that edge, either up or down. I don't think equalising the sideways pulls will fix that.
pertinax, Nov 28 2017
  

       //at risk of pivoting, on that edge, either up or down.//   

       Ah, I see what you mean. Well, in that case, give the wedge "wings" that extend above and below to stop it tilting, until it has enough bite to be stable.
MaxwellBuchanan, Nov 28 2017
  

       Excellent. Now we have lofty wing, nether wing and beak. If the wings are rigid, then they will disperse the pressure that was supposed to be exerted through the beak, rendering it figuratively bootless and straining the metaphor to its breaking point. If they're not rigid then, when the tension is cranked up, they will restrain and balance the wedgy beak about as effectively as Nick Clegg restrained David Cameron.   

       Which failure mode would you like to explore first?
pertinax, Nov 28 2017
  

       Pah. We shall simply fix it in software.
MaxwellBuchanan, Nov 28 2017
  

       ... as they said about the F-35, repeatedly.
pertinax, Nov 29 2017
  
      
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