h a l f b a k e r yWhat's a nice idea like yours doing in a place like this?
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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.
Some not-ok lumberjacks.
https://www.youtube...watch?v=JHZkR6UVegY
[mylodon, Nov 21 2017]
Inspired by:
hoop_20chainsaw
[MaxwellBuchanan, Nov 21 2017]
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Yes, but if nobody is there listening .... |
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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. |
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But after then it might be quiet. |
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Ah, you might have been included in our alpha test programme, [mylo]. |
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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. |
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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. |
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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. |
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Either way, this would be one of the most
spectacularly dangerous pieces of equipment ever
devised so, [+] |
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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. |
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As for the necessary power - all that's needed is a modest electric motor and some huge amount of gearing. |
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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. |
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Anyway, I'm thinking the Monty Python routine sort
of killed the "tree surgeon"'s desire to brag about
being a lumber jack. |
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" As for the necessary power - all that's needed is a modest electric motor and some huge amount of gearing.
— MaxwellBuchanan, Nov 21 2017 " |
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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. |
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" Most mind numbingly dangerous job you can imagine.
— doctorremulac3, Nov 21 2017 " |
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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. |
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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. |
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OK, I'll try to do the maths. |
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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). |
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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. |
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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). |
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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 |
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So, there you have it. A 5HP motor, drastically geared down, ought to be able to fell a 1m tree in 10 minutes. |
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//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.// |
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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. |
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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. |
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Here's my advice if it does work: Don't sell these
things, lease them like the inventor of the oil drill
head
did. |
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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? |
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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. |
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No, wait; is any part of this thing meant to rest on the ground in
the first place? |
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Nope. You tie it to the tree like an evil belt, and then let it go to work. |
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It would also make a great murder weapon for a horror movie. |
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<shakes magic eight-ball>
{It Is Deciduously So} |
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So, you're not just taking the pith then. |
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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? |
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Also, regarding the wedge, doesn't the phrase "unstable
equilibrium" spring to mind? |
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For 750kN you'd need a significantly more sturdy cable.
1.5 inches or say 1.75 inches for a reasonable margin of
safety. |
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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. |
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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. |
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Cased in cotton, it could be quite quiet. |
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I'm pretty sure a noose qualifies as a loop, thus indicating
this Idea has an inaccurate title. |
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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. |
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Not if a sensor determines width of the band and shuts down automatically once a certain width has been become narrower than. |
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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. |
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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" |
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//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. |
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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. |
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//at risk of pivoting, on that edge, either up or down.// |
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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. |
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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. |
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Which failure mode would you like to explore first? |
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Pah. We shall simply fix it in software. |
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... as they said about the F-35, repeatedly. |
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