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I would like to transfer horizontal swaying movement of a tree into oscillating vertical movement. How to do it? It does not have to be ideal perpendicularity or straightness. More or less efficient mechanism.

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Update. More details on measures. I present also a solution I was thinking. A bar attached to a tree with a pivot point in the middle. I have not tested it yet. Anyway I got some doubts about behavior of the bar.

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    $\begingroup$ You might be interested in ncbi.nlm.nih.gov/pmc/articles/PMC3231266. Have a look at the conclusion. They're talking mW. $\endgroup$
    – Transistor
    Apr 7, 2022 at 21:57
  • $\begingroup$ put two different sized wheels that are attached to one another. Wrap the rope attached to a fixed object around the small wheel. Wrap a rope attached to the object you want to go up and down around the large wheel. Set the moving object to mid height when the tree is in its resting position. If you need to eliminate the horizontal movement from the moving object, either put it in a vertical guide way, or pass the rope through a hole or pulley in a fixed point above the moving object. $\endgroup$
    – Forward Ed
    Apr 11, 2022 at 21:48
  • $\begingroup$ Note the object will have to be heavy enough to overcome friction in the system, yet light enough to allow the tree to sway. $\endgroup$
    – Forward Ed
    Apr 11, 2022 at 21:48
  • $\begingroup$ IF you have a nearby fix position above ground, just place a pulley at the fixed position to change the direction of the rope. $\endgroup$
    – Forward Ed
    Apr 11, 2022 at 21:50
  • $\begingroup$ @ForwardEd Can you please make a sketch of your wheels system. There is no one way of joining two wheels. $\endgroup$ Apr 12, 2022 at 12:01

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Following up on the comment by @ForwardEd, I too believe the use of a pulley is benefitial to your problem, especially considering its excellent ability to change the direction of a force. In the below image, two possible setups are visualized using pulleys.

For the following scenarios multiple simplifications are made, seeing as they are all dependent on your objective (e.g., how heavy is the object to be lifted and how long should it last?), your budget (what can you afford in terms of material) and more. Examples of what is not considerd is the effects introduced by the catenary curve of the rope or the elasticity of the rope.

In the first scenario, which is also the most ideal one, we assume you have access to a (more or less) rigid structure, e.g., a wall or a larger tree (with lower sway motion given an equal load). You may then attach the pulley to the rigid structure in the same height as the rope is attached to the tree, giving an equal amplitude of the bottom part of the rope and the sway of the tree.

In the second scenario, it is assumed that tree is standing by itself. If connecting the rope with a pulley placed at the ground, the result is similar to scenario 1. However, since the sway motion of the tree now has to be decomposed to the direction of the rope, a sway motion of 1m will not result in a 1m change in the rope. How much is lost is dependent on the distance from the tree to the pulley, and can be computed using e.g. the Pythagorean theorem (but keep in mind that we then assume a rope with no stretch or catenary curve, which in reality will dominate as the distance becomes large). To redirect the motion of the ground pulley as vertical, I have chosen to visualize a possibility where another pulley attached to a smaller structure is used, but here there are many possible options.

Two possible setups for use of pulleys

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No matter what you do, you will need a second body for your tree to move relative to. You could be using the earth as in your rope example. It is also possible to use a mass in the tree, much like a magnet in those shake and recharge coils, although I do not recommend it.

I do however suggest use of hydraulics over the pulley. Although one might think the losses would be greater, it really all depends on a lot of factors such as what the end goal of the energy truly is. If efficiency is the goal and wind is moving the tree, you would likely fare better in going after the wind!

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Lever pivot mech

P is a pivot, A and B are connected as shown. Movement in the horizontal plane via A is converted to movement in the vertical via B. There will be sinusoidal considerations if the movement is excessive, otherwise it is linear for small values of movement.

This is a general response to a general request. More specific configurations could be created for more specific conditions.

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  • $\begingroup$ Thank you. I edited my answer to provide more details. Tree is about 10 meters high. Sway amplitude 0.5-1 m. Your blue crane should be be relatively small one, otherwise it will not be practical. $\endgroup$ Apr 7, 2022 at 22:24

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