Pulley / Fraying - "Mechanical Flower" Project

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Discussion Overview

The discussion revolves around a personal art project involving the mechanization of flower petals, specifically focusing on the challenges of ensuring the string mechanism operates continuously for an extended period without fraying or breaking. The conversation includes technical aspects of the setup, materials used, and potential engineering solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Chris describes the project goal of mechanizing flower petals using a braided fishing line and various tubing to minimize friction and wear.
  • Some participants suggest that the choice of materials and the setup may be overly complex, arguing that the fishing line should not fray under normal conditions if properly managed.
  • Concerns are raised about the need for adjustability in the string setup, with suggestions for alternatives like using a turnbuckle or a progressive spring to manage tension.
  • Participants discuss the importance of avoiding lateral motion of the string against surfaces to prevent failure, recommending the use of grommets and ensuring smooth transitions.
  • There is a suggestion to consider using shape-memory metal wires instead of string for a more reliable mechanism.
  • Chris expresses uncertainty about the sustainability of the current setup and seeks advice on potential failure points.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness and necessity of the current setup, with some suggesting simpler alternatives while others support the complexity of Chris's approach. The discussion remains unresolved regarding the best method to achieve the project's goals without string failure.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about material properties and the specific mechanics of the setup, as well as the lack of detailed visual evidence of the flower's movement.

Who May Find This Useful

Individuals interested in mechanical design, robotics, or art projects involving automation may find the discussion relevant.

  • #31
Howdy!
The Flexinol wire manufacturers don't have their own design...I've been looking online on how others have managed using the muscle wire and the hooking it up to the PC board, but still no luck ;( The snapping into shape is because there is too much current. Stilll tinkering ...

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  • #32
Fuichris said:
The snapping into shape is because there is too much current.
Are you sure about that? I haven't looked into Flexinol; I've been leaving that up to you. BioMetal, as I mentioned, has a hysteresis loop in its thermal cycle. At low temperatures, you can pull it to about 105% (or whatever disappointingly small percentage) of its normal length and it will stay there. When you heat it, it doesn't react at all until you hit its transition temperature (let's say 150° C as an example, but I really have no idea) at which point it spontaneously snaps back to its "resting" length within a millisecond or two. You can't deform it again until it drops to maybe 120° (again, just an example). I thought that since you had settled on Flexinol, it must be more controllable, but maybe it isn't. Does the literature state that it is, or did you just buy some to experiment with? If the latter, maybe what I was thinking of as the way to go with BioMetal is worth trying. Instead of what you're currently using as a return spring, (I would be using a leaf-type (no, not because you're making a flower, smartass...)) try one that perhaps has a more aggressive progression factor. I don't know whether or not that can be accomplished with a single leaf, or if you would have to go with multiple leaves like in a car suspension system. The bad aspect of that is that unless you have some very tiny shock absorbers in your parts bin, it will uncurl just as rapidly at it would curl without the spring. That would be okay if the flower that you want to model is a Venus flytrap, but your pictures sure don't indicate that. :p The whole issue is why I was hoping that the metallurgy had improved significantly since I dealt with it, so that a gradual transformation could be achieved. It's obvious from that one video that it's possible with some memory substance, but I don't know what it is.
Aw, nuts! Now I'm starting to think that my design won't work either. :(
I'll keep thinking on it.

edit: Actually, I'm currently too tired to keep thinking on it. Instead, I'll resume tomorrow (well, later today).
 
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  • #33
Hey now! I've been over-thinking this thing all along. Would a simple bimetallic strip such as from a thermostat work? Just heat the whole thing and let the differential reactions do the work...