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I am trying to create a system of 2 3-sheave pulleys (along with terminal pulleys) that can hoist my hanging plants up to my rafters, such as here:

Hanging Plants Shaves

I am happy with my general design but what I am uncertain about is the design of the pulleys along the wall, the ones that redirect the forces right and then down.

I have designed a system with a 5/16" shoulder screw, 4 washers and 3 plastic sheaves 11/32" wide and 3/4" in diameter - I'll be using 1/4" jute as rope. (While the diagram shows that the sheaves are recessed near the centers in actuality they are flush across and will likely not rub with the washers in place.

Shave Setup

My question is is my pulley design good, or will the transverse forces likely warp, or snap, the screws (I have both stainless steel (40,000 PSI sheer strength) and alloy steel (86,000 PSI) available to me; which is best for pine and the forces here?)? These 5/16" shoulder screws have a 7/16" thread length and 1/4" thread width. The depth the screw penetrates the wood is also a factor I need to figure out - what is the deepest it needs go? The wood is pine. Each plant will weigh no more than 20 lbs; I figure not more than 100 N lift on each.

If this system does not work could there be a work around such as putting a cage around the pulleys?

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  • Delete and repeat questions make people upset - especially when they gave you ideas - rest assured I won’t make that error again.
    – Solar Mike
    Feb 22 '20 at 20:47
  • I repeated this question here because I tried twice on the Engineering board and didn't get a complete answer. The information you gave me was a good starting point but after working with it I realized it wasn't enough. I didn't have details such as the length of the shaft, the type of material, etc. You got me started but I needed more, does that make sense? Also, I deleted it from the Engineering board because folks kept voting down my questions without any explanation - it seemed to me it was a difficult board to work with. I asked you a second question there too but I got no answer. Feb 22 '20 at 22:07
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    Welcome Jesse, you have beautiful diagrams there. Although I cannot expertly answer your main question (an expert will be along shortly) I feel there is another consideration. As the cords enter and leave the pulleys that change the direction, make sure it doesn't chafe or rub on the edge of the pulley. Or the cord will fray and fail. Feb 22 '20 at 22:42
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    I am picturing the mounting hole in a 3/4" pulley and just don't think a hefty enough fastener would fit. Your system has no mechanical advantage, all the pulleys are just direction changes. The system will be subject to the weight of the load x 2 just to lift it + friction from multiple direction changes. You will need robust hardware with sturdy mounting. Feb 23 '20 at 23:09
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    hmm pine and a fairly light load, I'd reccomend they go at-least as far in as they stick out
    – Jasen
    Feb 24 '20 at 2:50

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