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:
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.
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?