Swivel Pulley Block with Bearing

thingiverse

After discovering the 608 bearing concepts that were out there, I wanted to put them into a situation where they could be tested in a real-world scenario - and a block seemed like a great starting point. This is a block like you see on sailboats, and is designed for 1/2 inch line. It's printed in 2 parts to enable the proper finishing of the different surfaces, which would not be possible if printed as a single piece. If you want to tinker the object itself (IE to swap out for different bearings, different shackle style, etc), you can find it at https://www.tinkercad.com/things/kxVOBi8siaG ## Designs There are three different designes that you can experiment with. All of them use the "Block Insert with Bearing" as the inner wheel, with different cases to contain that piece. Two of the designs split the Case into two separate objects. To allow for a flat, finished surface on both sides of the wheel, while still allowing for the printer to lay down material in a direction parallel to the load on the block, it was necessary to split the block into two pieces so that the sides could both be flat on the build plate. The Plate and the Body fit together with two angled pins at the top, and then the wheel provides a third point of connection between the two. The fit is intentionally quite snug which, combined with the layers of material on the pin and hole acting as ratchets against each other, makes the fit quite solid. - Block Insert with Bearing: The thing that spins, and is used for all Cases. This insert should be printed with raft so that the bottom bearing doesn't end up with a flat surface on the first layer(s) - if you don't use a raft, the bearing balls won't roll as well. It also does need support for the bottom center hole that accepts the case pin. - Block Split Case: A standard pulley block - Fiddle Block Split Case: A pulley with a pin to attach the end of your line, to allow for a 2- or 3-to-1 ratio. This one in particular needs a wall width of at least 3-4 to allow the cap on the pin to be securely attached. - Swivel Block Case: If you would prefer to print the case in a single piece, you can print this with raft and supports at a 45-degree angle. This allows the walls to be printed in smooth, flat surfaces - but it also means that the strength of the block is dependant on the strength of your layer adhesion - I found this to be weaker than when it was printed flat, but the large overhang on this if it were printed flat is extremely rough and catches on the block when it spins. ### Strength The strength is very much dependent on how it's printed. - With the NarrowShackle shell version and 1.2mm (3 layers) shell thickness in PLA, the shackle failed at just over 70 pounds of force (other layers around the shackle began delaminating and bending at about 50 pounds - but were not catastrophic failures). - With the ThickShackle shell version and 1.2mm (3 layers) shell thickness in PLA, one of the inner walls inside the bearing failed at just over 90 pounds of force (which in turn caused the side wall of the shell to fail after the bearing connection was no longer supporting the load). If you use more layers in the shell, use the Narrow vs ThickShackle shell versions, use different materials, or potentially even different temperatures (that impact layer adhesion), you may see different performance under load. Beyond structural failures, the bearing balls will begin deforming under load as well (especially if the block is static and not rolling), so use with a load is at your own risk and I encourage you to test in controlled situations with your specific printing setup. I recommend using a 3d infill, as 2d will create weak points between the fill paths. As before, the more infill, the stronger the block will be (though to a much lesser extent than the impact from more shell layers)