Schacht Bobbins

This design makes it easy to print bobbins for Schacht spinning wheels (Matchless, Ladybug, FlatIron - I believe the Reeves uses a different design though). 

I designed this with the following goals:

• Support both the standard and high-speed ratios
• No supports or overhangs over 40-degrees
• Glued attachment (I print these in ABS and use acetone to weld the pieces) for robustness and durability
• Optional 608 bearing design. The Schacht flyer uses an 8mm shaft, which pairs nicely with standard 608 bearings (~$0.50 ea) and gives you a practically silent bobbin, even at high speeds with eccentric loading.

I suggest printing, assembling on the flyer, then spinning a bit to make sure the ends are centered. If you push the end onto the shaft the layer lines will “lock” loosely, allowing you to spin the assembled bobbin. Once you're happy with the balance, apply a tiny bit of glue / acetone to the joint and let it try before removing from the flyer.

If you choose to print the no-bearing version, you'll need to use a 5/16" (or 8mm) drill bit to ream out the hole, and probably some fine-grained sandpaper to open it out more. The goal is for the hole to be as snug as possible without preventing the bobbin from spinning freely if you give it a spin.

This design incorporates lessons from several other designs, which I'm grateful to have had access too:

• https://www.thingiverse.com/thing:2122000 stays very true to the Schacht bobbin design, but I found that the attachement was loose and hard to center
• https://www.thingiverse.com/thing:2638750 Uses the end caps for the “bearing” surface which is nice, however I find 3d-printed threads to be finnicky and wanted something simpler
• https://www.thingiverse.com/thing:5611286 Uses a clever snap-ring attachment combined with a tapered, hexagonal connection point. I wanted to print a high-speed bobbin though, and the central shaft was too large to accommodate the smaller diameter of the high-speed drum.
• https://www.akerworks.com/collections/flat-pack-bobbins/products/flat-pack-bobbin-schacht-systems I didn't want to try to replicate the connection mechanism, but I liked how  the support ribs and the drive band groove are visually integrated.

You can see several iterations of the design in one of the pictures. Lessons learned along the way:
 

1. Overhangs too steep initially. Also, the inner spokes added a ton of print time for not much benefits
2. The simplified top piece printed much better, but the deep bevel made it difficult to oil during use.
3. Adopted Schacht's design for the end - making a small lip. This leaves space for the oil tip, and minimizes the surface area touching the whorl. I also changed from a circular arc to a logarithmic spiral for the webbing - I like it visually and it uses less material.