Universal Bottom Bracket Adapter

thingiverse

This is a configurable/parametric model for an adapter to convert one type of bottom bracket tool to another. The concept is based on rzschokke's SRAM DUM 44 to 49mm design as this seemed like a good way to make a plastic bottom bracket socket without concentrating forces on the four sides of a 1/2" square drive or six sides of a hex socket. I decided to build this in OpenSCAD to allow for different versions of the adapter to be built to support many combinations of existing sockets/tools and bottom brackets. The parameters define settings for the socket that interfaces with your bottom bracket and a plug that would interface with an existing bottom bracket tool of another size you want to adapt. Here is a description of the parameters: * socket_ID: Inner diameter of the socket that will fit over the bottom bracket. You will likely need to increase this diameter by 0.2-0.4 mm as printed circles tend to come out slightly smaller than defined in the model. * socket_splines: number of splines (notches) on the bottom bracket socket * socket_spline_diameter: diameter of the socket splines in mm * socket_spline_offset: This moves the splines in or out from the inner diameter of the socket. A value of zero places the center of the spine on the socket wall. a positive value pushes the spline out so that less of the spline protrudes into the socket. * socket_wall_thickness: thickness of the socket wall in mm * socket_depth: depth of the socket in mm * min_socket_bottom: height of the cone connecting the plug outer diameter to socket outer diameter when the socket OD is less than or equal to the plug OD * transition angle: limits the overhang caused by having a larger socket outer diameter than plug inner diameter. This angle is used to calculate the height of a cylindrical cone that connects the outer diameter of the plug to the outer diamter of the socket ONLY when the socket OD is greater than the plug OD. If the socket OD is less than or equal to the plug OD min_socket_bottom is used instead. * plug_OD: outer diameter of the plug in mm that will fit the existing tool you have * plug_splines: number of splines/notches for the tool you have * plug_spline_diameter: in mm * plug_spline_offset: see socket_spline_offset but think plug side * plug_depth: in mm * plug_hole_ID: some bottom bracket tools like the Wheels double-sided 48-16/44-16 I have need a recess to clear the 1/2" drive interface For my own purposes, I needed to install a Race Face Cinch 30 mm bottom bracket I had on hand. This uses a 46mm 12 notch tool (Park Tools BBT-79) which I did not have on hand. I did have a Wheels 48 mm 16 notch socket. I was able to torque to 40 Nm with PETG without issue. I ran out of blue filament and snuck some black in during my print. I used the following parameters to make an adapter: * socket_ID: 46.4 (for 46 mm OD BB) * socket_splines: 12 * socket_spline_diameter: 2 (I had to guess here as I was working backward from my Race Face bottom bracket) * socket_spline_offset: 0 * socket wall thickness: 4 (I like big walls and I cannot lie) * socket_depth: 8 (This was a bit more than I needed. My bottom bracket notches were only about 5.5 mm deep) * min_socket_depth: 0 (not used as my socket OD exceeds plug OD) t* ransition_angle: 50 (printed nice) * plug_OD: 49 (it's labeled 48. The Wheels website says 48.5. I measured my old Wheels BB outer cup and got 49.1 mm. Printing at 49 was perfect.) * plug_splines: 16 * plug_spline_diameter: 6 * plug_spline_offset: 1.5 (Less than half a notch is visible on the BB cup. I came up with 1.5 after some trial and error and together with the 49 plug_OD I eneded up with a great fit) * plug_depth: 6 (The Wheels socket depth is a little over 7 mm but I figured this was good enough) * plug_hole_ID: 22.4 (A bit more than the measured OD of 21.5 for the 1/2" drive interface. Remember it prints smaller.) I'm hoping others with a need for another adapter will add comments for what worked for them. I'll try and add shared details to the description to make it easier to find settings you need. PRO TIP: when testing out new settings add the model twice with one copy inverted. Print the first 4 or so layers and cancel the print. This will make it easy to test the fit of each component in your adapter.