Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Calibration Device

by WheresWaldo Dec 30, 2018
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I've thinking about something like this for a while, thank you for publishing your design. I'm wondering if your worried that drilling the 2020 extrusion will weaken it too much to handle the pulling forces? If an assembly guide is not coming some close ups, of the drilled sections and spoke retention in particular, would be nice.

I need to do a write up, right now I am working on another version that uses 3030 extrusion. With regard to using 2020, I saw no ill affects drilling out the 2020. It is just an 8 mm hole in each end and what I did was 3D print filler pieces that were inserted on all four sides of the extrusion before drilling. That was enough to strengthen the extrusion, but I don't think it really needed it. The spoke attachment at the top end (hook end of the spoke) is a flat thumbscrew like this offered by McMaster-Carr (https://www.mcmaster.com/90359a180). the other end is a 4 mm hole drilled though an 8 mm acorn nut so that a spoke nipple could be inserted into the nut before screwing it on to the end of the 8 mm threaded rod.

Unfortunately I cannot take any more pictures of this rig since I have given it to my nephew and it is no longer in my possession. I will try to answer any questions, posted in the comments or in the bike group here on Thingiverse.

The new version I am working on is bigger and I am using 12 mm brass bolts drilled with a #51 bit then tapped with a #2-56 UNF tap so a spoke can be directly threaded into the end. This one will use a load cell and a digital readout. I am going to use an 8 mm lead screw instead of the threaded rod to make adjustment easier. But it basically looks just like this one only it's older brother.