With luck I can place everything under the change gear cover. Use ball bearings where needed so nothing under the cover will need oiling. Make it an oil free zone if that is possible.
Starting on the encoder end. Plan is to replace the existing spur gear on the end of the spindle that drives the existing change gears. It is 54mm in diameter.
circumference = pi * diameter = 3.14 * 54 = 169.56 mm
Am approximating here so call it 170 mm.
circumference / pitch = number of teeth
The GT2 2mm pitch is 2mm.
170 / 2 = 85 teeth
Pulles were generated with a openSCAD script found on thingiverse. I patched the script to make keyways with a code fragment provided in the comments by abratjason
Parametric Pulley with multiple belt profiles
by droftarts January 2012
Both the .scad and .stl files are located on a shared folder on My Google Drive.
I settled on 80 teeth. It is a little smaller but a metal 80 tooth pulley maybe easier to find if I need to go that route.
This picture was taken to help me visualize the mounting the decoder. If you look carefully you can see the black 80 tooth pulley The large hole to the lower right of the spindle will be the pivot for an arm holding the decode.
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Also printed the silver pulley for the encoder. I keep calling these gears because they look like a gear. Sadly the 6mm hole in the center printed a bit small. I should have expected that and printed a series of low layer count trials to get the fit. Maybe a 6mm drill bit. Maybe reprint. I also used 2 set screw at 180 degrees to reduce distortion. Not sure if that was good. Ah well can always use one.
The back pulley under encoder pulley is an example of what printing with non dry PLA looks like more on that later. This was printed from the .stl on ThingiVerse.
It looks like the stripe with the circle is an shallow alignment key. It is not well define on this effort so if I use it it will be filed flat.
