Testing of a drive method for 3D printer with spectra line.
Grooves in drive pulley are parallel as is the idler roller grooves, the idea is that the angle of line going to the drive will never change no matter where how far its "wound" up.
Normally if just wrap the pulley it will act like a screw and cause the line to climb or lower on the pulley.
I did not get any photos of it but I did also try crossing the wraps between the drive and idler roller to slightly boost the contact area on the drive pulley but gained no reduction in the gradual error.

This failed because no matter the number of turns or line tension I would still have a slow gradual loss of position during printing.

However i'm still posting this as it could still be useful for a camera slide or linear motion system where perfect repeatable position is not needed.

STL files are mostly for reference, idler side had a bolt and a bearing on the top and bottom.

Video of the motion: https://youtu.be/9TBoSpT2unQ

Inspired by this Rob Povey's blog:
http://3dprinterhell.blogspot.com/2013/06/a-better-filament-drive.html?m=1

Also a video by Rikard Hamrin
youtube.com/watch?v=pKerL-opsj4