Summary

Even when dropped all the way, a few millimeters of my dropper seatpost stanchion is still showing. This makes the perfect place to clamp on a collar so that I could attach other things to my seatpost.

This is the collar that I made to mount a Cycliq Fly6 tail light to, but I also added a lip to it so seat pack straps don't slide down onto the stanchion.

The seatpost is a Brand-X Ascend II 27.2mm dropper with a stanchion diameter of about 21.8mm. This is probably also compatible with other dropper posts such as a PDW 27.2mm. The clamping height is 4.5mm, so you want to make sure you have that much stanchion showing at full drop otherwise the top seal will get crushed.

Other parts needed are two M3x8+mm screws (socket or pan head- probably anything will work) and mating nuts.

I printed the parts in their default orientation without support, but they may print better or worse flipped horizontally 180 degrees. Either way, clean up any loose strands on the overhangs.

The attached Fusion360 file is for an earlier version of the collar. I was unable to recover the latest version after my computer crashed, so there is no pocket for nuts to go with the screws, there aren't proper internal clearances at both the top and bottom, and there is no pocket for the Fly6 taillight. The taillight would still fit since it has a long strap, but the rubber cradle would get stretched around the 40mm diameter of the collar instead of the 27.2 curve of the pocket in the STL file.