Ben's Better Dropper Post Seat Bag Adapters (26.4, 22, and 22 tall)

I designed this specifically for a 26.4 mm diameter stanchion dropper post for 1" straps, and later added a version for a 22 mm stanchion dropper post, both for 1" and 2" straps based on the requests of others. I had earlier purchased a couple of these similar products from Wolftooth, but when my 25 mm OD stock Bontrager dropper post failed on one of my bikes, I replaced it with a 2021 Fox Transfer dropper post, and then made the same upgrade for my other bike. Then when I went to use the clamp with my Revelate Vole seat bag, I discovered that the clamp would not work. Rather than buying another pair of the 26mm version for another $50, which may or may not have worked, I designed and made my own. My version is much easier to install due to its two piece design. The Wolftooth product is a very stiff plastic that is very hard to slide over the post. I often ended up pinching myself or scratching the post. My version also keeps a stronger hold with less pressure on the post due to the rubber interface, and two screw setup. You might think that the extra pieces would make it difficult to install, but it's actually fairly easy, since I added a small ledge to hold the rubber strip in place.  The washers are a tight enough fit to hold in place. My version still goes around the stanchion seal to ensure it does not damage them or push dirt into it. It can also be used as an emergency locking ring if you have a mechanical issue that prevents the dropper post from staying extended. It will work with other seat bags with straps up to 1" wide, and could be modified to work with wider straps (one 2" strap version added as of 3-15-23). I have provided STLs for other stanchion diameters and/or strap widths upon request, but I would encourage you to modify the design from the provided Fusion 360 file if needed and share the results here.

Edit 1-30-22: I have added STLs for a 22mm stanchion, 27.2mm seat tube diameter PNW Coast dropper post upon request from a few people. It has not been tested yet. I may update the CAD model later to fix some minor issues I discovered that make it difficult to modify it.

Edit 1-31-22: I have uploaded new 3mf (and gcode) files to simplify things. It only added a couple of minutes and grams to just go with a solid print. I renamed the other files for clarity. I'll add more info as things are tested and refined.

Edit 3-15-23: I uploaded the 2" strap version, and tweaked the diameter clamping margin parameter on the existing models to ease assembly and improve fit and function slightly. This updated version was tested and it works well. The tall version is similar to the 2" remix someone posted just recently, though theirs uses hex nuts, so that variation might be worth testing if it makes things easier to assemble and is still strong enough. Uploaded new models, gcode, and 3mf files, plus more make photos.

The parts list is as follows:

• 1.5mm (1/16") silicone rubber in a 75 mm x 25mm strip (note that the 22mm stanchion adapter will require a shorter length of 61 mm) - (I found a 12x12 sheet on Amazon and cut to size)
• qty. 2 - M4 x 20mm socket head cap screw, with optional 8.8mm OD washers (I bought a Vigrue kit on Amazon. Button head cap screws would also work, but I wanted to have the larger, more common 3mm key size of the SHCS.)
• qty. 2 -  M4 x 8mm brass threaded insert (I bought this set)
• Black PETG filament for flexibility, toughness, and UV resistance

I bought the hardware in multi-size kits on Amazon, but you can also source them separately from a hardware distributor such as McMaster Carr. The soldering iron tips for the threaded inserts are available in both places, but are more expensive on McMaster and one I bought there was too wide to work in tighter spaces. You may be able to get away with a standard conical tip of the right proportions. There are plenty of tutorials out there if you need help with that process, such as this one.