A hinged bracket for supporting a handlebar extender tube/cylinder above Brompton curved handlebars on M and H models such as an H6R. An extender gives you more “handlebar” space to mount things like headlights, phones, e-bike controls, bike computers, etc.

Most handlebar extenders seem to be designed for use with straight handlebars. The brackets must attach to a flat part (so the middle) and aren't long enough to reach from bottom of the valley up and over the horizontal ends. Plus they interfered with my Swytch battery holder.

For the STL, both the handlebars and the extension should be 22.2mm. If either is different you can use the OpenSCAD script and update the variables.

For the extender cylinder, you can print a 22.2mm cylinder of the length of your choosing, or buy one. I wanted one that doubles as a USB charger so I got this (and threw away the brackets): https://www.amazon.com/gp/product/B09DPLG71D/

v4 is sized for the lower part to be as high as possible on the handlebars (close to the shifters) and the extender just above the level outer parts of the handlebars, as far apart (close to the ends of the extender) as possible. (The pictures are of v3, which was slightly longer.)

To print, clone the part and mirror one along the longest axis, then split each copy into two parts, and pull them away from each other. The hinge is not designed to print in place. The clamps have slightly more clearance so they should have a gap on a well-tuned printer. If yours fuse, use the OpenSCAD script and increase slop.

I recommend a strong material. I used Prusament PC Blend (in Prusa orange to match my Brompton) but ABS or PETG is probably fine. Nylon is probably too flexible and PLA would probably deform over time.

Slice strong, such as 3-4 walls and 25% Cubic or Gyroid infill. No support is needed.

For hardware you'll need:

• 6x M4x18mm socket cap bolts with 7mm wide and 4mm tall head (22mm overall length)
• 6x M4 nuts that are 6.9mm between the flats and 3.1mm thick

If your hardware has different dimensions, you can use the OpenSCAD script and update the variables. Also I didn't use any washers and the STL isn't sized to accept them.

I wasn't sure how stable it would be but it's rock-solid. I think having the rings/clamps at nearly right angles instead of parallel helps because they can just spin.

Update 5/21/23: I found that v4 was unstable because of the shorter length and reduced material so I made it wider and thicker in v6, which stabilized it. Pictures are still v3.