Improved Water Bottle Holder for Flexible Bottles

I love riding my bike. It is always relaxing to pedal around the neighborhood or go off-road on scenic hiking trails, and it makes for great exercise. Whenever I go biking, I always carry a bottle of water with me, because one of the most important parts of biking is staying hydrated. Most bikes come equipped with a water bottle holder in the center of the frame, where the bottle can sit while riding and then easily removed to drink from. On my bike, however, the holder is of a simple design made from wire, and because of that, the water bottle holder can only accommodate medium-sized, reusable sports bottles. This poses a problem when I use a more flexible, plastic bottle, because the more I drink from it the more the bottle is able to be compressed. After about half the water is drunk, the bottle no longer fits in the holder and falls out when biking. With this project, I sought to solve that problem by designing, modeling, and printing my own improved custom water bottle holder complete with a compliant-mechanism-based spring to ensure that the bottle is always held securely.

• For this project, the supplies were fairly simple. I used a set of digital calipers to take the measurements, and my Ender 3 V2 to print the final model. You can use any filament as long as it is rigid but not so brittle that it cannot bend (PLA, ABS, and PETG are perfect; Avoid overly flexible filaments like TPU).

To get an idea of how the water bottle holder would mount to my bike, I first measured the diameter of the mounting screws used with the old holder, and how far apart the mounting points were. I also measured the diameter of the heads of the screws, so I could add counter-sinks into the frame of the holder.

For creating the 3D model, I chose to use Fusion because the complex geometry sketch tools allowed me to create exact curve profiles and chamfers. To start the design process, I modeled the mounting plate for my holder to be built on. I made the base curved so that it would fit securely to the frame of the bike and not shift around on bumps or turns. I then added counter sinks for the screws, so that they would sit flush with the mounting plate.

For this design, I wanted to experiment with compliant mechanisms for the spring component. After researching several different styles, I settled on a simple but durable hinge design that would maintain strong tension on the water bottle, while also being easy to pull back when grabbing the bottle. The spring was designed to be naturally in the fully closed position so the clip can maintain tension on smaller bottles. The end of the clip is also curved, to maintain maximum contact with the bottle. If you would like to print a water bottle holder of your own, check out the files below.

For the print, I decided to go with Overture PLA for the filament because it prints well and is flexible enough for the spring while not being too brittle that it snaps. I printed the model on 20 percent infill, with a raft for bed adhesion. The model was designed to require no supports, and if printed in the upright orientation, it has no overhangs that cannot be bridged.

Once my print was finished, I removed the bolts from the old holder and screwed on the new one. It works amazingly, and the curvature of the mount perfectly fits that of the frame. The spring is slightly on the stiffer side, but after a little use, it should bend more easily. This project was a great lesson for me in advanced CAD techniques and the wonderful world of compliant mechanisms, and I hope you can enjoy it too.