I wanted to build something that I would use myself for the bike accessory contest. I needed a bottle holder, so voila! The problem I had was I had an "old school" bottle with a 94mm diameter. I was telling my sister about the design, and she requested I build one for her as well since her tea bottle didn't fit either.
Apparently the standard size holder is actually one size fits none! It seemed there were a lot of people looking for custom sized holders for their bike, so I decided to make a modular system that can accommodate any sized or shaped bottle that could reasonable fit in that location. I built this with rails that should fit snug. The "spine" is attached to the bicycle and two "wings" are slid into place. The nut/bolt size is 1/2", ~3mm deep. Slide the "wings" back out and replace with another set.
I do have a few more "wing" designs but I wanted to keep the original idea short and simple for this contest. I added the reinforced "wing" because it turned out to be so versatile. It is a bit harder to slide on the rail and it barely fits the 94mm bottle, but it is very snug and secure. This will still be for larger than normal bottles.