This was arguably one of the harder parts of the design to get dialed in. To recap from the last post (here if you missed it) we knew it had to fit my 40 oz water bottle at the largest, had to have some kind of beverage gripping system and to top it off leave room at the front to plug in a USB charger. So let's start with two holes large enough for my water bottle and figure out the space needed to house the gripping mechanism and what that mechanism would even look like. At first we aim for the moon. I wanted something different, something with semicircular arms that could rotate in and lock the beverage in place. This solution would leave the user with almost endless adjustability, the arm would just rotate in the meet any size container. I spent hours trying to figure out how that would work, where the springs would go, how could it be made in a way that it was even feasible to manufacture…
It turns out this was the first of many ideas to get thrown to the curb. Not only was it not going to fit anywhere in the footprint of the cup holder but it was going to be very difficult to manufacture and get it to work without any frustration for the user. Many cup holders have little flip up arms, can't be a coincidence they all do it this way right? But I still wanted this to be better, it had to be sized just right and designed with more in mind. So now back to my other beverage options, 12oz Redbull can, 20oz iced coffee (I live on caffeine and water), so using these two containers I could determine the size of the spring loaded arms. Done, right?... for fitment maybe but we will come back to this in a later post. So now we know the size and style of the device that will be used to restrain the containers.
well when the arms are fully extended they have lots of strength as you are not relying on the spring to hold the beverage in place but rather putting all of the force into the arm. What if it’s a container size different from these 3? Well then the equation gets more complicated, you have to consider the length of the arm, the force of the spring, and the fiction between the beverage container and base of the cup holder. We have defined one of these, one we cannot control and the other is where the next design element will be found, length of the arm (defined), interaction between the container and the base of the cup holder (too hard to define, we could pick some common materials to design around but ultimately its an unknown), spring rate (now this is something we can work with)
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