The seed for this project was the desire to mechanically measure specific amounts of liquid in a way that was both adjustable and easy to clean. In the past, I have used measured pour spouts on cocktail machines, and they work fine, but they are not adjustable and occasionally they just stop working.
I started by thinking about the Japanese Shishi-Odoshi ("deer scarer") bamboo fountain feature, which measures liquid against a counterweight and pours when the liquid reaches a certain level. The system is wonderfully simple, with one big caveat: the liquid never stops pouring.
So I began prototyping on a piece of plywood with a plastic cup. I new that the receptacle had to be lightweight, so that the liquid would make up the majority of the total weight and be easier to fine tune the "cut off" point for the pouring. I discovered that the pouring mechanism would actually need four parts:
When the cup is lifted, it pushes the Lock Arm up, releasing liquid. As the Lock Arm lifts, the Counterweight Arm lifts also and the two lock together. The hook from the Counterweight Arm is now holding the cup up. When the cup fills with enough liquid to overpower the Counterweight Arm, it pulls free of the hook and pours, while the Counterweight Arm pulls free of the Lock Arm and the bottle is sealed again.
It pretty much works. A little leaky, but overall a great first step.
After the initial Proof-of-Concept prototype, I wanted to make a more formal test. I ordered some parts, including a bottle from McMaster Carr, and began modelling the pouring mechanism in Solidworks.
The bottle, Mcmaster #4787T64, was a Kimax lab glass bottle, and made me think of a Mad Scientist Chemistry Experiment type theme. So I started planning how I could make the final product fit this theme. I liked the images of chemistry kits with different components clamped to vertical stands, and lots of busy parts crossing from here to there. This theme lends itself to producing the machine in mostly stainless steel, which would make it easy to clean and maintain, so I ran with it.
I found another McMaster part, Quick Clamp Sanitary Tube Fittings (#45195K44) that would work great for clamping to 3/4" diameter tubing, and could have parts welded to it. You can see it modeled in the CAD screenshot above.
I decided that the machine would make Manhattans, mostly just because I like Manhattans. The ingredients are, roughly: 2 parts Bourbon, 1 part Sweet Vermouth, and a dash of bitters. I knew I would use two "Pouring Modules" for the Bourbon and Vermouth, so I began trying to figure out how to deliver the bitters, etc.